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Accurately predicting the power conversion efficiency (PCE) in dye‐sensitized solar cells (DSSCs) represents a crucial challenge, one that is pivotal for the high throughput rational design and screening of promising dye sensitizers. This study presents precise, predictive, and interpretable machine learning (ML) models specifically designed for Zn‐porphyrin‐sensitized solar cells. The model leverages theoretically computable, effective, and reusable molecular descriptors (MDs) to address this challenge. The models achieve excellent performance on a "blind test" of 17 newly designed cells, with a mean absolute error (MAE) of 1.02%. Notably, 10 dyes are predicted within a 1% error margin. These results validate the ML models and their importance in exploring uncharted chemical spaces of Zn‐porphyrins. SHAP analysis identifies crucial MDs that align well with experimental observations, providing valuable chemical guidelines for the rational design of dyes in DSSCs. These predictive ML models enable efficient in silico screening, significantly reducing analysis time for photovoltaic cells. Promising Zn‐porphyrin‐based dyes with exceptional PCE are identified, facilitating high‐throughput virtual screening. The prediction tool is publicly accessible at https://ai‐meta.chem.ncu.edu.tw/dsc‐meta. [ABSTRACT FROM AUTHOR]

A series of two‐dimensionally expanded azulene‐core‐based π systems have been synthesized with different alkyl chain lengths in the alkoxy moieties connected to the partially oxygen‐bridged triarylamine skeletons. The thermal, photophysical, and electronic properties of each compound were evaluated to determine the influence of the alkyl chain length on their effectiveness as hole‐transporting materials (HTMs) in perovskite solar cells (PSCs). All the synthesized molecules showed promising material properties, including high solubility, the formation of flat and amorphous films, and optimal alignment of energy levels with perovskites. In particular, the derivatives with methyl and n‐butyl in the side chains retained amorphous stability up to 233 and 159 °C, respectively. Such short alkoxy chains also resulted in improved electrical device properties. The PSC device fabricated with the HTM with n‐butyl side chains showed the best performance with a power conversion efficiency of 18.9 %, which compares favorably with that of spiro‐OMeTAD‐based PSCs (spiro‐OMeTAD=2,2′,7,7′‐tetrakis[N,N‐bis(p‐methoxyphenyl)amino]‐9,9′‐spirobifluorene). [ABSTRACT FROM AUTHOR]

High photovoltage in perovskite solar cells (PSCs) can be achieved by designing new hole transporting materials (HTMs) with relatively deeper energy levels of the highest occupied molecular orbital (HOMO). Here, we report on the synthesis of a new heteroacene‐based HTM (HTM‐1) and demonstrate its potential in the fabrication of FAPbBr3 [FA = CH(NH2)2] PSCs yielding VOC as high as 1.55 V, a record value for this light harvester. The energetic position of the frontier orbitals of HTM‐1 was estimated using electrochemical measurements, and the charge transport across the interfaces was studied using steady‐state and time‐resolved photoluminescence. When spiro‐OMeTAD (HOMO = –5.1 eV) is replaced with HTM‐1 (HOMO = –5.3 eV), the VOC increases from 1.51 to 1.55 V, whereas the JSC value decreases from 7.0 to 5.7 mA cm–2. The similar trade‐off between JSC and VOC is observed for efficient iodide‐based PSCs, suggesting that there is a critical energy level for the HOMO below which overall photovoltaic performance will suffer. After probing at a maximum power point under full‐sun illumination at 60 °C for a duration of 120 h, the FAPbBr3 PSCs based on HTM‐1 retained ≈ 95 % of their initial efficiency, which demonstrates their robust operational stability. A new heteroacene‐based hole transporting material (HTM) was designed and used in the fabrication of FAPbBr3 [FA = CH(NH2)2] robust solar cells yielding a VOC of 1.55 V, a record value for this light harvester. A trade‐off between JSC and VOC was observed when the HOMO level was lowered, suggesting that there is a critical energy level for the HOMO, below which overall photovoltaic performance will suffer. [ABSTRACT FROM AUTHOR]

The pressure to move towards renewable energy has inspired researchers to look for ideas in photovoltaics that may lead to a major breakthrough. Recently the use of perovskites as a light harvester has lead to stunning progress. The power conversion efficiency of perovskite solar cells is now approaching parity (>22 %) with that of the established technology which took decades to reach this level of performance. The use of a hole transport material (HTM) remains indispensable in perovskite solar cells. Perovskites can conduct holes, but they are present at low levels, and for efficient charge extraction a HTM layer is a prerequisite. Herein we provide an overview of the diverse types of HTM available, from organic to inorganic, in the hope of encouraging further research and the optimization of these materials. [ABSTRACT FROM AUTHOR]

The photovoltaic performance of perovskite solar cells (PVSCs) is extremely dependent on the morphology and crystallization of the perovskite film, which is affected by the deposition method. In this work, a new approach is demonstrated for forming the PbI2 nanostructure and the use of high CH3 N3 I concentration which are adopted to form high-quality (smooth and PbI2 residue-free) perovskite film with better photovoltaic performances. On the one hand, self-assembled porous PbI2 is formed by incorporating small amount of rationally chosen additives into the PbI2 precursor solutions, which significantly facilitate the conversion of perovskite without any PbI2 residue. On the other hand, by employing a relatively high CH3NH3 I concentration, a firmly crystallized and uniform CH3NH3 PbI3 film is formed. As a result, a promising power conversion efficiency of 16.21% is achieved in planar-heterojunction PVSCs. Furthermore, it is experimentally demonstrated that the PbI2 residue in perovskite film has a negative effect on the long-term stability of devices. [ABSTRACT FROM AUTHOR]

The success of perovskite solar cells has sparked enormous excitement in the photovoltaic community not only because of unexpectedly high efficiencies but also because of the future potential ascribed to such crystalline absorber materials. Far from being exhaustively studied in terms of solid-state properties, these materials surprised by anomalies such as a huge apparent low-frequency dielectric constant and pronounced hysteretic current-voltage behavior. Here we show that methylammonium (but also formamidinium) iodoplumbates are mixed conductors with a large fraction of ion conduction because of iodine ions. In particular, we measure and model the stoichiometric polarization caused by the mixed conduction and demonstrate that the above anomalies can be explained by the build-up of stoichiometric gradients as a consequence of ion blocking interfaces. These findings provide insight into electrical charge transport in the hybrid organic-inorganic lead halide solar cells as well as into new possibilities of improving the photovoltaic performance by controlling the ionic disorder. [ABSTRACT FROM AUTHOR]

Strong electron-donating functionality is desirable for many organic donor-π-bridge-acceptor (D-π-A) dyes. Strategies for increasing the electron-donating strength of common nitrogen-based donors include planarization of nitrogen substituents and the use of low resonance-stabilized energy aromatic ring-substituted nitrogen atoms. Organic donor motifs based on the planar nitrogen containing heterocycle indolizine are synthesized and incorporated into dye-sensitized solar cell (DSC) sensitizers. Resonance active substitutions at several positions on indolizine in conjugation with the D-π-A π-system are examined computationally and experimentally. The indolizine-based donors are observed to contribute electron density with strengths greater than triarylamines and diarylamines, as evidenced by UV/Vis, IR absorptions, and oxidation potential measurements. Fluorescence lifetime studies in solution and on TiO2 yield insights in understanding the performance of indolizine-based dyes in DSC devices. [ABSTRACT FROM AUTHOR]

The use of porphyrin-based photosensitizers with superior light-harvesting properties has enabled the power conversion efficiency of dye-sensitized solar cells (DSCs) to reach 13 % under full sun illumination. However, a major limitation of such devices corresponds to the volatility of the solvent used so far for the electrolyte, which prevents practical applications. In this work, we describe a porphyrin-ionic liquid DSC, which not only affords the highest efficiency reported to date, but is also stable for more than 300 h under continuous full sun illumination at 60 °C. Furthermore, we identify a previously unreported pathway for device degradation, and show that the addition of N-methylbenzimidazole and a thiocyanate salt to the electrolyte is critical to obtaining long-lived devices. [ABSTRACT FROM AUTHOR]

We report a novel electron-rich molecule based on 3,4-ethylenedioxythiophene (H101). When used as the hole-transporting layer in a perovskite-based solar cell, the power-conversion efficiency reached 13.8 % under AM 1.5G solar simulation. This result is comparable with that obtained using the well-known hole transporting material 2,2′,7,7′-tetrakis( N, N-di- p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). This is the first heterocycle-containing material achieving >10 % efficiency in such devices, and has great potential to replace the expensive spiro-OMeTAD given its much simpler and cheaper synthesis. [ABSTRACT FROM AUTHOR]

Hybrid organic-inorganic lead halide perovskite APbX3 pigments, such as methylammonium lead iodide, have recently emerged as excellent light harvesters in solid-state mesoscopic solar cells. An important target for the further improvement of the performance of perovskite-based photovoltaics is to extend their optical-absorption onset further into the red to enhance solar-light harvesting. Herein, we show that this goal can be reached by using a mixture of formamidinium (HN=CHNH3+, FA) and methylammonium (CH3NH3+, MA) cations in the A position of the APbI3 perovskite structure. This combination leads to an enhanced short-circuit current and thus superior devices to those based on only CH3NH3+. This concept has not been applied previously in perovskite-based solar cells. It shows great potential as a versatile tool to tune the structural, electrical, and optoelectronic properties of the light-harvesting materials. [ABSTRACT FROM AUTHOR]

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Porphyrins have drawn much attention as sensitizers owing to the large absorption coefficients of their Soret and Q bands in the visible region. In a donor and acceptor zinc porphyrin we applied a new strategy of introducing 2,1,3-benzothiadiazole (BTD) as a π-conjugated linker between the anchoring group and the porphyrin chromophore to broaden the absorption spectra to fill the valley between the Soret and Q bands. With this novel approach, we observed 12.75 % power-conversion efficiency under simulated one-sun illumination (AM1.5G, 100 mW cm−2). In this study, we showed the importance of introducing the phenyl group as a spacer between the BTD and the zinc porphyrin in achieving high power-conversion efficiencies. Time-resolved fluorescence, transient-photocurrent-decay, and transient-photovoltage-decay measurements were employed to determine the electron-injection dynamics and the lifetime of the photogenerated charge carriers. [ABSTRACT FROM AUTHOR]

Quasi type-II PbSe/PbS quantum dots (QDs) are employed in a solid state high efficiency QD/TiO2 heterojunction solar cell. The QDs are deposited using layer-by-layer deposition on a half-micrometer-thick anatase TiO2 nanosheet film with (001) exposed facets. Theoretical calculations show that the carriers in PbSe/PbS quasi type-II QDs are delocalized over the entire core/shell structure, which results in better QD film conductivity compared to PbSe QDs. Moreover, PbS shell permits better stability and facile electron injection from the QDs to the TiO2 nanosheets. To complete the electrical circuit of the solar cell, a Au film is evaporated as a back contact on top of the QDs. This PbSe/PbS QD/TiO2 heterojunction solar cell produces a light to electric power conversion efficiency ( η) of 4% with short circuit photocurrent ( Jsc) of 17.3 mA/cm2. This report demonstrates highly efficient core/shell near infrared QDs in a QD/TiO2 heterojunction solar cell. [ABSTRACT FROM AUTHOR]

In this paper, a way of utilizing thin and conformal overlayer of titanium dioxide on an insulating mesoporous template as a photoanode for dye-sensitized solar cells is presented. Different thicknesses of TiO2 ranging from 1 to 15 nm are deposited on the surface of the template by atomic layer deposition. This systematic study helps unraveling the minimum critical thickness of the TiO2 overlayer required to transport the photogenerated electrons efficiently. A merely 6-nm-thick TiO2 film on a 3-μm mesoporous insulating substrate is shown to transport 8 mA/cm2 of photocurrent density along with ≈900 mV of open-circuit potential when using our standard donor-π-acceptor sensitizer and Co(bipyridine) redox mediator. [ABSTRACT FROM AUTHOR]

The paradigm shift in dye sensitized solar cells (DSCs) - towards donor- p bridge-acceptor (D-π-A) dyes - increases the performances of DSCs and challenges established design principles. Framed by this shifting landscape, a series of four diketopyrrolopyrrole (DPP)-based sensitizers utilizing the donor-chromophoreanchor (D-C-A) motif were investigated computationally, spectroscopically, and fabricated by systematic evaluation of finished photovoltaic cells. In all cases, the [Co(bpy)3]3+/2+ redox-shuttle afforded superior performance compared to I3 -/I-. Aesthetically, careful molecular engineering of the DPP chromophore yielded the first example of a high-performance blue DSC - a challenge unmet since the inception of this photovoltaic technology: DPP17 yields over 10% power conversion efficiency (PCE) with the [Co(bpy)3]3+/2+ electrolyte at full AM 1.5 G simulated sun light. [ABSTRACT FROM AUTHOR]

Ruthenium und Co: Ruthenium(II) ‐ Komplexe sind nach wie vor die „heißesten Kandidaten“ für Farbstoffsolarzellen, doch derzeit bekannte Ru ‐ Sensibilisatoren sind nicht mit CoII/III ‐ Elektrolyten kompatibel. Der Effekt einer Oberflächenisolierung auf die Leistungsfähigkeit einer Zelle wurde durch den Vergleich zweier cyclometallierter RuII ‐ Komplexe studiert. Der Ansatz zeigt ein allgemeines Prinzip für beispiellose Effizienzen bei der Kombination von RuII ‐ Sensibilisatoren mit einem Cobalt ‐ Elektrolyt. [ABSTRACT FROM AUTHOR]

Following pioneering work, solution-processable organic-inorganic hybrid perovskites-such as CH3NH3PbX3 (X = Cl, Br, I)-have attracted attention as light-harvesting materials for mesoscopic solar cells. So far, the perovskite pigment has been deposited in a single step onto mesoporous metal oxide films using a mixture of PbX2 and CH3NH3X in a common solvent. However, the uncontrolled precipitation of the perovskite produces large morphological variations, resulting in a wide spread of photovoltaic performance in the resulting devices, which hampers the prospects for practical applications. Here we describe a sequential deposition method for the formation of the perovskite pigment within the porous metal oxide film. PbI2 is first introduced from solution into a nanoporous titanium dioxide film and subsequently transformed into the perovskite by exposing it to a solution of CH3NH3I. We find that the conversion occurs within the nanoporous host as soon as the two components come into contact, permitting much better control over the perovskite morphology than is possible with the previously employed route. Using this technique for the fabrication of solid-state mesoscopic solar cells greatly increases the reproducibility of their performance and allows us to achieve a power conversion efficiency of approximately 15 per cent (measured under standard AM1.5G test conditions on solar zenith angle, solar light intensity and cell temperature). This two-step method should provide new opportunities for the fabrication of solution-processed photovoltaic cells with unprecedented power conversion efficiencies and high stability equal to or even greater than those of today's best thin-film photovoltaic devices. [ABSTRACT FROM AUTHOR]

A series of squaraine-based sensitizers with various π bridges and anchors were prepared and examined in dye-sensitized solar cells. The carboxylic anchor group was attached onto a squaraine dye through π bridges with and without an ethynyl spacer. DFT studies indicate that the LUMO is delocalized throughout the dyes, whilst the HOMO resides on the squaraine core. The dye that incorporates a 4,4-di- n-hexyl-cyclopentadithiophene group that is directly attached onto the π bridge, JD10, exhibits the highest power conversion efficiency in a DSC; this result is attributed, in part, to the deaggregative properties that are associated with the gem-di- n-hexyl substituents, which extend above and below the π-conjugated dye plane. Dye JD10 demonstrates a power-conversion efficiency of 7.3 % for liquid-electrolyte dye-sensitized solar cells and 7.9 % for cells that are co-sensitized by another metal-free dye, D35, which substantially exceed the performance of any previously tested squaraine sensitizer. A panchromatic incident-photon-to-current-conversion efficiency curve is realized for this dye with an excellent short-circuit current of 18.0 mA cm−2. This current is higher than that seen for other squaraine dyes, partially owing to a high molar absorptivity of >5 000 M−1 cm−1 from 400 nm to the long-wavelength onset of 724 nm for dye JD10. [ABSTRACT FROM AUTHOR]

Batteries, fuel cells and solar cells, among many other high-current-density devices, could benefit from the precise meso- to macroscopic structure control afforded by the silica sol-gel process. The porous materials made by silica sol-gel chemistry are typically insulators, however, which has restricted their application. Here we present a simple, yet highly versatile silica sol-gel process built around a multifunctional sol-gel precursor that is derived from the following: amino acids, hydroxy acids or peptides; a silicon alkoxide; and a metal acetate. This approach allows a wide range of biological functionalities and metals-including noble metals-to be combined into a library of sol-gel materials with a high degree of control over composition and structure. We demonstrate that the sol-gel process based on these precursors is compatible with block-copolymer self-assembly, colloidal crystal templating and the Stöber process. As a result of the exceptionally high metal content, these materials can be thermally processed to make porous nanocomposites with metallic percolation networks that have an electrical conductivity of over 1,000?S?cm?1. This improves the electrical conductivity of porous silica sol-gel nanocomposites by three orders of magnitude over existing approaches, opening applications to high-current-density devices. [ABSTRACT FROM AUTHOR]

Summary: The high molar extinction coefficient heteroleptic ruthenium dye, NaRu(4,4′-bis(5-(hexylthio)thiophen-2-yl)-2,2′-bipyridine) (4-carboxylic acid-4′-carboxylate-2,2′-bipyridine) (NCS)2, exhibits certified 5% electric power conversion efficiency at AM 1.5 solar irradiation (100mWcm−2) in a solid-state dye-sensitized solar cell using 2,2′,7,7′-tetrakis-(N,N-di-pmethoxyphenylamine)-9,9′-spirobifluorene (spiro-MeOTAD) as the organic hole-transporting material. This demonstration elucidates a class of photovoltaic devices with potential for low-cost power generation. [Copyright &y& Elsevier]

Solar energy is a promising solution to global energy-related problems because it is clean, inexhaustible and readily available. However, the deployment of conventional photovoltaic cells based on silicon is still limited by cost, so alternative, more cost-effective approaches are sought. Here we report a bifacial dye-sensitized solar cell structure that provides high photo-energy conversion efficiency (∼6%) for incident light striking its front or rear surfaces. The design comprises a highly stable ruthenium dye (Z907Na) in combination with an ionic-liquid electrolyte and a porous TiO2 layer. The inclusion of a SiO2 layer between the electrodes to prevent generation of unwanted back current and optimization of the thickness of the TiO2 layer are responsible for the enhanced performance. [ABSTRACT FROM AUTHOR]

Abstract: Counter electrodes (CEs) of dye-sensitized solar cells (DSCs) can be prepared with different materials and methods. This review covers recent research on CEs using platinum, graphite, activated carbon, carbon black, single-wall carbon nanotubes, poly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole, and polyaniline as catalysts for reduction of triiodide. Moreover, for the ultimate in low-cost counter electrodes, we have prepared a carbon-black-loaded stainless steel electrode for use as a novel CE. This counter electrode exhibits good photovoltaic performance; the efficiency reaches 9.15% (16.3mAcm−2 J sc, 785mV V oc, and 71.4% fill factor) with SUS-316 stainless steel, equivalent to the performance with an FTO-glass substrate. [Copyright &y& Elsevier]

Abstract: The efficiency of electric power generation by dye-sensitized mesoscopic photovoltaic cells has been progressing steadily over the last years reaching now 11% in full sunlight. An important question for practical applications concerns the stability of these devices under prolonged exposure to light or heat. Strikingly stable operation can be obtained by judicious selection of the sensitizer, electrolyte and sealant rendering feasible a service life of at least 20 years under normal outdoor conditions. The sensitizer playing a central role in the light energy conversion process, we analyze the kinetic requirements for it to sustain the required one hundred million turnovers. We also review recent results on the use of self-assembled monolayers of amphiphilic sensitizers and co-adsorbents to enhance the thermal robustness of the device. To cite this article: M. Grätzel, C. R. Chimie 9 (2006) . [Copyright &y& Elsevier]

The dye-sensitized solar cells (DSC) provides a technically and economically credible alternative concept to present day p–n junction photovoltaic devices. In contrast to the conventional systems where the semiconductor assume both the task of light absorption and charge carrier transport the two functions are separated here. Light is absorbed by a sensitizer, which is anchored to the surface of a wide band semiconductor. Charge separation takes place at the interface via photo-induced electron injection from the dye into the conduction band of the solid. Carriers are transported in the conduction band of the semiconductor to the charge collector. The use of sensitizers having a broad absorption band in conjunction with oxide films of nanocrstalline morphology permits to harvest a large fraction of sunlight. Nearly quantitative conversion of incident photon into electric current is achieved over a large spectral range extending from the UV to the near IR region. Overall solar (standard AM 1.5) to current conversion efficiencies (IPCE) over 10% have been reached. There are good prospects to produce these cells at lower cost than conventional devices. Here we present the current state of the field, discuss new concepts of the dye-sensitized nanocrystalline solar cell (DSC) including heterojunction variants and analyze the perspectives for the future development of the technology. [Copyright &y& Elsevier]

We demonstrate a >=8% efficient nanocrystalline dye-sensitized solar cell retaining over 98% of its initial performance after 1000 h of accelerated tests subjected to thermal stress at 80 °C in the dark. Device degradation was also negligible following 1000 h of visible light soaking at 60 °C. This high performance and stable device was realized by using a robust electrolyte of low volatility in conjunction with the amphiphilic ruthenium sensitizer [Ru(4,4′-dicarboxylic acid-2,2′-bipyridine)(4,4′-bis(p-hexyloxystyryl)-2,2′-bipyridine)(NCS)2], coded as K-19, which was grafted together with 1-decylphosphonic acid on the mesoporous titania film acting as photoanode. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this brief review is to give a short and simple overview of the dye-sensitized solar cell technology from the working principles to the first commercial applications. It emphasizes the role of the sensitizer and the strategies to improve the performances of the dye as well as some recent development aiming to answer specific issues. [Copyright &y& Elsevier]

Abstract: Three new triethoxysilanes bearing quaternary ammonium alkyl iodides are reported, N,N,N-triethyl-3-(triethoxysilyl)propan-1-aminium iodide 1, N,N,N-triheptyl-3-(triethoxysilyl)propan-1-aminium iodide 2 and N,N,N-tridodecyl-3-(triethoxysilyl)propan-1-aminium iodide 3. 1H and 13C NMR spectroscopy and electrospray mass spectrometry were used to confirm the synthesis of pure products. Electrolytes based on these ionic liquids were developed and their performance in dye-sensitized solar cells (DSSCs) evaluated. The electrolytes incorporated 1 and 2 (in 30–60wt%) as iodide sources together with I2 (0.08M), 0.1M guanidinium thiocyanate and 0.5M tert-butylpyridine in acetonitrile (AN); and I2 (0.15M) and N-methylbenzimidazole (0.5M) for 2-methoxyproprionitrile (MPN) as co-solvent. Testing of DSSCs to analyze the influence of chain length (ethyl and heptyl) on cell efficiency revealed that, for silanes concentration of 1M, electrolyte B (based on 2 in AN) and electrolyte C (based on 1 in MPN) gave the best cell efficiency at simulated full sunlight (AM 1.5, 1000Wm−2) illumination (5.0–5.3%). At 0.1 Sunlight (AM 1.5, 100Wm−2), electrolyte B gave the best performance of 8.0%. High open circuit voltages (V OC) of 750–850mV were achieved for a number of quite efficient cells (5–6%). For silane 2, variation of the I−/I2 ratio and total silane content (1–2M 2) on DSSC efficiency gave a consistent efficiency of 8.0% at 0.1 Sunlight. At full sunlight, the cell efficiency decreased as the silane concentration increased from 1M (5.0%) to 2M (3.7%), largely due to a drop in short circuit current. [Copyright &y& Elsevier]

Improvements to perovskite solar cells (PSCs) have focused on increasing their power conversion efficiency (PCE) and operational stability and maintaining high performance upon scale-up to module sizes. We report that replacing the commonly used mesoporous–titanium dioxide electron transport layer (ETL) with a thin layer of polyacrylic acid–stabilized tin(IV) oxide quantum dots (paa-QD-SnO2) on the compact–titanium dioxide enhanced light capture and largely suppressed nonradiative recombination at the ETL–perovskite interface. The use of paa-QD-SnO2 as electron-selective contact enabled PSCs (0.08 square centimeters) with a PCE of 25.7% (certified 25.4%) and high operational stability and facilitated the scale-up of the PSCs to larger areas. PCEs of 23.3, 21.7, and 20.6% were achieved for PSCs with active areas of 1, 20, and 64 square centimeters, respectively. [ABSTRACT FROM AUTHOR]

The efficiencies of perovskite solar cells have gone from single digits to a certified 22.1% in a few years’ time. At this stage of their development, the key issues concern how to achieve further improvements in efficiency and long-term stability. We review recent developments in the quest to improve the current state of the art. Because photocurrents are near the theoretical maximum, our focus is on efforts to increase open-circuit voltage by means of improving charge-selective contacts and charge carrier lifetimes in perovskites via processes such as ion tailoring. The challenges associated with long-term perovskite solar cell device stability include the role of testing protocols, ionic movement affecting performance metrics over extended periods of time, and determination of the best ways to counteract degradation mechanisms. [ABSTRACT FROM AUTHOR]

Lead-based mixed perovskite materials have emerged in the last couple of years as promising photovoltaic materials. Recently, it was shown that improved material stability can be achieved by incorporating small amounts of inorganic cations (Cs+ and Rb+), partially replacing the more common organic cations (e.g., methylammonium, MA, and formamidinium, FA). Especially, a mixed cation composition containing Rb+, Cs+, MA+, and FA+ was recently shown to have beneficial optoelectronic properties and was stable at elevated temperature. This work focuses on the composition of this material using synchrotron-based photoelectron spectroscopy. Different probing depths were considered by changing the photon energy of the X-ray source providing insights on the chemical composition and the chemical distribution near the surface of the samples. Perovskite materials containing two, three, or four monovalent cations were analyzed and compared. The presence of Cs and Rb was observed both at the sample surface and toward the bulk, and we found that in the presence of three or four cations, less unreacted PbI2 remains in the sample. Interestingly, Rb and Cs appear to act jointly resulting in a different cation depth profile compared to that of the triple counterparts. Our findings provide significant understanding of the intricate depth-dependent chemical composition in perovskite materials using the common practice of cation mixing. [ABSTRACT FROM AUTHOR]

A new D−π-A organicdye, LC-5, containing 4,9-dihydro-4,4,9,9-tetrahexyl-s-indaceno[1,2-b:5,6-b′]-dithiopheneas a novel π-conjugated spacer has beensynthesized and tested as a sensitizer in dye-sensitized solar cells(DSC). Volatile and ionic liquid electrolytes have been used in conjunctionwith the synthesized dye, and the electrolyte influence on the photovoltaicperformance of DSCs was investigated. A detailed investigation, includingtransient photocurrent/photovoltage decay measurements and electrochemicalimpedance spectroscopy data, provide important conclusions about theinfluence of electrolytes on the photovoltaic parameters. [ABSTRACT FROM AUTHOR]

Abstract: Colloidal quantum dot (CQD) photovoltaics combine low-cost solution processibility with quantum size-effect tunability to match absorption with the solar spectrum. Recent advances in CQD photovoltaics have led to 3.6% AM1.5 solar power conversion efficiencies. Here we report CQD photovoltaic devices on transparent conductive oxides and show that our devices rely on the establishment of a depletion region for field-driven charge transport and separation. The resultant depleted-heterojunction solar cells provide a 5.1% AM1.5 power conversion efficiency. The devices employ infrared-bandgap size-effect-tuned PbS colloidal quantum dots, enabling broadband harvesting of the solar spectrum. [Copyright &y& Elsevier]

Employing a mesoscopic titania photoanode whose bilayer structure was judiciously selected to fit the optoelectronic characteristics of the Ru-based heteroleptic complex Na-cis-Ru(4,4'-(5-hexyltiophen-2-yl)-2,2'-bipyridine)(4-carboxylic-acid-4'-carboxylate-2,2'-bipyridine)(thiocyanate)2, coded as C101, we investigated the effect of temperature for dye adsorption on the photovoltaic performance of dye-sensitized solar cells (DSCs). We found a significant efficiency enhancement upon lowering the temperature applied during the sensitizer uptake from solution. When the dye adsorption was performed at 4 °C, the photovoltaic performance parameters measured under standard reporting conditions (AM1.5 G sunlight at 1000 W/m2 intensity and 25 °C), i.e., the open circuit voltage (Voc), the short circuit photocurrent density (Jsc), the fill factor (FF), and consequently the power conversion efficiency (PCE), improved in comparison to cells stained at 20 and 60 °C. Results from electrochemical impedance spectroscopy (EIS) and attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) show that the self-assembled layer of C101 formed at lower temperature impairs the back-electron transfer from the TiO2 conduction band to the triiodide ions in the electrolyte more strongly than the film produced at 60 °C. Profiting from the favorable influence that the low-temperature dye uptake exerts on photovoltaic performance, we have realized DSCs showing a power conversion efficiency of 11.5%. [ABSTRACT FROM AUTHOR]

Abstract: A series of polyene–diphenylaniline based organic dyes (coded as D5, D7, D9 and D11) have been reported for the application in ionic liquid electrolyte based dye-sensitized solar cells. The effects of substitution of organic dyes on the photovoltaic performance have been investigated, which show addition of methoxy groups on the triphenylamine donor group increases short-circuit current, open-circuit voltage and photovoltaic performance. A power conversion efficiency of 6.5% under AM 1.5 sunlight at 100mW/cm2 has been obtained with D11 dye in combination with a binary ionic liquid electrolyte, which when subjected to accelerated testing under one sun light soaking at 60°C, the efficiency remained 90% of initial efficiency. [Copyright &y& Elsevier]

Abstract: A new ion-coordinating ruthenium polypyridyl sensitizer, NaRu(4-carboxylic acid-4′-carboxylate)(4,4′-bis[(triethyleneglycolmethylether) heptylether]-2,2′-bipyridine)(NCS)2 (coded as K68), has been synthesized and characterized by 1H NMR, FTIR, UV–Vis absorption and emission spectroscopy. A power conversion efficiency of 6.6% was obtained for dye-sensitized solar cells (DSCs) based on the K68 dye and a newly developed binary ionic liquid electrolyte containing 1-propyl-3-methyl-imidazolium iodide (PMII) and 1-ethyl-3-methyl-imidazolium tetracyanoborate (EMIB(CN)4). For a non-volatile organic solvent based electrolyte, a photovoltaic power conversion efficiency of 7.7% was obtained under simulated full sun light and exhibited a good thermal stability during the accelerated test under 80°C in the dark. Solid-state DSCs incorporating K68 also perform remarkably well, out-performing our previously best ruthenium complexes employed in this type of DSC. [Copyright &y& Elsevier]

Abstract: The optimization of interfacial charge transfer between the dye and the electrolyte is crucial to the design of dye-sensitized solar cells. In this paper, we address the combined use of an ionic liquid crystal electrolyte and amphiphilic ruthenium dyes in dye-sensitized solar cells. The solar cell with an amphiphilic ruthenium dye [Ru(H2dcbpy)(tdbpy)(NCS)2] (H2dcbpy=4,4′-dicarboxy-2,2′-bipyridine, tdbpy=4,4′-tridecyl-2,2′-bipyridine), exhibited a short-circuit photocurrent density of 9.1mA/cm2, an open-circuit voltage of 665mV and a fill factor of 0.58, corresponding to an overall conversion efficiency of 3.51%. We find that increasing dye alkyl chain length to octadecyl from tridecyl results in lower short-circuit photocurrent density and open-circuit voltage, and the suitable dyes for ionic liquid crystal electrolyte differed completely from those used in liquid and ionic liquid electrolyte cells. [Copyright &y& Elsevier]

A 7.4% power conversion efficiency at air mass (AM) 1.5 full sunlight was reached with a mesoscopic solar cell employing a new binary ionic liquid electrolyte composed of 1 -propyl-3-methylimidazolium iodide and 1 -ethyl-3-methylimidazolium tricyanomethanide in conjunction with the amphiphilic ruthenium complex NaRu(4-carboxylic acid-4'-carboxylate)(4,4'-dinonyl-2,2'-bipyridine)(NCS)2, coded as Z-9O7Na. Ultramicroelectrode voltammetric, nanosecond laser transient absorbance, and photovoltaic measurements show that a high iodide concentration is required for dye regeneration to compete efficiently with charge recombination. A surprisingly fast reductive quenching process is turned on in pure iodide melts. This channel is unproductive, explaining the lower photocurrents observed under these conditions. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the effectivity of coefficients (Cos) compared to photonics (Pt). It states that CoS was found out to an efficient electrocatalyst for triiodide reduction in dye-sensitized solar cells. The researchers suggest that the result of the study is a useful guide to performing chemical analysis.

Nanocrystalline dye-sensitized solar cells (DSCs) are attracting considerable academic and industrial interest as low-cost, high-efficiency alternatives to the conventional solid p-n junction photovoltaic devices. A record of 10.6% total power conversion efficiency has recently been reached using a liquid organic electrolyte based on the iodide/triiodide redox couple. The recentachievement of long-term thermal stability by molecular-scale interface engineering has undoubtedly injected new momentum into this field. However, the sealing of volatile electrolytes in large scale modules still remains a critical issue in view of the practical application.