248 results on '"Lars Kloo"'
Search Results
2. Insights into the Explicit Mechanism and Dynamic Rate of Regeneration of Sensitizing Organic Dyes by Transition-Metal Redox Mediators in Solar Cells Using Ab Initio Molecular Dynamics
- Author
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Lanlan He, Yu Guo, and Lars Kloo
- Subjects
Materials Chemistry ,Electrochemistry ,Energy Engineering and Power Technology ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering - Published
- 2022
3. An Ab Initio Molecular Dynamics Study of the Mechanism and Rate of Dye Regeneration by Iodide Ions in Dye-Sensitized Solar Cells
- Author
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Lanlan He, Yu Guo, and Lars Kloo
- Subjects
Renewable Energy, Sustainability and the Environment ,General Chemical Engineering ,Environmental Chemistry ,General Chemistry - Published
- 2022
4. On the non-existence of a square-planar pentaiodide coordination complex I(<scp>i</scp>)4−
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Lars Kloo
- Subjects
Inorganic Chemistry - Abstract
The coordination complex form of the pentaiodide ion represents a meta-stable isomer of the ubiquitous and archetypical V-shaped I5− ion, although it so far has not been identified in any isolated polyiodide compound.
- Published
- 2022
5. Water-in-salt electrolytes – molecular insights to the high solubility of lithium-ion salts
- Author
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Aleksandar Tot and Lars Kloo
- Subjects
Materials Chemistry ,Metals and Alloys ,Ceramics and Composites ,General Chemistry ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
The recently established water-in-salt electrolyte (WISE) concept indicates the possible application of aqueous electrolytes in lithium-ion batteries (LiBs). The application of this type of highly concentrated electrolyte relies on a proper understanding of their thermodynamically stable solutions. Therefore, fundamental insights regarding the Li[TFSI] solubility in water are important for the rational design of reproducible and stable WISE.
- Published
- 2022
6. Sodium to cesium ions: a general ladder mechanism of ion diffusion in prussian blue analogs
- Author
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Johan Nordstrand, Esteban Toledo-Carrillo, Lars Kloo, and Joydeep Dutta
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Fysikalisk kemi ,General Physics and Astronomy ,Physical and Theoretical Chemistry ,Physical Chemistry - Abstract
Prussian blue analogs (PBAs) form crystals with large lattice voids that are suitable for the capture, transport and storage of various interstitial ions. Recently, we introduced the concept of a ladder mechanism to describe how sodium ions inside a PBA crystal structure diffuse by climbing the frames formed by aligned cyanide groups in the host structure. The current work uses semi-empirical tight-binding density functional theory (DFTB) in a multiscale approach to investigate how differences in the size of the monovalent cation affect the qualitative and quantitative aspects of the diffusion process. The results show that the ladder mechanism represents a unified framework, from which both similarities and differences between cation types can be understood. Fundamental Coulombic interactions make all positive cations avoid the open vacant areas in the structure, while cavities surrounded by partially negatively charged cyanide groups form diffusion bottlenecks and traps for larger cations. These results provide a new and quantitative way of understanding the suppression of cesium adsorption that has previously been reported for PBAs characterized by a low vacancy density. In conclusion, this work provides a unified picture of the cation adsorption in PBAs based on the newly formulated ladder mechanism. QC 20221125
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- 2022
7. Electrostatic interactions and physisorption: mechanisms of passive cesium adsorption on Prussian blue
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Johan Nordstrand and Lars Kloo
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General Physics and Astronomy ,Physical and Theoretical Chemistry ,Other Natural Sciences ,Annan naturvetenskap - Abstract
The dangers posed by nuclear accidents necessitate developments in techniques for cesium removal. One such is the adsorption of cesium cations in Prussian blue (PB) materials, on which adsorption can be a substation process or pure physisorption. The underlying mechanism of the latter is not well understood, although a Langmuir isotherm is frequently used to model experimental results. In this work, we exploit tight-binding density-functional theory (DFTB) methods to probe the atomic interactions in the physisorption process. The results show that there is a diminishing return for the energy of adsorption as more sites are filled. This means that the adsorption sites are not independent, as stipulated by the ideal Langmuir isotherm. Instead, the results indicate that electrostatic effects need to be considered to explain the theoretical and experimental results. Therefore, an electrostatic Langmuir (EL) model is introduced, which contains an electrostatic ideality correction to the classic Langmuir isotherm. For future materials development, these physical insights indicate that shielding effects as well as the number of independent physical sites must be considered when synthesizing effective Prussian blue analogs (PBA). In conclusion, the study provides insights into the limiting mechanisms in the physisorption of cesium cations on PB. QC 20221201
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- 2022
8. Robotised screening and characterisation for accelerated discovery of novel Lithium-ion battery electrolytes : Building a platform and proof of principle studies
- Author
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Per H. Svensson, Pavel Yushmanov, Aleksandar Tot, Lars Kloo, Erik Berg, and Kristina Edström
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Lithium-ion ,Fysikalisk kemi ,Batteries ,Electrolytes ,Energy storage ,General Chemical Engineering ,Materials Chemistry ,Environmental Chemistry ,Materialkemi ,Robotised screening ,General Chemistry ,Physical Chemistry ,Industrial and Manufacturing Engineering - Abstract
A fast transition towards the use of clean and green energy sources requires accelerated discovery of new energy storage systems and devices. In this concept automation and robotics can play a key role. Here we present the development of a robotized platform, Poseidon, for the screening and discovery of new water-based electrolyte candidate systems for lithium-ion batteries (LIBs) systems. We have successfully demonstrated the Poseidon screening and characterisation capabilities for electrolytic discovery, which includes a range of steps such as electrolyte formulation, Raman spectroscopic characterization, coin-cell mounting/disassembling and electro-chemical battery evaluation via an accelerated screening cycling procedure. A comparison with analogous manual laboratory experiments shows that relevant accuracy for robotized screening purposes has been estab-lished. Furthermore, the presented accelerated charge/discharge cycling procedure is shown to be adequate for screening purposes of the test system.
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- 2023
9. Catenated compounds in group 17—polyhalides
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Lars Kloo
- Published
- 2023
10. Water-in-salt electrolytes made saltier by Gemini ionic liquids for highly efficient Li-ion batteries
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Aleksandar Tot, Leiting Zhang, Erik J. Berg, Per H. Svensson, and Lars Kloo
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Energiteknik ,Fysikalisk kemi ,Inorganic Chemistry ,Oorganisk kemi ,Multidisciplinary ,Materials Chemistry ,Materialkemi ,Energy Engineering ,Condensed Matter Physics ,Den kondenserade materiens fysik ,Physical Chemistry - Abstract
The water-in-salt electrolytes have promoted aqueous Li-ion batteries to become one of the most promising candidates to overcome safety concerns/issues of traditional Li-ion batteries. A simple increase of Li-salt concentration in electrolytes can successfully expand the electrochemical stability window of aqueous electrolytes beyond 2 V. However, necessary stability improvements require an increase in complexity of the ternary electrolytes. Here, we have explored the effects of novel, Gemini-type ionic liquids (GILs) as a co-solvent systems in aqueous Li[TFSI] mixtures and investigated the transport properties of the resulting electrolytes, as well as their electrochemical performance. The devices containing pyrrolidinium-based GILs show superior cycling stability and promising specific capacity in the cells based on the commonly used electrode materials LTO (Li4Ti5O12) and LMO (LiMn2O4).
- Published
- 2023
11. On the non-existence of a square-planar pentaiodide coordination complex I(I)
- Author
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Lars, Kloo
- Abstract
The properties of two conformers of the pentaiodide ion, a V-shaped and regularly observed I
- Published
- 2022
12. On closed-shell interactions between heavy main-group elements
- Author
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Lars Kloo
- Subjects
Computational Mathematics ,Physics::Atomic and Molecular Clusters ,General Chemistry - Abstract
A series of di- and polymetal complexes involving closed-shell, heavy main-group atoms and ions shows a selection of special physical properties. These involve short metal-metal contacts, low entropies of formation and, most interestingly, strong Raman bands at low wavenumbers. These results together with the constitution of the coordination compounds, where the majority of electrons are assembled on the highly polarizable metal atoms and ions, experimental results have been interpreted in terms of direct, partial covalent metal-metal bonding. Previous theoretical studies have challenged this view and instead attributed the obvious attractive forces involved to secondary-type of interactions, such as dispersion. This study utilizes a multitude of theoretical tools, such as natural bond order (NBO) and natural energy decomposition analysis (NEDA), non-covalent interaction (NCI) analysis, electron localization functions (ELFs), and atoms-in-molecules (AIM) to characterize the interactions in models comprising closed-shell dimers, as well as experimentally studied ring and cage systems constituting the main reason for the hypotheses on metal-metal interactions. The results show that all experimental results can be attributed to the covalent interactions between the electron-rich, metal centers and the bridging anions in ring and cage coordination compounds of high symmetry, where the experimentally observed effects can be traced to the combination of covalent interactions between the metal centers and the anions along the edges of the ring and cage systems in combination with the cooperative effects generated by the high symmetry of these ring and cage systems.
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- 2022
13. Electrochemical impedance and X-ray absorption spectroscopy analyses of degradation in dye-sensitized solar cells containing cobalt tris(bipyridine) redox shuttles
- Author
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Jiajia Gao, Aleksandar Tot, Haining Tian, James M. Gardner, Dibya Phuyal, and Lars Kloo
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Fysikalisk kemi ,General Physics and Astronomy ,Physical and Theoretical Chemistry ,Physical Chemistry - Abstract
Electrochemical impedance spectroscopy (EIS) is a commonly used steady-state technique to examine the internal resistance of electron-transfer processes in solar cell devices, and the results are directly related to the photovoltaic performance. In this study, EIS was performed to study the effects of accelerated ageing, aiming for insights into the degradation mechanisms of dye-sensitized solar cells (DSSCs) containing cobalt tris(bipyridine) complexes as redox mediators. Control experiments based on aged electrolytes differing in concentrations of the redox couple components and cation co-additives were conducted to reveal the correlation of the cell degradation with external and internal properties. The failure modes of the cells emerged as changes in the kinetics of charge- and ion-transfer processes. An insufficient concentration of the redox complexes, in particular Co(iii), was found to be the main reason for the inferior performance after ageing. The related characterization of electrolytes aged outside the solar cell devices confirms the loss of active Co(iii) complexes in the device electrolytes. A new EIS feature at low frequencies emerged during ageing and was analysed. The new EIS feature demonstrates the presence of an unexpected rate-limiting, charge-transfer process in aged devices, which can be attributed to the TiO2/electrolyte interface. High-resolution fluorescence detected X-ray absorption spectroscopy (HERFD-XAS) was performed to identify the reduction of a part of Co(iii) to Co(II) after ageing, by investigating the Co K absorption edge. The HERFD-XAS data suggested a partial reduction of Co(iii) to Co(ii), accompanied by a difference in symmetry of the reduced species.
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- 2022
14. Necessity of structural rearrangements for O O bond formation between O5 and W2 in photosystem II
- Author
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Biaobiao Zhang, Lars Kloo, Yu Guo, and Licheng Sun
- Subjects
Photosystem II ,Chemistry ,Stereochemistry ,Energy Engineering and Power Technology ,Substrate (chemistry) ,02 engineering and technology ,Bond formation ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Fuel Technology ,Catalytic cycle ,Electrochemistry ,Cluster (physics) ,0210 nano-technology ,Energy (miscellaneous) - Abstract
Numerous aspects of the water oxidation mechanism in photosystem II have not been fully elucidated, especially the O O bond formation pathway. However, a body of experimental evidences have identified the O5 and W2 ligands of the oxygen-evolving complex as the highly probable substrate candidates. In this work, we studied O O bond formation between O5 and W2 based on the native Mn4Ca cluster by density functional calculations. Structural rearrangements before the formation of the S4 state were found as a prerequisite for O O bond formation between O5 and W2, regardless if the suggested pathways involving the typical Mn1(IV)-O species or the recently proposed Mn4(VII)(O)2 species. Possible alternatives for the S2 → S3 and S3 → S4 transitions accounting for such required rearrangements are discussed. These findings reflect that the structural flexibility of the Mn4Ca cluster is essential to allow structural rearrangements during the catalytic cycle.
- Published
- 2021
15. Reversible Structural Isomerization of Nature's Water Oxidation Catalyst Prior to O-O Bond Formation
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Yu Guo, Johannes Messinger, Lars Kloo, and Licheng Sun
- Subjects
Fysikalisk kemi ,Organisk kemi ,Oorganisk kemi ,Manganese ,photosynthesis ,Organic Chemistry ,Biophysics ,Photosystem II Protein Complex ,Water ,General Chemistry ,Ligands ,Physical Chemistry ,Biochemistry ,Biofysik ,Catalysis ,Inorganic Chemistry ,Oxygen ,Colloid and Surface Chemistry ,water oxidation ,Isomerism ,Teoretisk kemi ,O-O bond formation ,Theoretical Chemistry ,Oxidation-Reduction - Abstract
Photosynthetic water oxidation is catalyzed by a manganese–calcium oxide cluster, which experiences five “S-states” during a light-driven reaction cycle. The unique “distorted chair”-like geometry of the Mn4CaO5(6) cluster shows structural flexibility that has been frequently proposed to involve “open” and “closed”-cubane forms from the S1 to S3 states. The isomers are interconvertible in the S1 and S2 states, while in the S3 state, the open-cubane structure is observed to dominate inThermosynechococcus elongatus (cyanobacteria) samples. In this work, using density functional theory calculations, we go beyond the S3+Yz state to the S3nYz• → S4+Yz step, and report for the first time that the reversible isomerism, which is suppressed in the S3+Yz state, is fully recovered in the ensuing S3nYz• state due to the proton release from a manganese-bound water ligand. The altered coordination strength of the manganese–ligand facilitates formation of the closed-cubane form, in a dynamic equilibrium with the open-cubane form. This tautomerism immediately preceding dioxygen formation may constitute the rate limiting step for O2 formation, and exert a significant influence on the water oxidation mechanism in photosystem II. Swedish Research Council 2020-03809
- Published
- 2022
16. A crosslinked polymer as dopant-free hole-transport material for efficient n-i-p type perovskite solar cells
- Author
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Yu Guo, Lanlan He, Tianqi Liu, Xichuan Yang, James M. Gardner, Linqin Wang, Lars Kloo, Licheng Sun, Yuanyuan Li, Bin Cai, Bo Xu, Fuguo Zhang, and Wei Zhang
- Subjects
chemistry.chemical_classification ,Solid-state chemistry ,Materials science ,Dopant ,Energy Engineering and Power Technology ,02 engineering and technology ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Fuel Technology ,Chemical engineering ,chemistry ,Thermal ,Electrochemistry ,0210 nano-technology ,Energy (miscellaneous) ,Perovskite (structure) - Abstract
A new crosslinked polymer, called P65, with appropriate photo-electrochemical, opto-electronic, and thermal properties, has been designed and synthesized as an efficient, dopant-free, hole-transpor ...
- Published
- 2021
17. Ionic Liquid Synthesis of (Et 3 S)[Ag 4 I 5 ] – A Structure Containing Basket‐Like Silver‐Iodide Cages with Ag 2 2+ Pairs
- Author
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Per H. Svensson and Lars Kloo
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Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,Ionic liquid ,Silver iodide ,Crystal structure ,Host–guest chemistry ,Electronic band structure - Published
- 2021
18. The dynamics of light-induced interfacial charge transfer of different dyes in dye-sensitized solar cells studied by ab initio molecular dynamics
- Author
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Lars Kloo, Lanlan He, and Yu Guo
- Subjects
Materials science ,General Physics and Astronomy ,Electrolyte ,Dihedral angle ,Ion ,Solvent ,Dye-sensitized solar cell ,chemistry.chemical_compound ,Reaction rate constant ,chemistry ,Chemical physics ,Carboxylate ,Physical and Theoretical Chemistry ,Solvent effects - Abstract
The charge-transport dynamics at the dye–TiO2 interface plays a vital role for the resulting power conversion efficiency (PCE) of dye sensitized solar cells (DSSCs). In this work, we have investigated the charge-exchange dynamics for a series of organic dyes, of different complexity, and a small model of the semiconductor substrate TiO2. The dyes studied involve L1, D35 and LEG4, all well-known organic dyes commonly used in DSSCs. The computational studies have been based on ab initio molecular dynamics (aiMD) simulations, from which structural snapshots have been collected. Estimates of the charge-transfer rate constants of the central exchange processes in the systems have been computed. All dyes show similar properties, and differences are mainly of quantitative character. The processes studied were the electron injection from the photoexcited dye, the hole transfer from TiO2 to the dye and the recombination loss from TiO2 to the dye. It is notable that the electronic coupling/transfer rates differ significantly between the snapshot configurations harvested from the aiMD simulations. The differences are significant and indicate that a single geometrically optimized conformation normally obtained from static quantum-chemistry calculations may provide arbitrary results. Both protonated and deprotonated dye systems were studied. The differences mainly appear in the rate constant of recombination loss between the protonated and the deprotonated dyes, where recombination losses take place at significantly higher rates. The inclusion of lithium ions close to the deprotonated dye carboxylate anchoring group mitigates recombination in a similar way as when protons are retained at the carboxylate group. This may give insight into the performance-enchancing effects of added salts of polarizing cations to the DSSC electrolyte. In addition, solvent effects can retard charge recombination by about two orders of magnitude, which demonstrates that the presence of a solvent will increase the lifetime of injected electrons and thus contribute to a higher PCE of DSSCs. It is also notable that no simple correlation can be identified between high/low transfer rate constants and specific structural arrangements in terms of atom–atom distances, angles or dihedral arrangements of dye sub-units.
- Published
- 2021
19. Influence of TiO2 surface defects on the adsorption of N719 dye molecules
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Altaf A. Shamsaldeen, Christopher T. Gibson, Lars Kloo, Sunita Gautam Adhikari, Yanting Yin, and Gunther G. Andersson
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Adsorption ,Materials science ,X-ray photoelectron spectroscopy ,Sputtering ,Density of states ,General Physics and Astronomy ,Substrate (electronics) ,Physical and Theoretical Chemistry ,Photochemistry ,Spectroscopy ,Electron spectroscopy ,Ultraviolet photoelectron spectroscopy - Abstract
Surface defects influence the dye adsorption on TiO2 used as a substrate in dye-sensitized solar cells (DSSCs). In this study, we have used different Ar+ sputtering doses to create a controlled density of defects on a TiO2 surface exposed to different pre-heating temperatures in order to analyse the influence of defects on the N719 dye adsorption. TiO2 was pre-treated using two different treatments. The first treatment involved heating to 200 °C with subsequent sputtering at different doses. The second treatment included heating only, but at four different temperatures starting at 200 °C. After the pre-treatments, the TiO2 samples were immersed into an N719 dye solution for 24 hours at room temperature to dye the TiO2 substrates. The amount of Ti3+ surface defects introduced by the different pre-treatments and their influence on dye adsorption onto the TiO2 surface were examined by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and metastable induced electron spectroscopy (MIES). Neutral impact collision ion scattering spectroscopy (NICISS) was used to determine the coverage of the TiO2 surface by adsorbed dye molecules. It was found that Ti3+ surface defects were formed by Ar+ sputtering but not by pre-treatment through heating alone. MIES analysis of the outer-most layer and density of states calculations show that the thiocyanate ligand of the N719 dye becomes directed away from the TiO2 surface. Both XPS and NICISS results indicate that the amount of adsorbed N719 dye decreases with increasing density of Ti3+ surface defects. Thus, the generation of surface defects reduces the ability of the TiO2 surface to adsorb the dye molecules. Heating alone as pre-treatment of the TiO2 substrates instead increases the dye adsorption, without causing detectable defects on the TiO2 surface.
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- 2021
20. Comparison between Benzothiadizole–Thiophene- and Benzothiadizole–Furan-Based D–A−π–A Dyes Applied in Dye-Sensitized Solar Cells: Experimental and Theoretical Insights
- Author
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Walid Sharmoukh, Nageh K. Allam, Jiayan Cong, Lars Kloo, and Basant A. Ali
- Subjects
Materials science ,General Chemical Engineering ,Energy conversion efficiency ,General Chemistry ,Conjugated system ,Photochemistry ,Acceptor ,Article ,Chemistry ,chemistry.chemical_compound ,Dye-sensitized solar cell ,chemistry ,Furan ,Thiophene ,QD1-999 ,Linker ,HOMO/LUMO - Abstract
Three novel donor–acceptor−π–acceptor-type compounds (WS5, WS6, and WS7) were synthesized and investigated in dye-sensitized solar cells (DSSCs) exploring the effect of conjugated linkers on device performance. The new dyes showed strong light-harvesting ability in the visible region with relatively high molar absorption coefficients (>21 800 M–1 cm–1). This can be attributed to their intrinsic charge transfer (CT) from the arylamine to the acceptor group. Density functional theory (DFT) calculations revealed a favorable lowest unoccupied molecular orbital (LUMO) energy level, allowing efficient injection into the semiconductor conduction band after excitation. Upon application in DSSC devices, the WS5 dye containing 4,7-di(furan-2-yl)benzo[c][1,2,5]thiadiazole as conjugated linker mediated the highest device power conversion efficiency (PCE) amounting to 5.5%. This is higher than that of the WS6-containing dye based on the 4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole linker (3.5%) and the WS7 dye based on the 4-(thiophen-2-yl)benzo[c][1,2,5]thiadiazole linker (4.3%) under AM 1.5 G illumination. The present results show furan-based dye linker systems to have a significant potential for improving DSSC efficiencies.
- Published
- 2020
21. Organic Salts as p-Type Dopants for Efficient LiTFSI-Free Perovskite Solar Cells
- Author
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Biaobiao Zhang, Yu Guo, Linqin Wang, Yuanyuan Li, Fuguo Zhang, James M. Gardner, Wei Zhang, Licheng Sun, Lars Kloo, and Bo Xu
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Materials science ,p-type dopant ,chemistry.chemical_element ,Perovskite solar cell ,LiTFSI-free ,02 engineering and technology ,Conductivity ,010402 general chemistry ,01 natural sciences ,law.invention ,law ,Solar cell ,General Materials Science ,Perovskite (structure) ,hole-transport material ,Dopant ,Doping ,stability ,021001 nanoscience & nanotechnology ,perovskite solar cell ,0104 chemical sciences ,chemistry ,Chemical engineering ,organic salt ,Lithium ,0210 nano-technology ,Cobalt ,Research Article - Abstract
Despite the ubiquity and importance of organic hole-transport materials in photovoltaic devices, their intrinsic low conductivity remains a drawback. Thus, chemical doping is an indispensable solution to this drawback and is essentially always required. The most widely used p-type dopant, FK209, is a cobalt coordination complex. By reducing Co(III) to Co(II), Spiro-OMeTAD becomes partially oxidized, and the film conductivity is initially increased. In order to further increase the conductivity, the hygroscopic co-dopant LiTFSI is typically needed. However, lithium salts are normally quite hygroscopic, and thus, water absorption has been suggested as a significant reason for perovskite degradation and therefore limited device stability. In this work, we report a LiTFSI-free doping process by applying organic salts in relatively high amounts. The film conductivity and morphology have been studied at different doping amounts. The resulting solar cell devices show comparable power conversion efficiencies to those based on conventional LiTFSI-doped Spiro-OMeTAD but show considerably better long-term device stability in an ambient atmosphere.
- Published
- 2020
22. Implicit tandem organic–inorganic hybrid perovskite solar cells based on internal dye sensitization: Robotized screening, synthesis, device implementation, and theoretical insights
- Author
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Per H. Svensson, Allan Starkholm, and Lars Kloo
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Photocurrent ,Tandem ,Chemistry ,business.industry ,Energy conversion efficiency ,Photovoltaic system ,Nanotechnology ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,Article ,0104 chemical sciences ,law.invention ,Characterization (materials science) ,Colloid and Surface Chemistry ,law ,Photovoltaics ,Solar cell ,business ,Perovskite (structure) - Abstract
Low-dimensional hybrid perovskite materials offer significantly improved stability as well as an extensive compositional space to explore. However, they suffer from poor photovoltaic performance as compared to the 3D perovskite materials because of poor charge-transport properties. Herein, we present the concept of internal dye-sensitized hybrid perovskite compounds involving five novel low-dimensional perovskite-type materials 1-5 incorporating triarylmethane, phenazinium and near-infrared (NIR) cyanine cationic dyes, respectively. The synthesis characterization and theoretical analysis of these compounds are presented. Theoretical calculations provide interesting insights into the effects of these dyes on the band structure of the low-dimensional anionic metal-halides and especially highlight compound 1 as a promising photovoltaic candidate. Solar cell investigation of devices based on 1 were conducted. The results show an average power conversion efficiency (PCE) of about 0.1%, which is among the highest reported for a 1D material despite the use of undoped Spiro-OMeTAD as the hole-transport material (HTM). Incident photon-to-electron efficiency (IPCE) spectra confirm the contribution of the dye to the overall photocurrent of the solar cell. Moreover, examination of solar cell devices based on the bismuth-based compound 5 resulted in PCEs in the range of 0.1%. This illustrates the potential of this concept to be exploited for lead-free photovoltaics. Finally automated robotized screening of low-dimensional hybrid perovskite materials through the screening robot PROTEUS has emerged as a powerful tool in the search for novel perovskite-like materials. Our work highlights that the use of cationic dyes could induce interesting sensitizing properties to low-dimensional metal-halide chains and may therefore provide inspiration and new design strategies for the synthesis of new lead-free photovoltaic materials.
- Published
- 2020
23. Single crystal structure and opto-electronic properties of oxidized Spiro-OMeTAD
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James M. Gardner, Zhuofeng Li, Yu Guo, Linqin Wang, Lars Kloo, Biaobiao Zhang, Wei Zhang, Licheng Sun, Valentina Leandri, and Bo Xu
- Subjects
Valence (chemistry) ,Materials science ,Metals and Alloys ,Kemi ,General Chemistry ,Orbital overlap ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Crystallography ,Chemical Sciences ,Materials Chemistry ,Ceramics and Composites ,Opto electronic ,Electronic band structure ,Single crystal ,Electronic properties - Abstract
Single crystals of Spiro(TFSI)2 were grown, the optical and electronic properties were characterized and compared with neutral Spiro-OMeTAD. Density-functional theory was used to get insights into binding and band structure properties. The flat valence bands indicate a rather limited orbital overlap in Spiro(TFSI)2. QC 20200204
- Published
- 2020
24. Electron-hopping across dye-sensitized mesoporous NiO surfaces
- Author
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Sina Wrede, Lanlan He, Gerrit Boschloo, Leif Hammarström, Lars Kloo, and Haining Tian
- Subjects
Fysikalisk kemi ,General Physics and Astronomy ,Physical and Theoretical Chemistry ,Physical Chemistry - Abstract
To gain a deeper understanding of the underlying charge processes in dye sensitized photocathodes, lateral electron hopping across dye-sensitized NiO photocathodes was investigated. For dye-sensitized systems, hole hopping across photoanodes has been studied extensively in the literature but no expansive studies on electron hopping in sensitized photocathodes exist today. Therefore, an organic p-type dye (TIP) with donor–linker–acceptor design, showing high stability and electrochemical reversibility, was used to study the electron transfer dynamics (electron-hopping) between dyes with temperature dependent spectroelectrochemistry and computational simulations. Besides intermolecular electron-hopping across the surface with a rate constant in the order of 105 s−1, our results show a second electron hopping pathway between NiO surface states with a rate constant in the order of 107 s−1, which precedes the electron hopping between the dyes. Upon application of a potential step negative enough to reduce both the dye and NiO surface states, the majority of NiO surface states need to be reduced before intermolecular electron transfer can take place. The results indicate that, in contrast to sensitized photoanodes where intermolecular charge transfer is known to influence recombination kinetics, intermolecular charge transport processes in TIP dye sensitized NiO photocathodes is less relevant because the fast electron transport between NiO surface states likely dominates recombination kinetics.
- Published
- 2022
25. Inkjet-Printed Electron Transport Layers for Perovskite Solar Cells
- Author
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Belova, Dongli Lu, Wei Zhang, Lars Kloo, and Liubov
- Subjects
inkjet printing ,electron transport layers ,perovskite solar cells ,TiO2 ,SrTiO3 ,SnO2 ,cosolvent system - Abstract
Inkjet printing emerged as an alternative deposition method to spin coating in the field of perovskite solar cells (PSCs) with the potential of scalable, low-cost, and no-waste manufacturing. In this study, the materials TiO2, SrTiO3, and SnO2 were inkjet-printed as electron transport layers (ETLs), and the PSC performance based on these ETLs was optimized by adjusting the ink preparation methods and printing processes. For the mesoporous ETLs inkjet-printed from TiO2 and SrTiO3 nanoparticle inks, the selection of solvents for dispersing nanoparticles was found to be important and a cosolvent system is beneficial for the film formation. Meanwhile, to overcome the low current density and severe hysteresis in SrTiO3-based devices, mixed mesoporous SrTiO3/TiO2 ETLs were also investigated. In addition, inkjet-printed SnO2 thin films were fabricated by using a cosolvent system and the effect of the SnO2 ink concentrations on the device performance was investigated. In comparison with PSCs based on TiO2 and SrTiO3 ETLs, the SnO2-based devices offer an optimal power conversion efficiency (PCE) of 17.37% in combination with a low hysteresis. This work expands the range of suitable ETL materials for inkjet-printed PSCs and promotes the commercial applications of inkjet printing techniques in PSC manufacturing.
- Published
- 2021
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26. Inkjet-Printed Electron Transport Layers for Perovskite Solar Cells
- Author
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Dongli Lu, Wei Zhang, Lars Kloo, and Liubov Belova
- Subjects
Technology ,Microscopy ,QC120-168.85 ,inkjet printing ,cosolvent system ,QH201-278.5 ,SrTiO3 ,electron transport layers ,Engineering (General). Civil engineering (General) ,perovskite solar cells ,Article ,TK1-9971 ,Descriptive and experimental mechanics ,SnO2 ,TiO2 ,Electrical engineering. Electronics. Nuclear engineering ,TA1-2040 - Abstract
Inkjet printing emerged as an alternative deposition method to spin coating in the field of perovskite solar cells (PSCs) with the potential of scalable, low-cost, and no-waste manufacturing. In this study, the materials TiO2, SrTiO3, and SnO2 were inkjet-printed as electron transport layers (ETLs), and the PSC performance based on these ETLs was optimized by adjusting the ink preparation methods and printing processes. For the mesoporous ETLs inkjet-printed from TiO2 and SrTiO3 nanoparticle inks, the selection of solvents for dispersing nanoparticles was found to be important and a cosolvent system is beneficial for the film formation. Meanwhile, to overcome the low current density and severe hysteresis in SrTiO3-based devices, mixed mesoporous SrTiO3/TiO2 ETLs were also investigated. In addition, inkjet-printed SnO2 thin films were fabricated by using a cosolvent system and the effect of the SnO2 ink concentrations on the device performance was investigated. In comparison with PSCs based on TiO2 and SrTiO3 ETLs, the SnO2-based devices offer an optimal power conversion efficiency (PCE) of 17.37% in combination with a low hysteresis. This work expands the range of suitable ETL materials for inkjet-printed PSCs and promotes the commercial applications of inkjet printing techniques in PSC manufacturing.
- Published
- 2021
27. The dynamics of light-induced interfacial charge transfer of different dyes in dye-sensitized solar cells studied by
- Author
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Lanlan, He, Yu, Guo, and Lars, Kloo
- Abstract
The charge-transport dynamics at the dye-TiO
- Published
- 2021
28. Influence of TiO
- Author
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Altaf A, Shamsaldeen, Lars, Kloo, Yanting, Yin, Christopher, Gibson, Sunita Gautam, Adhikari, and Gunther G, Andersson
- Abstract
Surface defects influence the dye adsorption on TiO
- Published
- 2021
29. Effect of the Ancillary Ligand on the Performance of Heteroleptic Cu(I) Diimine Complexes as Dyes in Dye-Sensitized Solar Cells
- Author
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Daniele Franchi, Valentina Leandri, Angela Raffaella Pia Pizzichetti, Bo Xu, Yan Hao, Wei Zhang, Tamara Sloboda, Sebastian Svanström, Ute B. Cappel, Lars Kloo, Licheng Sun, and James M. Gardner
- Subjects
copper photosensitizers ,heteroleptic complexes ,Energy Engineering and Power Technology ,Materialkemi ,hard X-ray photoelectron spectroscopy ,diimine copper(I) complexes ,push-pull ,Electrochemistry ,Materials Chemistry ,Chemical Engineering (miscellaneous) ,in situ assembling ,DSSC ,Electrical and Electronic Engineering ,density functional theory calculation - Abstract
A series of heteroleptic Cu(I) diimine complexes with different ancillary ligands and 6,6'-dimethyl-2,2'-bipyridine-4,4'-dibenzoic acid (dbda) as the anchoring ligand were selfassembled on TiO2 surfaces and used as dyes for dye-sensitized solar cells (DSSCs). The binding to the TiO2 surface was studied by hard X-ray photoelectron spectroscopy for a brominecontaining complex, confirming the complex formation. The performance of all complexes was assessed and rationalized on the basis of their respective ancillary ligand. The DSSC photocurrent-voltage characteristics, incident photon-to-current conversion efficiency (IPCE) spectra, and calculated lowest unoccupied molecular orbital (LUMO) distributions collectively show a push-pull structural dye design, in which the ancillary ligand exhibits an electron-donating effect that can lead to improved solar cell performance. By analyzing the optical properties of the dyes and their solar cell performance, we can conclude that the presence of ancillary ligands with bulky substituents protects the Cu(I) metal center from solvent coordination constituting a critical factor in the design of efficient Cu(I)-based dyes. Moreover, we have identified some components in the I-/I-3(-)-based electrolyte that causes dissociation of the ancillary ligand, i.e., TiO2 photoelectrode bleaching. Finally, the detailed studies on one of the dyes revealed an electrolyte-dye interaction, leading to a dramatic change of the dye properties when adsorbed on the TiO2 surface.
- Published
- 2021
30. Exploring Overall Photoelectric Applications by Organic Materials Containing Symmetric Donor Isomers
- Author
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Xunfan Liao, Lin Zhang, Yiwang Chen, Licheng Sun, Zhaoyang Yao, Lars Kloo, Yu Guo, Fuguo Zhang, Heng Zhao, Zonglong Zhu, Wei Ma, and Yaxiao Guo
- Subjects
Chemical substance ,Materials science ,integumentary system ,genetic structures ,General Chemical Engineering ,food and beverages ,02 engineering and technology ,General Chemistry ,Photoelectric effect ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Combinatorial chemistry ,0104 chemical sciences ,Materials Chemistry ,sense organs ,0210 nano-technology - Abstract
Organic thin-film solar cells have demonstrated a bright prospect for commercial applications, where organic photosensitizers act as the most important kernel. In the global motif of sustainable de...
- Published
- 2019
31. An Indacenodithieno[3,2‐b]thiophene‐Based Organic Dye for Solid‐State p‐Type Dye‐Sensitized Solar Cells
- Author
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Lei Tian, Palas Baran Pati, Yiying Wu, Lars Kloo, Haining Tian, Sina Wrede, Allison Curtze, and Bo Xu
- Subjects
integumentary system ,Chemistry ,General Chemical Engineering ,Solid-state ,food and beverages ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Dye-sensitized solar cell ,chemistry.chemical_compound ,General Energy ,Energy materials ,Organic dye ,Thiophene ,Environmental Chemistry ,Moiety ,General Materials Science ,0210 nano-technology ,Linker - Abstract
An indacenodithieno[3,2-b]thiophene (IDTT) unit is used as a linker moiety to design a new p-type dye-TIP-for solid-state p-type dye-sensitized solar cells. Solar cells based on the TIP dye offered an efficiency of 0.18 % with an open-circuit photovoltage of 550 mV and a short-circuit photocurrent density of 0.86 mA cm
- Published
- 2019
32. Light-induced electrolyte improvement in cobalt tris(bipyridine)-mediated dye-sensitized solar cells
- Author
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István Furó, Valentina Leandri, Jiajia Gao, Ahmed M. El-Zohry, Yuan Fang, Govind Kumar Prajapati, Torben Lund, Jing Dai, Yan Hao, Wenxing Yang, Per H. Svensson, Gerrit Boschloo, and Lars Kloo
- Subjects
Photo-voltage ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,Conductivity ,Dye-sensitized solar cells ,Photochemistry ,Electrochemistry ,Redox ,Electrolytes ,Bipyridine ,chemistry.chemical_compound ,Charge transfer ,Redox systems ,Naturvetenskap ,General Materials Science ,Redox reactions ,Electrode/electrolyte interfaces ,Light effects ,Photocurrent ,Photoelectrochemical system ,Spectroscopic investigations ,Economic and social effects ,Renewable Energy, Sustainability and the Environment ,Light exposure ,Cobalt ,General Chemistry ,021001 nanoscience & nanotechnology ,Control experiments ,Dye-sensitized solar cell ,chemistry ,Natural Sciences ,0210 nano-technology - Abstract
Lithium-ion-free tris(2,2′-bipyridine) Co(ii/iii)-mediated electrolytes have previously been proposed for long-term stable dye-sensitized solar cells (DSSCs). Such redox systems also offer an impressive DSSC performance improvement under light soaking exposure, manifested by an increase in photocurrent and fill factor without the expense of decreasing photovoltage. Kinetic studies show that charge transfer and ion diffusion at the electrode/electrolyte interface are improved due to the light exposure. Control experiments reveal that the light effect is unambiguously associated with electrolyte components, [Co(bpy)3]3+ and the Lewis-base additive tert-butylpyridine (TBP). Electrochemical and spectroscopic investigation of the [Co(bpy)3]3+/TBP mixtures points out that the presence of TBP, which retards the electrolyte diffusion, however causes an irreversible redox reaction of [Co(bpy)3]3+ upon light exposure that improves the overall conductivity. This discovery not only provides a new strategy to mitigate the typical Jsc-Voc trade-off in Co(ii/iii)-mediated DSSCs but also highlights the importance of investigating the photochemistry of a photoelectrochemical system. Funding details: China Scholarship Council, CSC; Funding details: Energimyndigheten; Funding details: Vetenskapsrådet, VR; Funding text 1: We gratefully acknowledge the Swedish Research Council, the Swedish Energy Agency as well as the China Scholarship Council (CSC) for nancial support. The authors also thank Dr Lei Wang for his helpful assistance in 1H-NMR spectroscopic studies.
- Published
- 2019
33. Restructuring of Dye Layers in Dye Sensitized Solar Cells: Cooperative Adsorption of N719 and Chenodeoxycholic Acid on Titania
- Author
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Lars Kloo, Cameron J. Shearer, Gunther G. Andersson, Herri Trilaksana, Trilaksana, Herri, Shearer, Cameron, Kloo, Lars, and Andersson, Gunther G
- Subjects
co-adsorbent ,multilayer ,Chemistry ,Energy Engineering and Power Technology ,02 engineering and technology ,concentration depth profiles ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Ion ,neutral impact collision ion scattering spectroscopy ,dye sensitized solar cells ,Dye-sensitized solar cell ,chemistry.chemical_compound ,Adsorption ,monolayer ,Chenodeoxycholic acid ,Monolayer ,Materials Chemistry ,Electrochemistry ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering ,0210 nano-technology - Abstract
The effect of the co-adsorbent chenodeoxycholic acid (CDCA) up to a concentration of 20 mM on the adsorption of the dye N719 onto titania has been investigated using neutral impact collision ion scattering spectroscopy. It is shown that the co-adsorption of CDCA changes the adsorption mode of N719 from multilayer toward monolayer. FT-IR spectroscopy shows that the adsorption of CDCA increases with increasing CDCA concentration. In contrast, the amount of N719 adsorbed onto titania shows a minimum at 10 mM CDCA, and the relationship between the amount of CDCA and of N719 adsorbed onto titania depends nonmonotonically on the CDCA concentration. The co-adsorption of CDCA and N719 can be described as cooperative. The effect is observed for both low and high N719 concentrations. Refereed/Peer-reviewed
- Published
- 2018
34. Polyiodide Hybrid Perovskites: A Strategy To Convert Intrinsic 2D Systems into 3D Photovoltaic Materials
- Author
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Per H. Svensson, Lars Kloo, and Allan Starkholm
- Subjects
Materials science ,Photovoltaic system ,Energy Engineering and Power Technology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Polyiodide ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Organic inorganic ,Materials Chemistry ,Electrochemistry ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering ,0210 nano-technology ,Perovskite (structure) - Abstract
Two new organic inorganic hybrid perovskite compounds, (Me3S)(2)Pb5I14*2I(2) (1) and (C8H11S)(2)Pb2I6*I-2 (2), have been synthesized and subsequently characterized in this study. The materials were ...
- Published
- 2018
35. A facile route to grain morphology controllable perovskite thin films towards highly efficient perovskite solar cells
- Author
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Yuanyuan Li, Linqin Wang, Jerker Widengren, Lars Kloo, Haichun Liu, Zhaoyang Yao, Fuguo Zhang, James M. Gardner, Bin Cai, Licheng Sun, Jiayan Cong, Alireza Hajian, Jan Bergstrand, Xichuan Yang, Yan Hao, and Hans Ågren
- Subjects
Morphology (linguistics) ,Materials science ,Renewable Energy, Sustainability and the Environment ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,General Materials Science ,Electrical and Electronic Engineering ,Thin film ,0210 nano-technology ,Perovskite (structure) - Abstract
Perovskite photovoltaics have recently attracted extensive attention due to their unprecedented high power conversion efficiencies (PCEs) in combination with primitive manufacturing conditions. How ...
- Published
- 2018
36. Correction to 'Implicit Tandem Organic–Inorganic Hybrid Perovskite Solar Cells Based on Internal Dye Sensitization: Robotized Screening, Synthesis, Device Implementation, and Theoretical Insights'
- Author
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Allan Starkholm, Lars Kloo, and Per H. Svensson
- Subjects
Colloid and Surface Chemistry ,General Chemistry ,Biochemistry ,Catalysis - Published
- 2022
37. Efficient Naphthalene Imide-Based Interface Engineering Materials for Enhancing Perovskite Photovoltaic Performance and Stability
- Author
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Wai Yeung Wong, Yu Guo, Lars Kloo, Lanlan He, Junle Qu, Helin Wang, Jun Song, and Peng Cheng Qian
- Subjects
Materials science ,Passivation ,business.industry ,Photovoltaic system ,Perovskite solar cell ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Optoelectronics ,General Materials Science ,Surface charge ,Triiodide ,0210 nano-technology ,Imide ,business ,Layer (electronics) ,Perovskite (structure) - Abstract
The ways to overcome surface charge recombination and poor interface contact are still the central challenges for the development of inorganic-organic hybrid halide perovskite solar cells (PSCs). [6,6]-Phenyl C61 butyric acid methyl ester (PCBM) is commonly employed in PSCs, but it has some disadvantages including high charge recombination and poor surface coverage. Therefore, the addition of an interfacial engineering layer showing efficient surface passivation, electron extraction, and excellent interface contact can solve the above problems. Furthermore, by employing interface engineering with a spike structure of the energy levels, the reduced energy losses are beneficial to elevating the open-circuit voltage (Voc) in PSCs. Herein, the linear naphthalene imide dimer containing an indacenodithiophene unit (IDTT2NPI) has been developed as an excellent interface engineering material to strengthen the perovskite performance. The introduction of a spike interface on the top of a methylammonium lead triiodide (MAPbI3) film resulted in a high Voc of 1.12 V with the optimal efficiency reaching 20.2%. The efficiency enhancement can be traced to the efficient surface passivation and enhanced interface contact. The mechanism of IDTT2NPI as the interface engineering layer was investigated by both experiments and theoretical calculations. This work provides a promising naphthalene imide-based interfacial material for high-efficiency and stable PSCs.
- Published
- 2020
38. Conformational and Compositional Tuning of Phenanthrocarbazole-Based Dopant-Free Hole-Transport Polymers Boosting the Performance of Perovskite Solar Cells
- Author
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Yu Guo, Heng Wu, Yuanyuan Li, Zhaoyang Yao, Chinmaya Venugopal Srambickal, Dianyi Liu, Bin Cai, Zhou Liu, Fuguo Zhang, Gang Chen, Calvin J. Brett, Lanlan He, Jerker Widengren, Licheng Sun, Lars Kloo, Yaxiao Guo, Xichuan Yang, and James M. Gardner
- Subjects
chemistry.chemical_classification ,Dopant ,Energy conversion efficiency ,Stacking ,Rational design ,General Chemistry ,Polymer ,Conjugated system ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,Article ,0104 chemical sciences ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Chemical engineering ,ddc:540 ,Thiophene ,Perovskite (structure) - Abstract
Journal of the American Chemical Society 142(41), 17681 - 17692 (2020). doi:10.1021/jacs.0c08352, Conjugated polymers are regarded as promising candidates for dopant-free hole-transport materials (HTMs) in efficient and stable perovskite solar cells (PSCs). Thus far, the vast majority of polymeric HTMs feature structurally complicated benzo[1,2-b:4,5-b’]dithiophene (BDT) analogs and electron-withdrawing heterocycles, forming a strong donor–acceptor (D–A) structure. Herein, a new class of phenanthrocarbazole (PC)-based polymeric HTMs (PC1, PC2, and PC3) has been synthesized by inserting a PC unit into a polymeric thiophene or selenophene chain with the aim of enhancing the $π–π$ stacking of adjacent polymer chains and also to efficiently interact with the perovskite surface through the broad and planar conjugated backbone of the PC. Suitable energy levels, excellent thermostability, and humidity resistivity together with remarkable photoelectric properties are obtained via meticulously tuning the conformation and elemental composition of the polymers. As a result, PSCs containing PC3 as dopant-free HTM show a stabilized power conversion efficiency (PCE) of 20.8% and significantly enhanced longevity, rendering one of the best types of PSCs based on dopant-free HTMs. Subsequent experimental and theoretical studies reveal that the planar conformation of the polymers contributes to an ordered and face-on stacking of the polymer chains. Furthermore, introduction of the “Lewis soft” selenium atom can passivate surface trap sites of perovskite films by Pb–Se interaction and facilitate the interfacial charge separation significantly. This work reveals the guiding principles for rational design of dopant-free polymeric HTMs and also inspires rational exploration of small molecular HTMs., Published by American Chemical Society, Washington, DC
- Published
- 2020
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39. Molecular engineering of ionic type perylenediimide dimer-based electron transport materials for efficient planar perovskite solar cells
- Author
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Licheng Sun, Cheng Chen, Peng Liu, Huaming Li, Fen Qiao, Ming Cheng, Hongping Li, and Lars Kloo
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,Materials Science (miscellaneous) ,Photovoltaic system ,Energy conversion efficiency ,Energy Engineering and Power Technology ,Ionic bonding ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electron transport chain ,0104 chemical sciences ,Ion ,Molecular engineering ,Electron transfer ,Fuel Technology ,Nuclear Energy and Engineering ,Chemical engineering ,0210 nano-technology ,Perovskite (structure) - Abstract
The main of this work is to overcome the drawbacks of the traditional fullerene derivatives used as electron transport materials (ETMs) for perovskite solar cells (PSCs). Herein, a new strategy to design non-fullerene ETMs is presented by molecular engineering to include charged moieties in the ETM. The designed ETM FA2+-PDI2 is intrinsically ionic and the incorporated counter ions in FA2+-PDI2 significantly increase the electron conductivity and improve the film formation properties. Through careful device optimization, PSCs based on the ionic ETM FA2+-PDI2 exhibit an impressive average power conversion efficiency (PCE) of 17.0%, which is comparable to the PSC based on PC61 BM (17.5%). The superior photovoltaic performance can be attributed to efficient electron extraction and effective electron transfer in the PSCs. This work provides important insights regarding the future design of new and efficient non-fullerene ETMs for PSCs.
- Published
- 2018
40. Polymeric, Cost-Effective, Dopant-Free Hole Transport Materials for Efficient and Stable Perovskite Solar Cells
- Author
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Jerker Widengren, Yuanyuan Li, Jan Bergstrand, Xichuan Yang, Alireza Hajian, Fuguo Zhang, Yaxiao Guo, Yu Guo, Calvin J. Brett, Stephan V. Roth, Zhaoyang Yao, Bin Cai, Licheng Sun, James M. Gardner, and Lars Kloo
- Subjects
chemistry.chemical_classification ,Chemical substance ,Dopant ,Energy conversion efficiency ,Nanotechnology ,General Chemistry ,Polymer ,Photoelectric effect ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Colloid and Surface Chemistry ,chemistry ,Electrical resistivity and conductivity ,Science, technology and society ,Perovskite (structure) - Abstract
Perovskite solar cells (PSCs) has skyrocketed in the past decade to an unprecedented level due to their outstanding photoelectric properties and facile processability. However, the utilization of expensive hole transport materials (HTMs) and the inevitable instability instigated by the deliquescent dopants represent major concerns hindering further commercialization. Here, a series of low-cost, conjugated polymers are designed and applied as dopant-free HTMs in PSCs, featuring tuned energy levels, good temperature and humidity resistivity, and excellent photoelectric properties. Further studies highlight the critical and multifaceted roles of the polymers with respect to facilitating charge separation, passivating the surface trap sites of perovskite materials, and guaranteeing long-term stability of the devices. A stabilized power conversion efficiency (PCE) of 20.3% and remarkably enhanced device longevity are achieved using the dopant-free polymer P3 with a low concentration of 5 mg/mL, qualifying the device as one of the best PSC systems constructed on the basis of dopant-free HTMs so far. In addition, the flexible PSCs based on P3 also exhibit a PCE of 16.2%. This work demonstrates a promising route toward commercially viable, stable, and efficient PSCs.
- Published
- 2019
41. Electronic Structure of Two-Dimensional Lead(II) Iodide Perovskites: An Experimental and Theoretical Study
- Author
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Meysam Pazoki, Bertrand Philippe, Peng Liu, Majid Safdari, Håkan Rensmo, Olof Karis, James M. Gardner, Tomas Edvinsson, Dibya Phuyal, Lars Kloo, Sergei M. Butorin, and Kristina O. Kvashnina
- Subjects
Flexibility (engineering) ,Materials science ,General Chemical Engineering ,02 engineering and technology ,General Chemistry ,Electronic structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical physics ,Materials Chemistry ,Lead(II) iodide ,Chemical stability ,Hop (telecommunications) ,0210 nano-technology - Abstract
Layered two-dimensional (2D) hybrid organic-inorganic perovskites (HOP) are promising materials for light-harvesting applications because of their chemical stability, wide flexibility in compositio ...
- Published
- 2018
42. Efficient Dye-Sensitized Solar Cells with Voltages Exceeding 1 V through Exploring Tris(4-alkoxyphenyl)amine Mediators in Combination with the Tris(bipyridine) Cobalt Redox System
- Author
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Gerrit Boschloo, Martin Karlsson, Lars Kloo, Wenxing Yang, Jiayan Cong, Bo Xu, Xing Li, Jianli Hua, Yan Hao, and Shihuai Wang
- Subjects
inorganic chemicals ,Tris ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Redox ,0104 chemical sciences ,chemistry.chemical_compound ,Electron transfer ,Bipyridine ,Dye-sensitized solar cell ,Fuel Technology ,Chemistry (miscellaneous) ,Materials Chemistry ,Amine gas treating ,0210 nano-technology ,Cobalt - Abstract
Tandem redox electrolytes, prepared by the addition of a tris(p-anisyl)amine mediator into classic tris(bipyridine)cobalt-based electrolytes, demonstrate favorable electron transfer and reduced energy loss in dye-sensitized solar cells. Here, we have successfully explored three tris(4-alkoxyphenyl)amine mediators with bulky molecular structures and generated more effective tandem redox systems. This series of tandem redox electrolytes rendered solar cells with very high photovoltages exceeding 1 V, which approaches the theoretical voltage limit of tris(bipyridine)cobalt-based electrolytes. Solar cells with power conversion efficiencies of 9.7–11.0% under 1 sun illumination were manufactured. This corresponds to an efficiency improvement of up to 50% as compared to solar cells based on pure tris(bipyridine)cobalt-based electrolytes. The photovoltage increases with increasing steric effects of the tris(4-alkoxyphenyl)amine mediators, which is attributed to a retarded recombination kinetics. These results hi...
- Published
- 2018
43. Carrier Dynamics of Dye Sensitized-TiO2 in Contact with Different Cobalt Complexes in the Presence of Tri(p-anisyl)amine Intermediates
- Author
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Wenxing Yang, Lars Kloo, Gerrit Boschloo, and Yan Hao
- Subjects
Kinetics ,Wide-bandgap semiconductor ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Triphenylamine ,Photochemistry ,01 natural sciences ,Redox ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,chemistry ,Amine gas treating ,Physical and Theoretical Chemistry ,0210 nano-technology ,Cobalt ,Recombination - Abstract
Heterogeneous charge transfer processes at sensitized wide bandgap semiconductor surfaces are imperative for both fundamental knowledge and technical applications. Herein, we focus on the investigation of carrier dynamics of a triphenylamine-based dye, LEG4, sensitized TiO2 (LEG4/TiO2) in contact with two types of electrolyte systems: pure cobalt-based electrolytes and in combination with an organic donor, tri(p-anisyl)amine (TPAA). Four different cobalt redox systems with potentials spanning a 0.3 V range were studied, and the carrier recombination and regeneration kinetics were monitored both at low and at high TiO2 (e–) densities (1.3 × 1018 and 1.3 × 1019 cm–3, respectively). The results reveal that the introduction of the TPAA intermediate more effectively suppress the recombination loss of TiO2 (e–) under high charge conditions, close to open-circuit, as compared to low charge conditions. As a result, the charge transfer from the cobalt complexes to the oxidized dyes is significantly improved by the...
- Published
- 2018
44. D–A–D-Typed Hole Transport Materials for Efficient Perovskite Solar Cells: Tuning Photovoltaic Properties via the Acceptor Group
- Author
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Yong Hua, Licheng Sun, Peng Liu, Peng Xu, Yuanyuan Li, Bo Xu, and Lars Kloo
- Subjects
Solid-state chemistry ,Materials science ,business.industry ,Photovoltaic system ,Energy conversion efficiency ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Acceptor ,0104 chemical sciences ,Ambient air ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,Perovskite (structure) - Abstract
Two D-A-D-structured hole-transport materials (YN1 and YN2) have been synthesized and used in perovskite solar cells. The two HTMs have low-lying HOMO levels and impressive mobility. Perovskite-based solar cells (PSCs) fabricated with YN2 showed a power conversion efficiency (PCE) value of 19.27% in ambient air, which is significantly higher than that of Spiro-OMeTAD (17.80%). PSCs based on YN1 showed an inferior PCE of 16.03%. We found that the incorporation of the stronger electron-withdrawing group in the HTM YN2 improves the PCE of PSCs. Furthermore, the YN2-based PSCs exhibit good long-term stability retaining 91.3% of its initial efficiency, whereas PSCs based on Spiro-OMeTAD retained only 42.2% after 1000 h lifetime (dark conditions). These promising results can provide a new strategy for the design of D-A-D HTMs for PSC applications in future.
- Published
- 2018
45. Solid state p-type dye sensitized NiO–dye–TiO2 core–shell solar cells
- Author
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Lars Kloo, Zhibin Zhang, Palas Baran Pati, Lei Tian, Haining Tian, Jens Föhlinger, Junzhong Lin, Tomas Kubart, Gerrit Boschloo, Junliang Sun, Leif Hammarström, and Yong Hua
- Subjects
Materials science ,Non-blocking I/O ,Metals and Alloys ,Solid-state ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Barrier layer ,Core shell ,Chemical engineering ,Organic dye ,Materials Chemistry ,Ceramics and Composites ,0210 nano-technology - Abstract
Solid state p-type dye sensitized NiO-dye-TiO2 core-shell solar cells with an organic dye PB6 were successfully fabricated for the first time. With Al2O3 as an inner barrier layer, the recombinatio ...
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- 2018
46. Investigation of Triphenylamine (TPA)-Based Metal Complexes and Their Application in Perovskite Solar Cells
- Author
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Yan Hao, Yuanyuan Li, Biaobiao Zhang, Fuguo Zhang, Lars Kloo, Yong Hua, Azar Sadollahkhani, Wei Zhang, Majid Safdari, and Peng Liu
- Subjects
Materials science ,General Chemical Engineering ,02 engineering and technology ,General Chemistry ,Kemi ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Triphenylamine ,01 natural sciences ,Article ,0104 chemical sciences ,Metal ,lcsh:Chemistry ,chemistry.chemical_compound ,chemistry ,lcsh:QD1-999 ,visual_art ,Polymer chemistry ,Chemical Sciences ,visual_art.visual_art_medium ,0210 nano-technology ,Perovskite (structure) - Abstract
Triphenylamine-based metal complexes were designed and synthesized via coordination to Ni(II), Cu(II), and Zn(II) using their respective acetate salts as the starting materials. The resulting metal complexes exhibit more negative energy levels (vs vacuum) as compared to 2,2', 7,7'-tetrakis(N, N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD), high hole extraction efficiency, but low hole mobilities and conductivities. Application of dopants typically used for Spiro-OMeTAD was not successful, indicating a more complicated mechanism of partial oxidation besides the redox potential. However, utilization as hole-transport material was successful, giving a highest efficiency of 11.1% under AM 1.5G solar illumination.
- Published
- 2017
47. Polymer-Doped Molten Salt Mixtures as a New Concept for Electrolyte Systems in Dye-Sensitized Solar Cells
- Author
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Muthuraaman Bhagavathiachari, Viswanathan Elumalai, Jiajia Gao, and Lars Kloo
- Subjects
lcsh:Chemistry ,lcsh:QD1-999 ,Article - Abstract
A conceptually new polymer electrolyte for dye-sensitized solar cells is reported and investigated. The benefits of using this type of electrolyte based on ionic liquid mixtures (ILMs) and room temperature ionic liquids are highlighted. Impedance spectroscopy and transient electron measurements have been used to elucidate the background of the photovoltaic performance. Even though larger recombination losses were noted, the high ion mobility and conductivity induced in the ILMs by the added polymer result in enhanced overall conversion efficiencies.
- Published
- 2017
48. Tailor-Making Low-Cost Spiro[fluorene-9,9′-xanthene]-Based 3D Oligomers for Perovskite Solar Cells
- Author
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Erik M. J. Johansson, Yong Hua, Jinbao Zhang, Linqin Wang, Anders Hagfeldt, Yuanyuan Li, Gerrit Boschloo, Lars Kloo, Bo Xu, Alex K.-Y. Jen, Changqing Ruan, Licheng Sun, and Peng Liu
- Subjects
Xanthene ,Materials science ,General Chemical Engineering ,Biochemistry (medical) ,Perovskite solar cell ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Fluorene ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Environmental Chemistry ,0210 nano-technology ,Perovskite (structure) - Abstract
The power-conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have increased rapidly from about 4% to 22% during the past few years. One of the major challenges for further improvement ...
- Published
- 2017
49. Novel and Stable D–A−π–A Dyes for Efficient Solid-State Dye-Sensitized Solar Cells
- Author
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Peng Liu, Walid Sharmoukh, Bo Xu, Yuan Yuan Li, Gerrit Boschloo, Licheng Sun, and Lars Kloo
- Subjects
lcsh:Chemistry ,lcsh:QD1-999 ,General Chemical Engineering ,General Chemistry ,Article ,Addition/Correction - Abstract
Two novel organic donor–acceptor−π–acceptor sensitizers, W7 and W8, have been applied in efficient solid-state dye-sensitized solar cells (ssDSSCs). Using 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine) 9,9′-spirobifluorene (Spiro-OMeTAD) as hole-transport material (HTM), an excellent power conversion efficiency of 6.9% was recorded for W7, together with an excellent photocurrent of 10.51 mA cm–2 and a high open-circuit voltage of 880 mV under standard AM 1.5 G illumination (100 mW cm–2). The solid-state solar cells based on W8 showed an efficiency of 5.2%, with a good photocurrent of 9.55 mA cm–2 and an open-circuit voltage of 870 mV. Compared to that of the well-known WS2 sensitizer, the results show that the performance of the ssDSSC devices can be significantly improved by introducing triphenylamine moiety into their structure. In addition, results of photoinduced absorption spectroscopy show efficient dye regeneration for W7- and W8-based devices. A higher hole conductivity of the W7/HTM and W8/HTM layers compared to that of the WS2/HTM layer was observed, indicating an efficient charge transfer at the interfaces. The results obtained offer insights into the design of reliable and highly efficient ssDSSCs for large-scale applications.
- Published
- 2017
50. Study of Arylamine-Substituted Porphyrins as Hole-Transporting Materials in High-Performance Perovskite Solar Cells
- Author
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Beng S. Ong, Yong Hua, Xingzhu Wang, Yuanyuan Li, Wai-Kwok Wong, Peng Liu, Xunjin Zhu, Lars Kloo, and Song Chen
- Subjects
Electron mobility ,Materials science ,Inorganic chemistry ,Energy conversion efficiency ,Halide ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,Photochemistry ,01 natural sciences ,Porphyrin ,0104 chemical sciences ,Metal ,chemistry.chemical_compound ,chemistry ,visual_art ,visual_art.visual_art_medium ,General Materials Science ,0210 nano-technology ,Pyrrole ,Perovskite (structure) - Abstract
To develop new hole-transporting materials (HTMs) for efficient and stable perovskite solar cells (PSCs), 5,10,15,20-tetrakis{4-[N,N-di(4-methoxylphenyl)amino-phenyl]}-porphyrin was prepared in gram scale through the direct condensation of pyrrole and 4-[bis(4-methoxyphenyl)amino]benzaldehyde. Its Zn(II) and Cu(II) complexes exhibit excellent thermal and electrochemical stability, specifically a high hole mobility and very favorable energetics for hole extraction that render them a new class of HTMs in organometallic halide PSCs. As expected, ZnP as HTM in PSCs affords a competitive power conversion efficiency (PCE) of 17.78%, which is comparable to that of the most powerful HTM of Spiro-MeOTAD (18.59%) under the same working conditions. Meanwhile, the metal centers affect somewhat the photovoltaic performances that CuP as HTM produces a lower PCE of 15.36%. Notably, the PSCs employing ZnP show a much better stability than Spiro-OMeTAD. Moreover, the two porphyrin-based HTMs can be prepared from relatively cheap raw materials with a facile synthetic route. The results demonstrate that ZnP and CuP can be a new class of HTMs for efficient and stable PSCs. To the best of our knowledge, this is the best performance that porphyrin-based solar cells could show with PCE17%.
- Published
- 2017
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