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Developing potential hole transport materials (HTMs) is an effective approach to reduce carrier nonradiative recombination and improve the efficiency of perovskite solar cells (PSCs). To investigate the intermolecular and interfacial interactions of HTMs in PSC devices, two molecules (RQ7 and RQ8) with substituent group functionalization are designed by isomerizing ‐F and ‐SMe in the para‐ and ortho‐positions on the side chain of carbazole diphenylamine‐based HTMs. Theoretical simulations indicate that the functionalization of substituent groups in HTMs alters their dipole moments and electronic structures, as well as their intermolecular interactions, hole transport capabilities, and interfacial interactions at the HTMs/perovskite interface. Experimental results show that RQ8 exhibited higher hole mobility, better film‐forming ability, and reduced electron‐hole recombination, resulting in RQ8‐based PSC devices achieving a higher power conversion efficiency than those based on RQ7. Herein, it is demonstrated that isomerous functionalization of substituent groups in carbazole diphenylamine‐based HTMs is a feasible strategy for controlling and regulating the intermolecular and interfacial interactions of HTMs in PSC applications. [ABSTRACT FROM AUTHOR]

Introducing 2D perovskite onto the surface of 3D perovskite could not only passivate the defects in 3D perovskite, but also protect the 3D perovskite from humidity invasion, which could improve the device stability. The choice of spacer cations in 2D perovskites directly influences the overall properties of the 2D layer, which is crucial to the efficiency and stability of devices. Herein, trifluoromethyl benzylamine is developed as the 2D spacer cation, and the effects of –CF3 at different substitution positions on the surface morphology, carrier dynamics, and device performances are systematically investigated. Results show that the 3‐TFPMAI‐treated 2D/3D perovskite film shows smoother morphology, with fewer surface defects and less nonradiative recombination. Moreover, with a matched energy level, 3‐TFPMAI modification can accelerate hole extraction and hole transporting. The 3‐TFPMAI‐treated 2D/3D cell achieves a champion efficiency of 22.68%. What's more, the introduction of fluoride‐containing groups increases the hydrophobicity of the 2D layer, which effectively resists moisture erosion and greatly improves the long‐term and operational stability of the perovskite solar cells. [ABSTRACT FROM AUTHOR]

The uncoordinated lead cations are ubiquitous in perovskite films and severely affect the efficiency and stability of perovskite solar cells (PSCs). In this work, 15‐crown‐5 with various heteroatoms are connected to the organic semiconductor carbazole diphenylamine, and two new compounds, CDT‐S and CDT‐N, are developed to modify the Pb2+ defects in perovskite films through the anti‐solvent method. Apart from the oxygen atoms, there are also N atoms on crown ether ring in CDT‐N, and both S and N heteroatoms in CDT‐S. The heteroatoms enhance the interaction between the crown ether‐based semiconductors and the undercoordinated Pb2+ defect in perovskite. Particularly, the stronger interaction between S atoms and Pb2+ further enhances the defect passivation effect of CDT‐S than CDT‐N, thereby more effectively suppressing the non‐radiative recombination of charge carriers. Finally, the efficiency of the device treated with CDT‐S is up to 23.05 %. Moreover, the unencapsulated device based on CDT‐S maintained 90.5 % of the initial efficiency after being stored under dark conditions for 1000 hours, demonstrating good long‐term stability. Our work demonstrates that crown ethers are promising in perovskite solar cells, and the crown ether containing multiple heteroatoms could effectively improve both efficiency and stability of devices. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A series of unreported fullerodihydropyridine‐3‐ones were synthesized as a new family of fullerene derivatives in moderate to good yields by a simple one‐step reaction of [60]fullerene with cheap and readily available β‐substituted ethylamines in the absence or presence of arylacetaldehydes under the assistance of Cu(OAc)2. The in situ generation of arylacetaldehydes by the C—N bond cleavage of arylethylamines avoided their complex synthesis in advance and realized the preparation of fullerodihydropyridine‐3‐ones with structural and functional diversities, which may have promising applications in perovskite solar cells to improve the performance of photovoltaic devices due to the existence of a large π‐conjugated system on the dihydropyridine‐3‐one ring. [ABSTRACT FROM AUTHOR]

Hole transporting materials (HTMs) are imperative for promoting the development of perovskite solar cells (PSCs). Herein, three isomers of RQ4, RQ5, and RQ6 are constructed by methylthio (‐SMe) group in the para, meta, and adjacent sites of terminal benzene on the side‐chain of carbazole‐arylamine derivatives based HTMs, and investigated by means of the theoretical simulation and experimental characterization. As a result of the theoretical simulation, the isomeric HTMs of RQ4‐RQ6 exhibit appropriate highest occupied molecular orbital /lowest unoccupied molecular orbital energy levels and good optical properties. However, by comparison with RQ4 and RQ5, a better planar configuration and closer molecular stacking for RQ6 may be beneficial to promote the hole coupling, interface interaction, and charge transfer at perovskite/HTMs interface. In order to verify the accuracy of the theoretical model, the designed RQ4‐RQ6 are synthesized to be used to assemble PSCs devices. In comparison to isomers RQ4 (20.07%) and RQ5 (18.18%) based devices, the RQ6 based devices has higher power conversion efficiency of 21.03% because of its high hole mobility, the film formation ability, and large charge transfer at perovskite/HTMs interface. The experimental results confirm the reliability of the theoretical simulation and provide an effective strategy to obtain potential HTMs through isomerization of side‐chain functional groups. [ABSTRACT FROM AUTHOR]

In conventional (n‐i‐p) perovskite solar cells (PSCs), spiro‐OMeTAD is the most widely used hole‐transporting material (HTM), which contributes to the current state‐of‐the‐art efficiency. Suffering from the low conductivity, dopants such as LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) and tBP are usually required to achieve excellent hole transport properties in spiro‐OMeTAD. Nevertheless, the hygroscopicity and the migration of Li+ during device operation severely affect the device's stability. To address the aforementioned issue, a 12‐crown‐4‐based organic semiconductor (CDT) is synthesized and applied in PSCs. Notably, CDT is simultaneously doped in spiro‐OMeTAD and perovskite layer through the antisolvent method. In this way, the strong "host‐guest" interaction between crown ether and Li+ effectively inhibits its migration both in the hole transporting layer (HTL) and at the perovskite/HTM interface. Furthermore, the carbazole diphenylamine group in CDT facilitates hole transport, and meanwhile improves the hydrophobicity of the HTL. In addition, CDT added into the perovskite layer is also able to passivate defects by interacting with the undercoordinated Pb2+. In light of the aforementioned advantages, the CDT‐based device shows a high power conversion efficiency approaching 23%, with excellent long‐term stability. [ABSTRACT FROM AUTHOR]

The development of hole‐transporting materials (HTMs) that can passivate defects in perovskite is of great significance in improving the efficiency and long‐term stability of perovskite solar cells. To date, the investigation on HTMs mainly focus on exploring new structures, while molecular configuration is seldomly concerned. In this work, two small molecules are developed as HTMs with benzil and phenanthrene quinone as the core structure, respectively. With similar structure and the same defect passivation groups, whereas, the two molecules exhibit different configurations, thus distinct properties. Compared to 3,6‐bis(3,6‐bis(bis(4‐methoxyphenyl)amino)‐9H‐carbazol‐9‐yl)phenanthrene‐9,10‐dione (PQ) with a rigid core structure, the benzil group in 1,2‐bis(4‐(3,6‐bis(bis(4‐methoxyphenyl)amino)‐9H‐carbazol‐9‐yl)phenyl)ethane‐1,2‐dione (DB) is flexible and can adjust molecular configuration to efficiently interact with the underlying perovskite material, which is confirmed from both experimental results and theoretical simulations. The DB‐based device exhibits a high power conversion efficiency of 22.21% with excellent long‐term stability, superior to the PQ‐based device (20.22%). This study demonstrates that molecular configuration engineering will directly affect the properties of hole transport materials, as well as their interactions with perovskite, which should also be taken into consideration when devising HTMs. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The surface properties and chemical interactions are critical for perovskite solar cells (PVSCs). In this work, we show that the polypropylene glycol (PPG) can simultaneously passivate the NiOx surface and grain boundaries of perovskite films, allowing more efficient charge transfer at the anode interface and reducing the recombination of PVSCs. As a result, the open‐circuit voltage (Voc) of MAPbI3 based inverted PVSCs increases from 1.087 V to 1.127 V, and the short‐circuit current density (Jsc) is increased from 20.87 mA·cm–2 to 22.32 mA·cm–2, thereby realizing the improvement of the device power conversion efficiency (PCE) from 18.34% to 20.12%. Moreover, the steady‐state output of the PVSCs is remarkably improved by incorporating PPG. Further analysis of surface properties suggests that part of the PPG at the interface can permeate into the precursor solution with the help of DMF solvent and remain in the perovskite layer to form a concentration gradient. The ether bond of PPG and the uncoordinated Pb2+ in the perovskite are coordinated to achieve passivation effects and improve device performance. Our work provides a rational strategy for the preparation of high‐performance PVSCs. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The surface properties and chemical interactions are critical for perovskite solar cells (PVSCs). In this work, we show that the polypropylene glycol (PPG) can simultaneously passivate the NiOx surface and grain boundaries of perovskite films, allowing more efficient charge transfer at the anode interface and reducing the recombination of PVSCs. As a result, the open‐circuit voltage (Voc) of MAPbI3 based inverted PVSCs increases from 1.087 V to 1.127 V, and the short‐circuit current density (Jsc) is increased from 20.87 mA·cm–2 to 22.32 mA·cm–2, thereby realizing the improvement of the device power conversion efficiency (PCE) from 18.34% to 20.12%. Moreover, the steady‐state output of the PVSCs is remarkably improved by incorporating PPG. Further analysis of surface properties suggests that part of the PPG at the interface can permeate into the precursor solution with the help of DMF solvent and remain in the perovskite layer to form a concentration gradient. The ether bond of PPG and the uncoordinated Pb2+ in the perovskite are coordinated to achieve passivation effects and improve device performance. Our work provides a rational strategy for the preparation of high‐performance PVSCs. [ABSTRACT FROM AUTHOR]

As a state‐of‐the‐art n‐type material, PC61BM ((6,6)‐phenyl C61 butyric‐ methylester) has been largely used as the top electron transporting layer (ETL) in inverted perovskite solar cells (PSCs). Whereas so far, there have been few reports on using pristine PC61BM as the bottom ETL in conventional (n‐i‐p‐type) PSCs, because it will be partially dissolved by the perovskite precursor solution (such as N,N‐Dimethylformamide and Dimethyl sulfoxide). In this work, the successful application of pristine PC61BM as an annealing‐free ETL is reported for conventional PSCs, by ingeniously utilizing the "saturated solution" strategy. Specifically, the perovskite precursor solution is presaturated with PC61BM before deposition, in this way, not only the underlying PC61BM layer can be "reserved", the added PC61BM in perovskite is also able to passivate defects in perovskite grain boundaries, thus facilitating charge transporting and reducing charge recombination. Encouragingly, the PC61BM ETL can avoid high‐temperature calcination or thermal annealing, thus greatly simplifying the manufacturing processes and reducing production costs. The CH3NH3PbI3–xClx‐based champion device shows the highest efficiency of 20.85% with high reproducibility. The strategy is simple, straightforward, and cost‐effective, when compared to most of the present reported ways for depositing ETLs. [ABSTRACT FROM AUTHOR]

Hole‐transporting materials (HTMs) are the key component of perovskite solar cells (PSCs) for the role of extracting photogenerated holes, as well as the charge transporting between perovskite layer and metal electrode. Herein, with the aim to enhance the hole mobility by compact molecular packing, the modification of HTMs focuses on the extension of conjugated cores from the commonly used carbazole (Cz) to tetrabenzo[a,c,g,i]carbazole (TBC). Because of the closely cofacial stacking mode of the TBC core with an X‐type symmetric structure, the resultant TBC‐2,7,11,16‐tetra‐diphenylamine (TD) can achieve a hole mobility of 6.6 × 10−4 cm2 V−1 s−1 and the corresponding conversion efficiency of 20.52%, higher than that of the analogue Cz‐TD (18.34%). [ABSTRACT FROM AUTHOR]

Lead‐based organic–inorganic hybrid perovskite solar cells (PSCs) usually show an absorption edge around 800 nm, while the near‐infrared (NIR) wavelength beyond 800 nm cannot be utilized. Herein, a new indacenothiophene‐based electron transporting material (ETM), namely, ITCP‐M, is developed, which works to enhance electron extraction and electron transporting, and simultaneously extends photoresponses to the NIR region in MAPbI3‐based inverted PSCs. Notably, the ITCP‐M‐based device exhibits a prominent photoresponse beyond 800 nm as observed from the external quantum efficiency (EQE) spectra, contributing to enhanced short‐circuit current density (Jsc) without sacrificing the open‐circuit voltage and fill factor. As a result, inverted PSCs using ITCP‐M ETM delivers a high efficiency of 19.15%, representing one of the highest efficiencies in inverted PSCs using nonfullerene ETMs. This work provides a new and simple strategy to extend photoresponses to the NIR absorption region for MAPbI3‐based inverted PSCs that can significantly improve device performance. [ABSTRACT FROM AUTHOR]

Electron transport materials (ETM) play an important role in the improvement of efficiency and stability for inverted perovskite solar cells (PSCs). This work reports an efficient ETM, named PDI‐C60, by the combination of perylene diimide (PDI) and fullerene. Compared to the traditional PCBM, this strategy endows PDI‐C60 with slightly shallower energy level and higher electron mobility. As a result, the device based on PDI‐C60 as electron transport layer (ETL) achieves high power conversion efficiency (PCE) of 18.6 %, which is significantly higher than those of the control devices of PCBM (16.6 %) and PDI (13.8 %). The high PCE of the PDI‐C60‐based device can be attributed to the more matching energy level with the perovskite, more efficient charge extraction, transport, and reduced recombination rate. To the best of our knowledge, the PCE of 18.6 % is the highest value in the PSCs using PDI derivatives as ETLs. Moreover, the device with PDI‐C60 as ETL exhibits better device stability due to the stronger hydrophobic properties of PDI‐C60. The strategy using the PDI/fullerene hybrid provides insights for future molecular design of the efficient ETM for the inverted PSCs. [ABSTRACT FROM AUTHOR]

In this work, the thiadiazolopyridine (PT) unit was introduced as the core structure, with N3,N3,N6,N6‐tetrakis(4‐methoxyphenyl)‐9‐phenyl‐9 H‐carbazole‐3,6‐diamine as the peripheral group, to obtain a new compound, JY8, for use as a hole‐transport material (HTM) in planar perovskite solar cells (PSCs). Compared with the previously reported JY5 with benzothiadiazole as the core structure, the PT unit with stronger electron‐withdrawing ability enhanced the intermolecular dipole–dipole interaction. Moreover, the introduction of the PT unit made the central part in JY8 more planar than its analogue JY5, which is conducive to charge transport. Field‐emission (FE)‐SEM images suggested a smooth and condense morphology of the JY8 film, which could improve the contact between the perovskite layer and the metal electrode. Space‐charge limitation of current results, steady‐state, and time‐resolved photoluminescence decay curves indicated that JY8 as HTM facilitated hole extraction and hole transport. Consequently, planar PSCs fabricated with JY8 as the HTM exhibited a decent efficiency of 19.14 % with a high fill factor of 81 %. In the core: The thiadiazolopyridine unit is introduced as the core structure, with N3,N3,N6,N6‐tetrakis(4‐methoxyphenyl)‐9‐phenyl‐9 H‐carbazole‐3,6‐diamine as the peripheral group, to obtain a new compound, JY8, for use as a hole‐transport material in planar perovskite solar cells. [ABSTRACT FROM AUTHOR]

Highlights • Develop two-stage stochastic program to utilize flexibility of EV charging. • EV-charging flexibility is used to provide frequency regulation. • Employ sample-average approximation to efficiently solve model. • Demonstrate model and algorithm using Central-Ohio-based case study. • Provision of grid services generates immense value to incentivize EV adoption and charging-station deployment. Abstract The charging of battery electric vehicles (BEVs) is a potential source of flexibility and ancillary services to power systems. This paper proposes a two-stage stochastic problem that can be used to optimize the charging of BEVs in a public charging station to provide frequency regulation and energy arbitrage. The model also co-optimizes the use of distributed energy resources, including battery energy storage and photovoltaic solar panels. We demonstrate the performance of the proposed model using a case study based on the Central-Ohio region. The case study shows that proper management of flexibility in BEV charging can provide high-quality frequency regulation services, which is also of significant financial value to the station operator. As such, the modeling methodology that we propose here can further accelerate the adoption of BEVs. This is because the value streams generated by the provision of frequency regulation can reduce the cost of BEV ownership and the net cost of owning and operating a public BEV-charging station. [ABSTRACT FROM AUTHOR]

In this work, fullerene derivatives (ICBA and PCBM) are dissolved into perovskite precursors, and the corresponding perovskite solar cells are fabricated. Compared to PCBM, ICBA has better solubility in perovskite precursor solution (DMF). The added small amount of ICBA filled the vacancies at the grain boundaries of perovskite, and produced continuous pathways for electron extraction to enhance performance. Steady-state and time-resolved photoluminescence, together with the impedance measurements confirm the enhanced electron transporting property in perovskite-ICBA film. An excellent PCE of 18.14% is achieved in CH 3 NH 3 PbI 3- x Cl x -ICBA-based solar cells with significantly suppressed hysteresis. Poor solubility of PCBM leads to a low concentration of PCBM in perovskite precursor, and results in a moderate PCE of 16.54% in device containing Perovskite-PCBM. By contrast, device based on pristine perovskite shows an inferior efficiency of 15.49% with large hysteresis. PSCs prepared from perovskite-ICBA with large area (1.12 cm 2 ) are also fabricated, exhibiting a PCE of 13.69%. Results demonstrate that the strategy of dissolving ICBA into perovskite precursor directly is an efficient and facile way to improve PSCs performance as well as to reduce hysteresis. [ABSTRACT FROM AUTHOR]

Abstract: Upconversion glasses are capable of converting the sub‐bandgap NIR light into photons of a particular wavelength which can be efficiently utilized by solar cells. Herein, the Yb3+/Er3+ co‐doped fluorotellurite upconversion glasses were prepared. The most intense upconversion luminescence (UCL) under 980‐nm LD excitation was obtained in the glass with Yb3+‐to‐Er3+ molar ratio of 10:1. The dependences of UCL on the pump power and temperature were investigated. The UCL can be mainly attributed to the two‐photon involved energy transfer processes and is very stable to the change in temperature even when heated up to 200°C. The subsequent implementation of the glass as upconverter for a MAPbI3‐xClx‐based perovskite solar cell (PSC) resulted in an open circuit voltage of 0.83 V and a short circuit current density of 0.32 mA/cm2. This application of upconversion glass for enhancing the NIR light harvesting offers a promising way to improve the photo‐electric conversion efficiencies of PSCs. [ABSTRACT FROM AUTHOR]

Here, 2,2′- and 3,3′-bipyridine are introduced for the first time as the core structure to get two new hole transport materials (HTMs), namely F22 and F33. The electron-withdrawing nature of bipyridine lowers the HOMO level of the new compounds and enhances the open-circuit voltage of perovskite solar cells. Especially for F33, the better planarity leads to better conjugation in the whole molecule and the molecular interaction is enhanced. Hole-mobility tests, steady-state photoluminescence (PL) spectra as well as time-resolved PL decay results demonstrate that the new HTMs exhibit good hole extraction and hole-transporting property. Impressive power conversion efficiencies of 17.71 and 18.48 % are achieved in conventional planar perovskite (CH3NH3PbI3− xCl x) solar cells containing F22 and F33 as HTMs, respectively. As far as we know, this is the first report on bypiridine-based HTMs with leading efficiencies, and the design motif in this work opens a new way for devising HTMs in the future. [ABSTRACT FROM AUTHOR]

Fluorine-substituted benzothiadiazole (BT) was introduced as a core structure to construct new hole transport materials. Planar perovskite solar cells with conventional materials (CH3NH3PbI3−xClx) were fabricated. The perovskite solar cells using monofluorinated BT exhibit a leading efficiency of 18.54% with a FF as high as 81%. [ABSTRACT FROM AUTHOR]

Through molecular engineering, a benzothiadiazole unit is incorporated as the core structure to generate a new hole transport material JY5. Cyclic voltammetry measurement suggests matched energy level of JY5 with the perovskite materials. TGA and DSC show excellent thermal stability of JY5. Hole mobility and PL decay experiments indicate good hole transport ability in JY5. As a result, perovskite solar cells utilizing JY5 as HTM outperforms the biphenyl centered analogue, and a champion efficiency of 16.87% was achieved among the HTMs studied in this work, with short-circuit current ( J sc ) of 21.06 mA cm −2 , open-circuit voltage ( V oc ) of 1.06 V, and fill factor ( FF ) of 0.76. The high efficiency as well as low costs make it potential alternative to the highly cost Spiro-OMeTAD. [ABSTRACT FROM AUTHOR]

In this work, four tetraphenylethylene (TPE)-centered hole transport materials (HTMs), with 2,7- or 3,6-substituted carbazole derivatives as periphery groups are deliberately synthesized and characterized. Their photophysical properties, energy levels, and photovoltaic performances are systematically investigated, and their performances as HTMs are discussed with respect to the different substituent positions on the carbazole moiety. It is interesting to find that the TPE-based HTMs with 2,7-carbazole substituents rival the 3,6-carbazole substituents in hole mobility and hole extraction ability. A high power conversion efficiency of up to 16.74 % is achieved for the devices based on the 2,7-carbazole periphery arms, which is even higher than the one of the 'star' HTM Spiro-OMeTAD (2,2-7,7-tetrakis( N, N′-diparamethoxy-phenylamine 9,9′-spirobifluorene) under the same conditions. As far as we know, this is the highest efficiency achieved in tetraphenylethylene derivatives. [ABSTRACT FROM AUTHOR]

A N , N -dimethylamino substituted tetraphenylethylene derivative (TPE-NMe) was synthesized and characterized, and was successfully applied as hole transport material (HTM) in perovskite solar cells. The methoxy-substituted analogue TPE-4DPA was also studied for comparison. The effect of replacing the para -methoxy substituent with N , N -dimethylamino on photophysical properties, energy levels, and hole transport properties is investigated. Photovoltaic performances of the corresponding devices using the two HTMs are studied. Compared to the methoxy substituent, the N , N -dimethylamino groups in TPE-NMe generates a lower V oc (0.87 V), yet it provides higher J sc (21.69 mA/cm 2 ) and FF (0.73) values, resulting in an overall power conversion efficiency of 13.78%. [ABSTRACT FROM AUTHOR]

Three tetrapheynlethylene derivatives ( N, N-di(4-methoxyphenyl)aminophenyl-substituted tetraphenylethylene; TPE-4DPA) with different methoxy positions ( pp-, pm-, and po-) have been synthesized and characterized. The methoxy groups can control the oxidation potential of the materials, and the electronic properties of the derivatives were affected by the position of the methoxy substituents. These compounds were synthesized in a facile and cost-effective way, and were applied as hole-transport materials in perovskite solar cells. The corresponding cell performances were compared with respect to their structure modifications, and it was found that the derivative with m-OMe substituents showed the highest power conversion efficiency (PCE) of 15.4 %, with a Jsc value of 20.04 mA cm−2, a Voc value of 1.07 V, and a fill factor ( FF) value of 0.72, which is higher than the p-OMe and o-OMe substituents. Moreover, the PCE of pm-TPE-4DPA is comparable with that of the state-of-the-art 2,2′,7,7′-tetrakis( N, N′-di- p-methoxyphenylamine)-9,9′-spirobifluorene under identical conditions. [ABSTRACT FROM AUTHOR]

• A new bottom surface modification strategy is demonstrated by introducing zwitterionic polysquaraine into PTAA. • PASQ-IDT ameliorated the wettability of PTAA film and improved the perovskite film quality. • Promoted carrier extraction at the perovskite/HTL interface and reduced trap density were realized by modified HTL. • MAPbI 3-x Cl x -based inverted PSCs with the modified PTAA HTL showed efficiency exceeding 21 %. In inverted perovskite solar cells (PSCs), perovskite crystals grow on the bottom hole transporting layer (HTL), and the HTL not only functions to extract and transport holes, but also manipulates the perovskite crystallization process and affects perovskite film quality. Poly(triarylamine) (PTAA) represents one of the most widely used and highly-efficient hole transport material in inverted PSCs. However, strong hydrophobicity makes the PTAA layer incompatible to the polar perovskite precursor solution, consequently, solvent pre-wetting or introducing an amphiphilic interlayer is always applied to PTAA layer before depositing perovskite film. Herein, we develop an efficient approach of modifying the bottom interface of perovskite layer by blending PTAA with a p-type zwitterionic polysquaraine (PASQ-IDT). The zwitterionic PASQ-IDT not only significantly improves the wettability of PTAA film toward perovskite precursor, leading to large perovskite grains with uniform sizes, but also enables more efficient carrier extraction at the perovskite/HTL interface, accompanied with efficiently reduced trap densities at the bottom surface. As a result, MAPbI 3-x Cl x -based inverted PSCs utilizing the modified PTAA HTL show an impressive efficiency exceeding 21 %, which represents a high value for MA-based inverted PSCs. [ABSTRACT FROM AUTHOR]

Ternary blend solar cells have been intensively studied in recent years to harvest more photons over the near-IR region. In this work, the effects of adding a diketopyrrolopyrrole dye (py-DPP) into a conventional P3HT:PC 71 BM based bulk heterojunction photovoltaic cell are investigated. The near infrared absorption of the blend is enhanced by the doped py-DPP dye, leading to more than 20% increased power conversion efficiency compared to the P3HT:PC 71 BM binary system. The highest efficiency of 4.05% is achieved for a P3HT:PC 71 BM blend with 2.4 wt % of py-DPP. [ABSTRACT FROM AUTHOR]

Three new D-A-A-type organic sensitizers - W1, W2, and W3 - have been synthesized and applied for p-type dye-sensitized solar cells. For the first time, the electron-withdrawing 2,1,3-benzothiadiazole (BT) unit has been applied as the π-bridge between the triphenylamine donor and different acceptors in these dye molecules. It turns out that these dyes all exhibit power conversion efficiencies exceeding 0.1 %, and that the best performance is achieved by the dye W2, with an octyl 2-cyanoacrylate acceptor. It shows a power conversion efficiency of 0.166 %, with a short circuit current of 4.16 mA cm-2 and an open circuit voltage of 0.121 V. The higher light-harvesting efficiency leads to a higher photocurrent in W2. In addition, electrochemical impedance spectroscopy (EIS) studies suggest slower charge recombination at the metal oxide/electrolyte interface and a faster hole-transporting ability of W2. The factors together may account for the higher power conversion efficiency of W2. This work demonstrates rational design of these dye molecules for the construction of efficient p-type sensitizers. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A series of unreported fullerodihydropyridine‐3‐ones were synthesized as a new family of fullerene derivatives in moderate to good yields by a simple one‐step reaction of [60]fullerene with cheap and readily available β‐substituted ethylamines in the absence or presence of arylacetaldehydes under the assistance of Cu(OAc)2. The in situ generation of arylacetaldehydes by the C—N bond cleavage of arylethylamines avoided their complex synthesis in advance and realized the preparation of fullerodihydropyridine‐3‐ones with structural and functional diversities, which may have promising applications in perovskite solar cells to improve the performance of photovoltaic devices due to the existence of a large π‐conjugated system on the dihydropyridine‐3‐one ring. [ABSTRACT FROM AUTHOR]

Bridged triphenylamine having almost planar core structure is a potential donor moiety for DSSCs. In this work, three novel D-π-A organic dyes TB-1, TB-2, and TB-3, containing diarylmethylene-bridged triphenylamine as the donor moiety, cyanoacrylic acid as the acceptor, and thiophene, benzene or furan as the π-spacers were synthesized and characterized for applications in dye-sensitized solar cells (DSSCs). Their photophysical, electrochemical, and photovoltaic properties were investigated, the performance of the triphenylamine donor was compared, and the effect of different π-spacers was evaluated. Results demonstrated that compared to the nonplanar triphenylamine donor, the more planar bridged TPA could offer better charge transfer process and as a result higher performances. On the other hand, in these compounds, both thiophene and furan linkages show better planarization and electron delocalization compared to the benzene linkage in this molecular system. Accordingly, dye TB-1 and TB-3 show higher IPCE and J sc values. Considering the larger V oc of dye TB-3, therefore it outperforms the other two sensitizers, exhibiting power conversion efficiency of 3.81%, with J sc of 7.54 mA cm −2 and V oc of 725 mV under simulated AM 1.5 irradiation (100 mW cm −2 ). The results are further confirmed by the EIS experiments. [ABSTRACT FROM AUTHOR]

Two donor-acceptor copolymers (P1 and P2) containing isoindigo as the acceptor unit and the benzodithiophene and bisthiophene-dithieno[3,2-b:2′,3′-d]-pyrrole as the donor unit have been designed and synthesized by the Pd-catalyzed Stille coupling reaction. The copolymers show broad and flat absorption, exhibit good solubility, and thermal stability, but possess optical bandgaps of 1.62 and 1.42 eV, respectively, and different donor-acceptor distance, of which the former is shorter than the later. The power conversion efficiency of the polymer solar cells based on P2:PC61BM (1:1 wt%) reached 1.86% with open-circuit voltage of 0.54 V and a short-circuit current of 6.36 mA/cm2, under the illumination of AM 1.5, 100 mW/cm2. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

High-performance hole-transporting materials (HTMs) play an essential role in improving efficiency and stability of perovskite solar cells (PSCs). Herein, we developed a new sulfonyldibenzene core based HTM named CS-06 , which contains substituted fluorene-terminated moieties as end groups in molecular structure. It is found that, the substituted fluorene-terminated end groups render CS-06 with a deep HOMO level, high hole mobility and glass transition temperature, which are beneficial for improving hole extraction and decreasing recombination probabilities at HTM/perovskite interface. The champion device based on CS-06 can yield a power conversion efficiency of 21.10%, superior to devices based on its analog CS-04 (19.73%) as reference. This work provides an effective way to develop efficient HTMs through rational end group design to boost the photovoltaic performance of PSCs. [Display omitted] • A sulfonyldibenzene-core based hole-transporting material (CS-06) by end group engineering. • CS-06 exhibits high hole mobility, suitable energy level and good film quality. • CS-06 enabled perovskite solar cells with high efficiency (PCE = 21.10%) and stability. [ABSTRACT FROM AUTHOR]

• Two asymmetric ACZ-containing molecules ACZ-TAD/ACZ-TPA as efficient HTMs for PeSCs. • Both the HTMs exhibited low cost, high thermal stability and superior hole mobility. • The ACZ-TAD based PSCs achieved a high PCE over 20% with negligible hysteresis. • The novel HTMs delivered excellent hydrophobicity and long-term stability. Here, the asymmetrical 8,8-dimethyl-8H-indolo[3,2,1-de]acridine (ACZ) is firstly developed as central core for hole-transporting materials (HTMs) in perovskite solar cells (PeSCs). Two asymmetrical HTMs N3,N3,N6,N6,N10,N10-hexakis(4-methoxyphenyl)-8,8-dimethyl-8H-indolo[3,2,1-de]acridine-3,6,10-triamine (ACZ-TAD) and 4,4′,4′'-(8,8-dimethyl-8H-indolo[3,2,1-de]acridine-3,6,10-triyl)tris(N,N-bis(4-methoxyphenyl) aniline) (ACZ-TPA) with different arylamines branches were designed and synthesized. This molecular design for incorporating different blocks could consolidate their merits to construct new HTMs. Meanwhile, the rigid and planar ACZ fragment results in good thermal stability, high hole mobility and suitable energy level of the materials. As a result, ACZ-TAD exhibits higher hole mobility and better charge extraction property compared with ACZ-TPA and the classical 2,2′,7,7′-tetrakis-(N,N-di-paramethoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). The high power conversion efficiencies (PCEs) of 18.72% and 20.23% are generated for ACZ-TPA and ACZ-TAD in the PeSCs device, which are both superior to spiro-OMeTAD (18.18%). Therefore, the molecular design concept in this work exhibits great potential in developing HTMs in the future. [ABSTRACT FROM AUTHOR]

Up to now, the most efficient perovskite solar cells (PSCs) typically utilize Spiro-OMeTAD as hole transporting materials (HTMs). The unique "spiro" structure offers appropriate energy levels for hole transfer and high thermal stability with suppressed aggregation. However, the pristine Spiro-OMeTAD requires additional oxidizing dopants to work efficiently due to its low hole mobility. To retain the advantages of spiral structure and overcome its shortcomings, we demonstrate the design of three dopant-free HTMs with spiral structure by molecular engineering, in which three groups with different conjugated lengths, namely benzene, naphthalene and anthracene, are inserted between spiral core and electron donor. These designed molecules, Y-1~Y-3, are initially identified with quantum chemical calculations based on the mother molecule X59 and then are obtained by easy synthetic routes. Our studies show that the intramolecular charge transfer (ICT) states are formed in the designed molecules due to the introduction of conjugated groups, which produces a self-doping effect without the need to add any external dopant. The best-performing PSCs using the dopant-free Y-1 as HTM achieves a champion power conversion efficiency (PCE) of 16.29% under one sun illumination, which is higher than that of devices with X59 as dopant-free HTMs (14.64%). The present work provides an effective strategy for designing, synthesizing of highly efficient and stable dopant-free HTMs. Image 1 • Three dopant-free HTMs with spiral structure are designed and synthesized. • The calculated results reveal that the introduced conjugated groups leads to an intramolecular charge transfer (ICT) state. • The outstanding hole mobility was predicted computationally and verified experimentally. • The perovskite solar cells (PSCs) using the dopant-free Y-1 as HTMs achieves a champion power conversion efficiency (PCE) of 16.29%. • The application of three dopant-free HTMs to PSCs can greatly improve the device stability. [ABSTRACT FROM AUTHOR]

So far, squaraine‐based polymer donors have been less explored for the bulk heterojunction (BHJ) polymer solar cells. In this work, two new p–π conjugated polysquaraines (PASQ‐BDT1 and PASQ‐BDT2) with different electron‐rich subunits on the squaraine skeleton are rationally developed as new polymer donors based on the 2D structure design concept. PASQ‐BDT2 with N,N‐diisobutylaniline subunits shows superior device performances in both fullerene and nonfullerene PSCs compared to PASQ‐BDT1 containing triphenylamine subunits, with power conversion efficiencies (PCEs) of 4.34% and 3.72%, respectively, owing to increased light‐harvesting ability and more favorable nanoscale morphology in the BHJ films. Moreover, its demonstrated that solvent effects can play an effective role in elevating the device performance. For the PASQ‐BDT2/PC71BM blend, the PCE is improved from 3.19% to 4.34% after solvent vapor annealing treatment, mainly attributed to the optimized film morphology and increased hole mobility. More interestingly, when the processing solvent for nonfullerene devices is changed from chlorobenzene to chloroform, a significant enhancement on PCE from 1.96% to 3.72% is yielded for the PASQ‐BDT2/ITIC blend, due to suppressed charge recombination and enhanced crystallinity in the chloroform‐processed BHJ films. [ABSTRACT FROM AUTHOR]

Acquiring the accurate parameter values of photovoltaic (PV) cell models paly a vital role in the controlling, simulating, evaluating and optimization of photovoltaic system. To this end, an improved evolutional algorithm called modified bare-bone imperialist competitive algorithm (MBB-ICA) is proposed to estimate the parameter of PV cell. To enhance the exploring and exploiting ability of bare-bone imperialist competitive algorithm, a complete Gaussian sampling rather than partial Gaussian sampling is adopted in MBB-ICA. The proposed MBB-ICA is applied to estimate the parameters of three types of photovoltaic cell models, i.e., single-diode model (SDM), double diode model (DDM) and photovoltaic module (PVM). The experimental results show that the root mean square error (RMSE) obtained by the proposed MBB-ICA achieves 8.5579E−04, 7.7763E−04 and 3.0552E−03 for SDM, DDM and PVM, respectively. The estimated results are better than most of the competitive algorithms. [ABSTRACT FROM AUTHOR]

Although several hole‐transporting materials (HTMs) have been designed to obtain perovskite solar cells (PSCs) devices with high performance, the dopant‐free HTMs for efficient and stable PSCs remain rare. Herein, a rigid planar 6,12‐dihydroindeno[1,2‐b]fluorine (IDF) core with different numbers of bulky periphery groups to construct dopant‐free HTMs of IDF‐SFXPh, IDF‐DiDPA, and IDF‐TeDPA is modified. Thanks to the contributions of the planar IDF core and the twisted SFX periphery groups, the dopant‐free IDF‐SFXPh‐based PSCs device achieves a device performance of 17.6%, comparable to the doped 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD)‐based device (17.6%), with much enhanced device stability under glovebox and ambient conditions. [ABSTRACT FROM AUTHOR]

In this paper, highly efficient (17%) perovskite solar cells (PSCs) based on a hole‐transporting layer (HTL) made of dopant‐free Spiro‐OMeTAD processed from a non‐halogenated solvent (THF) are reported for the first time. In addition to the high efficiency, a negligible hysteresis effect is observed for the devices with dopant‐free Spiro‐OMeTAD hole‐transporting material (HTM), which is often a problem for planar n‐i‐p type PSCs. By eliminating the hydroscopic dopants, the ambient stability of the completed PSC devices are much improved. Another advantage of using THF as a solvent is that much less of the Spiro‐OMeTAD material is required (5 mg ml−1) to coat the HTL compared to that used in a conventional chlorobenzene solvent (70 mg ml−1). Our result provides a simple yet effective method to fabricate dopant‐free PSCs toward cost‐effective and environmental friendly production of PSCs with enhanced stability. [ABSTRACT FROM AUTHOR]

The power conversion efficiency of 15.20% is achieved in this study for planar perovskite solar cells fabricated in air from one-step spin-coating lead chloride (PbCl 2 ) based precursor modified by additional adding 1% lead acetate (PbAc 2 ), much higher than the reference one from pure PbCl 2 precursor without modification. A higher quality perovskite film with increased coverage is the reason for this improvement. The perovskite nucleation rate and start time of nucleation are key parameters of perovskite crystallization kinetics. By adding 1% PbAc 2 to the precursor, the density of perovskite crystal nucleuses is optimized to achieve the best film and then the highest device performance. [ABSTRACT FROM AUTHOR]

[Display omitted] Two isomers based on fluorine-substituted sulfonyldibenzene with asymmetric molecular structure were mixed as (HTM) in conventional perovskite solar cells, with a high-power conversion efficiency of 21.41%. • The strategy of blending two isomers as hole transporting material (HTM) was firstly reported. • The two isomers show good compatibility when they are mixed. • The mixed HTM film exhibits improved hole mobility and hole extraction ability. • High efficiency (21.41%) with enhanced stability was achieved in blended HTM-based PSCs. In this article, two fluorine-substituted sulfonyldibenzene compounds are synthesized and characterized (denoted as 3, 6-SFY and 2, 7-SFY), and they are mixed as hole transport material (HTM) in conventional perovskite solar cells (PSCs). 3, 6-SFY and 2, 7-SFY show good compatibility when they are blended due to their highly similar conjugated structures. The mixed HTM film exhibits suitable energy level and uniform surface morphology. Moreover, improved hole mobility and hole extraction ability was detected in the mixed isomers-based HTM compared to the single-component HTM. As a result, conventional perovskite solar cells using the mixed isomers as HTM deliver a maximum power conversion efficiency of 21.41%, significantly higher than that obtained in 3,6-SFY (19.02%) and 2,7-SFY-based devices (20.29%). These results demonstrate that mixing two isomers as HTM is a promising way to improve device performance. As far as we know, this is the first example of blending two isomers in conventional PSCs, and the results in this work also provide a new sight in developing highly efficient hole transport materials. [ABSTRACT FROM AUTHOR]

Organic hole transport materials (HTMs) are extensively studied in perovskite solar cells (PSCs). However, due to the inherently low charge carrier mobility, chemical dopants are often required to increase mobility and achieve high power conversion efficiency. Unfortunately, the use of dopants not only brings high costs, but also accelerates the degradation of perovskite, severely reducing the stability of perovskite solar cells. Therefore, developing efficient dopant-free HTMs has become a big challenge. Here, two linear molecules DTTTP-DPA and DTTTP-TPA were designed and synthesized, with diethyl 2,5-bis(thieno [3,2-b]thiophen-2-yl)terephthalate (DTTTP) as the core structure, methoxydiphenylamine/methoxytriphenylamine as the end group, respectively. Compared to diphenylamine, the triphenylamine end group endowed DTTTP-TPA with a longer conjugation length and a lower HOMO level. The longer conjugation is more conducive to charge transporting. While the lower HOMO level due to the weaker electron donating ability of triphenylamine, is potential to achieve a higher open-circuit voltage when used in PSCs. In addition, the carbonyl group in molecular structure could passivate the defect at perovskite/hole transport layer (HTL) interface. As a result, the dopant-free DTTTP-TPA device shows a high photovoltaic performance of 21.62%. At room temperature (30% relative humidity), the initial PCE of the unencapsulated device remains above 93% after 1000 h, showing excellent stability. Our work demonstrates that constructing linear type molecular structure with extended conjugation is an efficient way to enhance hole mobility and is promising to obtain dopant-free HTMs. [Display omitted] • Two linear molecules were designed and synthesized. • 2,5-bis(thieno [3,2-b]thiophen-2-yl)terephthalate was as the core structure. • DTTTP-TPA has a long conjugation length with low HOMO level. • The carbonyl group could passivate defect at perovskite/HTL interface. • The dopant-free DTTTP-TPA device shows a high performance of 21.62%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three molecules (CX1-CX3) as HTMs are designed through methoxy management on the side chains. • Interface interaction between the HTMs and the perovskite is effected by the methoxy groups. • PSCs based on CX1 yields a PCE of 22.13% higher than those of CX2 (20.96%) and CX3 (19.72%). • Methoxy management on molecular chain is an effective strategy to design potential HTMs. Molecular design is the important approach for realizing the improvement of performance for hole transport materials (HTMs) in perovskite solar cells (PSCs). In this work, starting from the carbazole-diphenylamine derivatives based HTMs, three molecules (CX1-CX3) are designed through methoxy management on the side chains. The calculated results indicated that CX1-CX3 yield different molecular arrangements through methoxy management on the side chains, resulting in adjusting the intermolecular coupling strength and hole transport capabilities. In comparison with the designed CX2 and CX3, CX1 exhibits a higher hole mobility, stronger interfacial interactions and more efficient charge transfer at perovskite/HTMs interface. Hence, under the same conditions, PSC devices based on CX1 yields a PCE of 22.13% higher than those of other molecules CX2 (20.96%) and CX3 (19.72%). These findings highlight the significance of methoxy management on the side chains in HTMs for the photovoltaic performance of PSCs, and reveal the potential of molecular engineering for the design of efficient HTMs. [ABSTRACT FROM AUTHOR]

A series of tetraphenylethylene-diketopyrrolopyrrole (TPE-DPP) derivatives with different alkyl chains were synthesized and characterized. The effects of alkyl chains on the electronic property of these compounds and the performance of perovskite solar cells (PSCs) were investigated. Cyclic voltammetry results suggest that different alkyl chains have little influence on the molecular energy levels of these TPE-DPP derivatives. AFM (atomic force microscopy) images indicate that among the derivatives studied, TPE-DPP derivative with 2-butyloctyl (TPE-DPPC12) shows the most smooth surface morphology on top of the perovskite layer, ensuring a good charge selective contact. Time-resolved photoluminescence (PL) spectra indicate that the TPE-DPPC12 shows the best electron extraction ability. As a result, the device with TPE-DPPC12 interlayer exhibited an average power conversion efficiency (PCE) of 18.37%, corresponding to an increase of 17% relative to the control device (16.37%). In addition, considering the hydrophobic nature of TPE-DPPC12, the ambient stability of inverted PSCs incorporating the TPE-DPPC12 interlayer is also improved. This study provides an effective design strategy for electron extraction materials to achieve highly-efficient PSCs with improved stability. A series of tetraphenylethylene-diketopyrrolopyrrole (TPE-DPP) derivatives with different alkyl chain lengths are used as interfacial materials. Perovskite solar cells using the TPE-DPP derivative with 2-butyloctyl group (TPE-DPPC12) is superior to the other three TPE-DPP derivatives, and achieved a high efficiency of 18.93%. Image 1 • The effect of alkyl chain lengths on the performance of PSCs was investigated. • Alkyl chain of TPE-DPP derivatives has negligible effect on the energy level. • TPE-DPPC12 exhibited good electron extraction ability. • TPE-DPPC12 exhibited good film quality and smooth surface. • Device with TPE-DPPC12 interlayer achieve a champion efficiency of 18.93%. [ABSTRACT FROM AUTHOR]

Two new compounds (J1 and J2) are synthesized and used as hole transport materials (HTMs) for perovskite solar cells (PSCs). In J1 and J2, 1,2-dimethoxyphenyl is used as the terminal group, with tetraphenyl ethylene and 9,​9′-​spirobi[9 H -​fluorene] ring as the core structure, respectively. Compared to the commonly used methoxyl end group, there are two methoxyl units on 1,2-dimethoxyphenyl, which enhances the electron-donating ability of the end groups. Additionally, the introduced phenyl ring could extend π conjugation of the whole molecule, which is favorable for electron delocalization and charge transporting. Planar PSCs are fabricated, and J2-based device shows a power conversion efficiency (PCE) of 15.07%, with a short-circuit current density ( J sc ) of 20.37 mA cm −2 , an open-circuit voltage ( V oc ) of 1020 mV and a fill factor ( FF ) of 0.73. [ABSTRACT FROM AUTHOR]

Spiro-OMeTAD represents the benchmark hole transport material (HTM) in the state-of-the-art perovskite solar cells (PSCs). However, restricted by the low conductivity of pristine spiro-OMeTAD, dopants and a long oxidation process are required to improve the conductivity and hole mobility. The long oxidation in air not only prolongs the device fabrication period, but also leads to the decomposition of perovskite layer. Even worse, dopants such as tBP and Li-TFSI will be severely affected and cause irreversible damage during the long oxidation process, which will greatly affect the device performances. In this regard, a strong oxidant lead tetraacetate (LTA) is introduced into spiro-OMeTAD to significantly accelerate the oxidation process. Excitingly, the Pb2+ ions generate as a result of the reduction of LTA could strongly coordinate with tBP, thus hindering the evaporation of tBP, as well as the agglomeration of Li-TFSI. As a result, the PSCs based on LTA-doped spiro-OMeTAD show a high photo-to-electric conversion efficiency of 22.08% with excellent long-term stability and thermal stability. Overall speaking, LTA is commercially available and low-cost, more importantly, the accelerate oxidation process as well as the effect to stabilize the dopants in spiro-OMeTAD, makes it potential as a p-dopant for highly efficient and stable PSCs. [Display omitted] • Lead tetraacetate (LTA) could rapidly oxidize spiro-OMeTAD and thus improve conductivity and hole mobility. • The Pb2+ ions generated from the reduction of LTA could coordinate with tBP to slow down its evaporation. • PSCs based on LTA-doped spiro-OMeTAD showed a high photo-to-electric conversion efficiency (PCE) of 22.08 %. • The efficiency of LTA-doped device maintained 81 % of the initial value after the device was heated at 65 ℃ for 450 h. [ABSTRACT FROM AUTHOR]

The development of hole-transport materials (HTMs) is a significant approach to promote the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Here, based on the triphenylamine (TPA) derivatives and patulous TPA derivatives as side-chains, WR1 and WR2 are designed and explored by density functional theory (DFT), time-dependent DFT (TD-DFT) in combination with Marcus electron transfer theory. The calculated results show that the WR1 exhibits matching energy levels with perovskite and better hole transporting ability in comparison with these of WR2 can save as a potential HTM for PSCs applications. In order to confirm screening results of molecular design, the WR1 as HTM in PSC device reveals that the WR1-based PSC device obtained the PCE of 20.04% higher than that of the typical Spiro-OMeTAD-based device (18.84%). Moreover, the experimental results can well verify the data of theoretical simulations. The strategy of side-chain modification on TPA derivatives-based materials is a viable method to exploit new HTMs. [Display omitted] • WR1 and WR2 with triphenylamine (TPA) derivatives and patulous TPA derivatives as side-chains are designed. • The HTMs of WR1 and WR2 were investigated by theoretical simulation and experimental exploration. • The experimental data verified the provided theoretical model. • Side-chain engineering on triphenylamine derivative-based HTMs are feasible. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of the modulated core on the properties of HTMs and PSCs was explored. • Two HTMs of biphenyl core-based HY5 and pyrene core-based HY6 were designed. • Pyrene core-based HY6 exhibits better planarity and higher hole mobility than HY5. • The HY6-based devices are higher efficiency than that of Spiro-OMeTAD. • Rational extension of π-bridge is an effective strategy to design potential HTMs. Rational design of hole transport materials (HTMs) is an important way to improve the performance of perovskite solar cells (PSCs). In this work, on basis of the biphenyl and pyrene cores, two methoxyaniline derivatives-based HTMs of HY5 and HY6 have been designed, aiming to explore the influence of the modulated π-bridged cores on the properties of HTMs and the performances of PSC devices. On basis of DFT and TD-DFT combined with Marcus theory, the computational results show the pyrene core endows HY6 with a more planarity and stronger conjugation than the biphenyl core of HY5 , which promotes the delocalization of π electrons and the π–π stacking for improvement of the hole transporting. Therefore, the HY6 -based device achieved a power conversion efficiency (PCE) (19.34 %) superior to the HY5 (15.50 %) and Spiro-OMeTAD (18.33 %) based devices. Conclusively, rational modulation of π-bridge conjugation is a feasible strategy to obtain the potential HTMs for improvement of the PSCs performance. [ABSTRACT FROM AUTHOR]

At present, organic small molecule-based hole transporting materials (HTMs) are extensively investigated in perovskite solar cells (PSCs), and a variety of structures have been developed. Most of the studies in HTMs focus on the central scaffolds, while little attention is paid to the periphery groups. In this work, two small organic molecules (TPE-2Cz and TPE-3Cz) are designed and synthesized, with tetraphenylethylene as the core structure, N -ethylcarbazole and methoxyphenyl as the peripheral groups. The C 2 or C 3 position on N -ethylcarbazole is connected to the arylamine N atom in TPE-2Cz and TPE-3Cz, respectively. We systematically investigate how the N -ethylcarbazole modified at different positions (C 2 or C 3) affect the property of HTMs and finally the performance of PSC devices. Compared with TPE-2Cz, TPE-3Cz shows a higher hole mobility, better hole extraction and hole transport ability. The device based on TPE-3Cz as the hole transport material achieves a decent power conversion efficiency of 20.94%. Therefore, our work reveals that the periphery group engineering should be taken into consideration when designing organic HTMs. [Display omitted] • Two small organic molecules were designed and synthesized, with N -ethylcarbazole as the peripheral groups. • In TPE-2Cz and TPE-3Cz, the effect of substitution position was systematically discussed. • The TPE-3Cz-based device shows a decent power conversion efficiency of 20.94%. [ABSTRACT FROM AUTHOR]

Modulation on peripheral groups of hole-transporting materials (HTMs) is a feasible way to control the properties of the energy levels, optical absorption, solubility and hole mobility, to enhance the efficiency of perovskite solar cells (PSCs). In this work, two carbazole core-based HTMs (CQ7 and CQ8) with different peripheral groups are designed. In comparison of Spiro-OMeTAD and CQ8, simulated results show that CQ7 can act as potential HTMs for PSC devices due to its suitable energy levels, good solubility and better hole-transporting ability. To verify the reliability of the simulated results, the molecules CQ7 and CQ8 are synthesized and used to fabricate the PSCs. The experimental results indicates that the PSC device based on CQ7 as HTM yield a 19.60% of power conversion efficiency (PCE), which is higher than that of Spiro-OMeTAD (18.19%) and CQ8 (15.58%) under the same conditions. This is mainly reflected in the improved fill factor and short-circuit current, which is attributed to better hole transport in the CQ7 film and faster hole extraction at the perovskite/CQ7 interface. Conclusively, the experimental data confirm the reliability of the simulation results while providing the feasibility of molecular design strategies to obtain the potential HTMs by adjusting the peripheral groups. [Display omitted] • A theoretical model was provided for the design of potential HTMs. • Two HTMs (CQ7 and CQ8) with different peripheral groups were designed. • The promising CQ7 and CQ8 material were synthesized for perovskite solar cell application. • The provided theoretical model was verified by experimental data. [ABSTRACT FROM AUTHOR]

Ternary blend solar cells have been proved to be an efficient way to harvest more photons over the near-IR region. In this work, the effect of adding a NIR absorbing squaraine derivative (TPE-SQ) into a conventional P3HT:PC 71 BM based bulk heterojunction photovoltaic cell is investigated. The new NIR dye exhibits a quite broad absorption band with full-width at half maximum of 169 nm in the film state, with the absorption edge extending to more than 850 nm. The near infrared absorption of the ternary system is enhanced by the blended squaraine component, and the energy level of the third component matched well with the donor and the acceptor material, leading to increased short-circuit current as well as elevated power conversion efficiency compared to the P3HT:PC 71 BM binary solar cell. The highest efficiency of 3.93% is achieved for a P3HT:PC 71 BM blend with 2.4 wt % of TPE-SQ. [ABSTRACT FROM AUTHOR]

A new green-solvent-processable dopant-free hole transport material F23 was developed for efficient and stable perovskite solar cells, with a high power conversion efficiency of 17.6%. • F23 was developed as dopant-free hole transport material (HTM) in perovskite solar cells (PSCs). • Nonhalogenated green solvent tetrahydrofuran (THF) is used for F23 film fabricating and only small amount is required. • F23 film exhibits uniform and smooth morphology, with excellent hole transport property. • High efficiency (17.60%) with enhanced stability was achieved in F23-based PSCs. At present, dopant-free hole transport materials (HTMs) have been largely explored to improve the performance and stability of perovskite solar cells (PSCs), and significant progresses have been made. In current reports, chlorobenzene is the most commonly used solvent to dissolve HTMs in PSCs. Dopant-free HTMs based on green solvent were rarely reported yet. Here in this work we synthesized a new dopant-free HTM F23, which could be processed with the nonhalogenated and environmental-friendly green solvent tetrahydrofuran (THF). Interestingly, F23 film prepared using THF as solvent exhibits uniform and smooth morphology, with excellent hole transport property. In addition, the process requires only a small amount of F23 (3 mg/mL), thus further lowering the costs in device fabrication. As a result, device using dopant-free F23 prepared in THF as HTM exhibited a high power conversion efficiency (PCE) of 17.60%, with enhanced stability. [ABSTRACT FROM AUTHOR]