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As electron transport layers (ETLs) in perovskite solar cells (PSCs), tin oxide (SnO2) possess high carrier mobilities with appropriate energy band alignment and high optical transmittance. Herein, SnO2 ETLs were fabricated by intermediate‐controlled chemical bath deposition (IC‐CBD) at ultralow temperature, where the chelating agent effectively altered the nucleation and growth process. Compared with conventional CBD, SnO2 ETLs fabricated by IC‐CBD had lower defects, smooth surface, good crystallinity, and remarkable interfacial contact with perovskite, resulting in good quality of perovskite, high photovoltaic performance (23.17 %), and enhanced stability of devices. [ABSTRACT FROM AUTHOR]

The photoelectric properties of nontoxic Sn‐based perovskite make it a promising alternative to toxic Pb‐based perovskite. It has superior photovoltaic performance in comparison to other Pb‐free counterparts. The facile oxidation of Sn2+ to Sn4+ presents a notable obstacle in the advancement of perovskite solar cells that utilize Sn, as it adversely affects their stability and performance. The study revealed the presence of a Sn4+ concentration on both the upper and lower surfaces of the perovskite layer. This discovery led to the adoption of a bi‐interface optimization approach. A thin layer of Sn metal was inserted at the two surfaces of the perovskite layer. The implementation of this intervention yielded a significant decrease in the levels of Sn4+ and trap densities. The power conversion efficiency of the device was achieved at 14.31 % through the optimization of carrier transportation. The device exhibited operational and long‐term stability. [ABSTRACT FROM AUTHOR]

The photoelectric properties of nontoxic Sn‐based perovskite make it a promising alternative to toxic Pb‐based perovskite. It has superior photovoltaic performance in comparison to other Pb‐free counterparts. The facile oxidation of Sn2+ to Sn4+ presents a notable obstacle in the advancement of perovskite solar cells that utilize Sn, as it adversely affects their stability and performance. The study revealed the presence of a Sn4+ concentration on both the upper and lower surfaces of the perovskite layer. This discovery led to the adoption of a bi‐interface optimization approach. A thin layer of Sn metal was inserted at the two surfaces of the perovskite layer. The implementation of this intervention yielded a significant decrease in the levels of Sn4+ and trap densities. The power conversion efficiency of the device was achieved at 14.31 % through the optimization of carrier transportation. The device exhibited operational and long‐term stability. [ABSTRACT FROM AUTHOR]

The performance of inverted perovskite solar cells (PSCs) is highly dependent on the surface properties of the hole‐transport layers (HTLs). Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most widely used HTLs due to its excellent properties. However, some drawbacks severely limit its application in PSCs. Herein, multifunctional bulk organic ammonium salts (BOASs) are deposited onto PEDOT:PSS films and used for interfacial modifications. The BOASs‐modified PEDOT:PSS has better energy‐level alignment with perovskite (PVK) than PEDOT:PSS, resulting in the suppressed voltage loss of PSCs. Depositing BOASs on top of the PSS isolates moisture to inhibit the ionization of sulfonic acid groups, which is beneficial to reduce the acidity and corrosiveness of PEDOT:PSS. In addition, the interfacial modification of BOASs can effectively enlarge the surface energy of PEDOT:PSS films and improve the morphology of the PVK layer. Therefore, the open‐circuit voltage and fill factor of the PSCs based on BOASs‐modified PEDOT:PSS are simultaneously increased to a maximum of 1.03 V and 73%, respectively, resulting in a champion device efficiency of 18.37%. The unencapsulated PSCs based on BOASs‐modified PEDOT:PSS remain more than 80% power conversion efficiency loss after 700 h of exposure to air. [ABSTRACT FROM AUTHOR]

The elimination of electron transport layers (ETLs) to fabricate ETL-free perovskite solar cells (PSCs) could save manufacturing costs and time. However, compared with PSCs based on the traditional architecture, ETL-free PSCs suffered low efficiency due to the device shunting and large energy barriers for carriers. Herein, a bifunctional interfacial modification material, 3-aminopropyl trimethoxy silane (APS), is selected and in situ grown on a transparent conducting oxide (TCO). On the one hand, the increased hydrophobicity of APS modified indium tin oxide (ITO) could improve the crystal growth of perovskites, resulting in larger grain sizes and reduced surface defects. On the other hand, the APS modification could improve the energy level alignment of ITO and the perovskite, leading to enhanced electron extraction and hole blocking. The PCE of the ETL-free PSCs based on APS modified ITO reached 19.09%, which was over 60% higher than that of ETL-free PSCs based on ITO. [ABSTRACT FROM AUTHOR]

Summary: The stability and toxicity of perovskite solar cells are still preventing full industrialization. Therefore, lead‐free all‐inorganic double perovskite materials have become the focus of research in recent years. Our group proposed a new narrow bandgap lead‐free double perovskite solar cell using a high‐quality Cs2PtI6 film. In this paper, for the purpose of exploring the trend in the bandgap and stability of the perovskite‐derived Cs2PtI6 substituted by halogen ions, we performed a first‐principles investigation based on density functional theory to study the structural and electronic properties of Cs2PtI6−yCly, Cs2PtI6−yBry, Cs2PtBr6−yCly (y = 0, 1, 2, 3, 4, 5, 6). The calculated structural parameters revealed a good mechanical stability for all these compounds, and the trend in the formation energy indicated that the substitution of I− with Cl− and Br− can significantly reduce the energy and improve the thermodynamic stability. Through a comparative analysis of the electronic properties of Cs2PtX6 (X = Cl, Br, I), we found that the substitutional doping of halogen ions can effectively adjust the bandgap and show an obvious change trend. The present study may demonstrate an effective theoretical guidance for preparing lead‐free all‐inorganic perovskite solar cell materials with appropriate bandgap and excellent stability. [ABSTRACT FROM AUTHOR]

Due to the low cost and strong hydrophobicity of carbon electrodes, carbon-based perovskite solar cells (C-PSCs) have drawn much attention. Copper(I) thiocyanate (CuSCN) is a favorable hole transport layer in perovskite solar cells (PSCs) because of its high chemical stability, high conductivity, and high hole mobility, but pinholes often appear during CuSCN film fabrication. In this work, organic ammonium salt, phenethylammonium iodide (PEAI), has been applied to modify the CuSCN film. The results indicated that PEAI not only eliminated the pinholes, but also passivated the perovskite film and enhanced the interfacial connection. Therefore, the power conversion efficiency (PCE) of C-PSCs increased by about 11%. The stability test showed that the C-PSCs, without any encapsulation, could maintain 70% of the initial efficiency after storage for 800 h in ambient air with 60%–70% relative humidity at room temperature. [ABSTRACT FROM AUTHOR]

Though perovskite solar cells (PSCs) or modules (PSMs) are being developed at an unprecedented speed, several obstacles remain to their commercialization. One of the difficult problems is the expensive and unstable Au and Ag counter electrode. Therefore, highly effective, stable, and low‐cost counter electrode materials should be explored. Among various counter electrode materials, carbon is one of the most promising substitutes for their rich sources, low cost, outstanding electrochemical performance, and diversified surface functions. This review summarizes recent achievements of carbon counter electrode materials, which included commercial carbon paste, carbon black, graphite, graphene, carbon nanotubes and their synthetic approaches, modifications, and structure‐function relationships. Moreover, large‐scale carbon counter electrode in PSCs or PSMs are specifically discussed. Hopefully, this recapitulative analysis will draw the attention of relevant researchers to re‐understand the importance of counter electrode and clarify what should be noticed to develop qualified counter electrode materials for PSCs or PSMs. [ABSTRACT FROM AUTHOR]

Power conversion efficiencies (PCEs) of up to 25.5 % have been reported for perovskite solar cells (PSCs). Thus, they have shown great potential for commercial applications. Therefore, simplifying technological process and reducing production costs have been a widespread concern among scientific and industrial communities. In this study, PSCs are prepared with the simplest device architecture (FTO/MAPbI3/carbon). A high‐quality perovskite film with few interface defects and good carrier transport is obtained by tuning the p‐n properties, matching energy levels, and enhancing carrier collection and transport. A PCE of 12.01 % is achieved, which is the best reported to date for this device structure. The device also shows excellent long‐term stability, owing to the elimination of charge transport layers and the usage of hydrophobic materials. This study provides a new approach to reduce production costs and simplify production of PSCs. [ABSTRACT FROM AUTHOR]

Two dimensional (2D) perovskite materials, are more stable than 3D perovskite materials, which could solve the stability issue of perovskite solar cells (PSCs). However, the photovoltaic conversion efficiency (PCE) of PSCs based on 2D perovskite materials was low, due to the high dielectric and quantum confinement of 2D perovskite. In this work, we propose a solvent-assisted method to prepare 2D perovskite films, where the solvent was distributed in a gradient. Therefore, the top-down crystallization process of 2D perovskite can be accurately controlled. The PCE of PSCs fabricated by the solvent-assisted method was enhanced by 48%, compared with the control device. For the packaged devices, the stability test demonstrated that 94% of the initial PCE was still maintained after 1500 hours of storage (25 °C, RH 40%). After carefully analyzing the photophysical process of the carriers in the PSCs based on 2D perovskite, the enhanced carrier transfer mechanism of the solvent-assisted method has been proposed. [ABSTRACT FROM AUTHOR]

Carbon‐based hole transport material (HTM)‐free CsPbI2Br perovskite solar cells (C‐PSCs) have garnered considerable attention due to their super thermal stability. The energy‐level mismatch between the CsPbI2Br perovskite and carbon electrodes, however, results in major energy loss and reduced power conversion efficiency (PCE) of C‐PSCs. Herein, 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIMBF4) is used to manage the energy level, reduce defect densities, and improve the interface quality between CsPbI2Br and carbon electrodes. Preliminary results demonstrate that the BMIMBF4 modifier can passivate the surface defects of the perovskite film and reduce the energy‐level mismatch between the CsPbI2Br layer and the carbon electrode. A PCE of 14.03% is achieved by introducing BMIMBF4 which is improved by 23% compared with the control device (11.37%). Moreover, stability—whether in the case of C‐PSCs or CsPbI2Br films—is also improved. [ABSTRACT FROM AUTHOR]

In the past decade, organic–inorganic hybrid perovskite solar cells (PSCs) have begun to be increasingly studied worldwide owing to the superior properties of perovskite material. However, some issues have delayed their commercialization, such as their long‐term stability, cost reduction, scale‐up ability, and efficiency. The introduction of sulfur to PSCs can relieve the above issues because sulfur can passivate interfacial trap states, suppress charge recombination, and inhibit ion migration, thereby enhancing the stability of PSCs. Furthermore, PbS bonds provide new channels for carrier extraction. Herein, the sulfur‐based compounds utilized in PSCs are summarized and classified according to their functions in the different layers of PSCs. The results indicate that these sulfur‐based compounds have efficiently promoted the commercialization of PSCs. It is hoped that this review can help others understand the intrinsic phenomena of sulfur‐based PSCs and motivate additional investigations. [ABSTRACT FROM AUTHOR]

Herein, it is reported that the stability of a halogenated perovskite (PVK) solar cell consisting of an fluorine‐doped tin oxide (FTO) substrate/TiO2/CH3NH3PbI3/N2,N2,N2′,N2′,N7,N7,N7′,N7′‐octakis(4‐methoxyphenyl)‐9,9′‐spirobi[9H‐fluorene]‐2,2′,7,7′‐tetramine/Ag/Au structure is improved by adding Sb‐xanthate to the PVK layer without large loss of efficiency. The Sb‐element‐rich layer is observed on top of the PVK layer. From the X‐ray photoelectron spectroscopy (XPS) study, it is concluded that an inorganic SbxOy passivation layer on the PVK layer is prepared by baking the solution of the Sb‐xanthate and the PVK precursor. The inorganic layer prevents moisture and oxygen from penetrating into the PVK layer. This article provides a new method to obtain a passivation layer on a PVK layer by baking a mixture solution in one step for improving solar cell stability. [ABSTRACT FROM AUTHOR]

A high‐performing inverted perovskite solar cell (PSC) always relies on the hole transporting layer (HTL) quality and its interfaces. This work investigates the impact of La incorporation within the NiOx matrix for defects passivation, thus leading to high charge extraction ability and stability without compromising its power conversion efficiency. In the presence of La, the La–NiOx quality is clearly improved; without the formation of pinholes. In addition, the inclusion of La alters the energy band alignment; consequently, enhancing the hole transportation and widening the Voc (>1 V), as compared to the pristine NiOx. The beneficial effect of La was further revealed through the photoluminescence measurement and density of states (DOS) analysis, in which trap states are passivated by La. More importantly, the perovskite solar cell, with La–NiOx as the HTL, exhibits 21 % enhancement in efficiency and a remarkable stability that is greater than that of pristine NiOx. This also unlocks an opportunity for commercialization. Inversion therapy: A high‐performing inverted perovskite solar cell (PSC) always relies on the hole transporting layer (HTL) quality and its interfaces. This study concerns the impact of lanthanum incorporation within the NiOx matrix for high conductivity, charge extraction ability, and stability without compromising its power conversion efficiency. [ABSTRACT FROM AUTHOR]

Trap states at the interface or in bulk perovskite materials critically influence perovskite solar cells performance and long‐term stability. Here, a strategy for efficiently passivating charge traps and mitigating interfacial recombination by SnO2 surface sulfur functionalization is reported, which utilizes xanthate decomposition on the SnO2 surface at low temperature. The results show that functionalized sulfur atoms can coordinate with under‐coordinated Pb2+ ions near the interface. After device fabrication under more than 60 % humidity in ambient air, the efficiency of methylammonium lead iodide (MAPbI3) perovskite solar cells based on sulfur‐functionalized SnO2 increased from 16.56 % to 18.41 % with suppressed hysteresis, which resulted from the accelerated interfacial charge transport kinetics and decreased traps in bulk perovskite by interfacial sulfur functionalization. Additionally, thermally stimulated current studies show the decreased trap density in the shallow trap area after interfacial sulfur functionalization. The interfacial sulfur functionalized solar cells without sealing also exhibited considerable retardation of solar cell degradation with only 10 % degradation after 70 days air storage. This work demonstrates a facile sulfur functionalization strategy by using xanthate decomposition on SnO2 surfaces to obtain highly efficient perovskite solar cells. Inorganic sulfur functionalization has been realized through xanthate annealing on a SnO2 substrate, facilitating electron transport and reducing trap density at the shallow area. The efficiency of the resulting perovskite device was increased significantly with enhanced long‐term stability upon interfacial sulfur functionalization. This method is a simple and highly efficient means of interfacial functionalization with enhanced stability by using inorganic atoms. [ABSTRACT FROM AUTHOR]

Abstract: Perovskite solar cells have attracted considerable attention owing to their easy and low‐cost solution manufacturing process with high power conversion efficiency. However, the fabrication process is usually performed inside a glovebox to avoid moisture, as organometallic halide perovskites are easily dissolved in water. In this study, we propose a one‐step fabrication of high‐quality MAPbI3 perovskite films in around 50 % relative humidity (RH) humid ambient air by using diethyl ether as an antisolvent and methanol as an additive into this antisolvent. Because of the presence of methanol, the water molecules can be efficiently removed from the gaps of the perovskite precursors and the perovskite film formation can be slightly controlled, leading to pinhole‐free and low roughness films. Concurrently, methanol can be used to tune the DMSO ratio in the intermediate perovskite phase to regulate perovskite formation. Planar solar cells fabricated by using this method exhibited the best efficiency of 16.4 % with a reduced current density–voltage hysteresis. This efficiency value is approximately 160 % higher than the devices fabrication by using only diethyl ether treatment. From the impedance measurement, it is also found that the recombination reaction is suppressed when the device is prepared with methanol additive in the antisolvent. This method presents a new path for controlling the growth and morphology of perovskite films in humid climates and laboratories with uncontrolled environments. [ABSTRACT FROM AUTHOR]

Transparent conductive oxide-less (TCO-less) dye-sensitized solar cells (DSSCs) have been fabricated and characterized using nanoporous TiO2-coated stainless steel metal mesh as flexible photoanode and cobalt bipyridyl complex (Co(bpy))-based one electron redox shuttle electrolyte. Attempts have been made towards enhancing the efficiency of TCO-less DSSCs to match with their TCO-based DSSC counterparts. It has been found that surface protection of metal mesh is highly required for enhancing the efficiency of TCO-less DSSCs specially using cobalt electrolytes as confirmed by dark current-voltage characteristics. Photocurrent action spectra clearly reveal that TCO-based DSSCs using (Co(bpy)) electrolyte exhibits photon harvesting (incident photon to current conversion efficiency (IPCE) 52%) in the 370-450 nm wavelength region as compared to photon harvesting at peak absorption of the dye (IPCE 56% at 550 nm), which is almost the same (IPCE 47%) in the 400-610 nm wavelength region for TCO-less DSSCs. Under similar experimental conditions, replacing indoline dye D-205 to porphyrin-based dye YD2-o-C8 led to the enhancement in the photoconversion efficiency from 3.33% to 4.84% under simulated solar irradiation. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells with sub-5 μm-thick Pt/SiC-P (1.79 at. % Pt), Pt/SiC-M (0.45 at. % Pt), and Pt/SiC-R (0.39 at. % Pt) counter electrode (CE) films fabricated by using three different processes produced power conversion efficiencies of 6.82, 7.64, and 7.04 % that reached 86.5, 97.0, and 89.3 %, respectively, of the level obtained by using a print-Pt CE (7.88 %). These materials can reduce the cost of CEs and solve challenges involving Pt. [ABSTRACT FROM AUTHOR]

Mesoporous-graphitic-carbon-supported HfO2 (HfO2-MGC) nanohybrids were synthesized by using a soft-template route. Characterization and a systematic investigation of the catalytic properties, stability, and catalytic mechanism were performed for HfO2-MGC counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). The new HfO2-MGC as a CE in DSSCs showed a surprisingly high efficiency of 7.75 % for the triiodide/iodide redox couple and 3.69 % for the disulfide/thiolate redox couple, greater than the Pt electrode in the corresponding electrolyte system, which opens up a possibility for its practical application. [ABSTRACT FROM AUTHOR]

TaO‐ and TaC‐based nanocomposites as novel and low‐cost counter electrodes (CEs) in dye‐sensitized solar cells (DSCs) show outstanding electrocatalytic activity and photovoltaic performance, superior to the Pt electrode. Based on the first‐principles density functional theory (DFT) calculations, I3 is chemisorbed onto the TaO surface as opposed to physical adsorption on the TaC surface. The TaO‐based composite is more efficient than the TaC‐based composite as a CE in DSCs. [ABSTRACT FROM AUTHOR]

Ta ‐ based compounds show Pt ‐ like behavior: Binary tantalum compounds as counter electrodes (CEs) in dye ‐ sENsitized solar cells (DSCs) demonstrate Pt ‐ like electrocatalytic activity and competitive photovoltaic performance, matching the performance of DSCs with Pt CEs. The first ‐ principle dENsity functional theory (DFT) calculations provide a strategy for understanding the relationship betweEN the electronic structure and the catalytic activity of CE catalysts in DSCs. [ABSTRACT FROM AUTHOR]

The article focuses on the dye-sensitized solar cells (DSCs) which features a moderate power conversion efficiency (PCE), low cost and plasticity. It mentions that the introduction of nanocrystalline semiconductor (metal oxide) mesoporous films is the major break through in the development of DSCs. It further mentions that titanium oxide-based DSCs performance level is low due to the fast recombination dynamics, low voltage value and poor adsorption capacity of sensitizer.

Titanium carbide (TiC) has been used as a counter electrode (CE) catalyst in place of Pt for triiodide reduction in dye-sensitized solar cells (DSCs). Its catalytic activity can be comparable to that of Pt. The effect of the thickness of the TiC layer on the performance of the DSCs was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and Tafel polarization measurements. We found that as the film thickness increased, the fill factor and short-circuit current density increased, which led to improved power-conversion efficiency. When the TiC film was thicker than 20 μm, however, no significant continuous improvement in the catalytic activity was observed. A high power-conversion efficiency of 6.46 % was obtained for the DSC by using a TiC CE at the optimized film thickness, a value similar to that obtained with a Pt CE. [ABSTRACT FROM AUTHOR]

Low-cost quantum-dot sensitized solar cells (QDSSCs) were fabricated by using the earth-abundant element SnS quantum dot, novel TiC counter electrodes, and the organic disulfide/thiolate (T2/T−) redox couple, and reached an efficiency of 1.03 %. QDSSCs based on I−/I3−, T2/T−, and S2−/S x2− redox couples were assembled to study the role of the redox couples in the regeneration of sensitizers. Charge-extraction results reveal the reasons for the difference in JSC in three QDSSCs based on I−/I3−, T2/T−, and S2−/S x2− redox couples. The catalytic selectivity of TiC and Pt towards T2/T− and I−/I3− redox couples was investigated using Tafel polarization and electrochemical impedance analysis. These results indicated that Pt and TiC show a similar catalytic selectivity for I−/I3−. However, TiC possesses better catalytic activity for T2/T− than for I−/I3−. These results indicate the great potential of transition metal carbide materials and organic redox couples used in QDSSCs. [ABSTRACT FROM AUTHOR]

The effects of the thickness and morphology of a Pt film coated on a counter electrode on the performance of a dye-sensitized solar cell (DSC) were investigated. Deposition of a Pt film ranging in thickness from 2 to 415 nm gradually decreases the sheet resistance of the counter electrode. No significant difference in the charge-transfer resistance at the electrolyte|counter electrode interface was observed for a Pt film thickness ranging from 25 to 415 nm. A high energy conversion efficiency of approximately 5% can be obtained for DSCs based on a counter electrode with a very thin Pt film of 2 nm, as well as with a 415-nm thick Pt film. These results are important for reducing production costs by reducing the required amount of expensive platinum. [Copyright &y& Elsevier]

An organic-medium screen-printing technique was developed for making porous TiO2 electrodes. The TiO2 pastes were prepared by mixing only 100% polyalkylene glycol and commercial nanocrystalline TiO2 powders. The obtained paste is highly printable and hard to evaporate during printing. The TiO2 electrodes have a very porous structure with large cavities. The dye-sensitized solar cell based on these meso-macroporous TiO2 electrodes exhibits high overall conversion efficiency of 4.3–5.8%, which is comparable to those of prepared by water or terpineol medium. [Copyright &y& Elsevier]

The ionic liquid N-butyl-N′-(4-pyridylheptyl)imidazolium bis(trifluoromethane)sulfonimide (BuPyIm-TFSI) was used as a dual-functional additive to improve the electrical properties of the hole-transporting material (HTM) for perovskite solar cells. BuPyIm-TFSI improved the conductivity of HTM and reduced the dark current of the solar cell simultaneously, thereby greatly increasing the power conversion efficiency. [ABSTRACT FROM AUTHOR]

Two transition metal tellurides, CoTe and NiTe2, were synthesized and for the first time employed as the counter electrodes (CEs) with high catalytic activity for reduction of I3− in dye-sensitized solar cells (DSCs). Using CoTe and NiTe2-based CEs, photoelectric conversion efficiencies (PCEs) of 6.92% and 7.21% were achieved for DSCs, respectively, comparable to that of 7.04% achieved when using a Pt-based CE. The results indicated that, serving as a CE in DSCs, telluride could be a cost-effective and efficient alternative to the noble metal Pt. [ABSTRACT FROM AUTHOR]

Porous chalcogels CoMoS4 and NiMoS4 made by a facile solution reaction displayed good electrocatalytic activity in the redox reaction of the I−/I3− shuttle. Dye-sensitized solar cells with these ternary compounds as counter electrodes (CEs) showed photovoltaic performance similar to the devices made with noble metal platinum CE (7.46%). [ABSTRACT FROM AUTHOR]

For the first time, nonstoichiometric WO2.72 was used as a counter electrode (CE) in dye-sensitized solar cells (DSSCs). Oxygen-vacancy-rich WO2.72 nanorod bundles with notable catalytic activity for triiodide and thiolate reduction were prepared in this study. The photovoltaic parameters of dye-sensitized solar cells (DSSCs) with WO2.72 nanorod bundles as CEs are superior compared with those of the WO3-based cells, and nearly the same as those of the precious metal Pt-based cells. In a non-corrosive organic redox couple, the performance of WO2.72 CEs is better than that of Pt and WO3 CEs in DSSCs. [ABSTRACT FROM AUTHOR]

Inorganic lead halide perovskites are attracting increasing attention due to their much better thermal stability than the organic–inorganic hybrid perovskite materials. Thus, the low power conversion efficiency (PCE) is a key issue for the inorganic lead halide perovskite solar cells (PSCs). This is mainly due to their wider bandgap and larger energy loss (Eloss) in the devices. Herein, for solving this issue, a dye molecule‐assisted engineering using the dye of 5,15‐bis(2,6‐dioctoxyphenyl)‐10‐(bis(4‐hexylphenyl)‐amino‐20‐4‐carboxyphenylethynyl)porphyrinato]zinc(II) (YD2‐o‐C8) is demonstrated. Results indicate that this molecule has a bifunctional effect, not only as a co‐sensitization layer for CsPbIBr2 with broader absorption spectrum but also reduces the Eloss by interface passivation. Specifically, the light absorption range of the photoactive layer is broadened from 600 to nearly 680 nm. At the same time, the interfacial charge recombination is highly reduced. After optimizing, the champion PCE is enhanced from 7.02% to 10.13%, and record‐high open‐circuit voltage (VOC) of 1.37 V and short‐circuit currents (JSC) of 12.05 mA cm−2 are achieved. This study opens a simple and efficient way to improve the efficiency of inorganic PSCs. [ABSTRACT FROM AUTHOR]

The photoelectric properties of nontoxic Sn‐based perovskite make it a promising alternative to toxic Pb‐based perovskite. It has superior photovoltaic performance in comparison to other Pb‐free counterparts. The facile oxidation of Sn2+ to Sn4+ presents a notable obstacle in the advancement of perovskite solar cells that utilize Sn, as it adversely affects their stability and performance. The study revealed the presence of a Sn4+ concentration on both the upper and lower surfaces of the perovskite layer. This discovery led to the adoption of a bi‐interface optimization approach. A thin layer of Sn metal was inserted at the two surfaces of the perovskite layer. The implementation of this intervention yielded a significant decrease in the levels of Sn4+ and trap densities. The power conversion efficiency of the device was achieved at 14.31 % through the optimization of carrier transportation. The device exhibited operational and long‐term stability. [ABSTRACT FROM AUTHOR]

The photoelectric properties of nontoxic Sn‐based perovskite make it a promising alternative to toxic Pb‐based perovskite. It has superior photovoltaic performance in comparison to other Pb‐free counterparts. The facile oxidation of Sn2+ to Sn4+ presents a notable obstacle in the advancement of perovskite solar cells that utilize Sn, as it adversely affects their stability and performance. The study revealed the presence of a Sn4+ concentration on both the upper and lower surfaces of the perovskite layer. This discovery led to the adoption of a bi‐interface optimization approach. A thin layer of Sn metal was inserted at the two surfaces of the perovskite layer. The implementation of this intervention yielded a significant decrease in the levels of Sn4+ and trap densities. The power conversion efficiency of the device was achieved at 14.31 % through the optimization of carrier transportation. The device exhibited operational and long‐term stability. [ABSTRACT FROM AUTHOR]

[Display omitted] All-inorganic perovskite materials (Typically: CsPbI 2 Br) have attracted enormous attention due to their illustrious thermal stability and appropriate bandgap, and their use in perovskite solar cells (PSCs) has been extensively investigated. However, the inevitable defects of the perovskite layer, energy level mismatch between perovskite and carbon electrodes, and the phase instability of CsPbI 2 Br limit the power conversion efficiency (PCE) and stability of carbon-based CsPbI 2 Br PSCs. Herein, we demonstrate a simple and effective strategy for regulating energy level, inhibiting carrier recombination, and delaying the degradation of perovskite by modifying the surface of CsPbI 2 Br with a new type of 2D perovskite Cs 2 PtI 6. The carbon-based CsPbI 2 Br PSCs achieve a higher PCE (13.69 %) than the control device (11.10 %). The excellent matching of the energy level and suppression of charge carrier recombination should be responsible for the improvement in efficiency. Furthermore, the excellent hydrophobic performance of Cs 2 PtI 6 enhances the moisture resistance of the device. This study provides a potential strategy for improving the performance and stability of all-inorganic CsPbI 2 Br PSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] The power conversion efficiency (PCE) of perovskite solar cells (PSCs) is already higher than those of other thin-film photovoltaic technologies, but the stability issue limits their applications. The introduction of sulfur-based compounds in PSCs could contribute to their stability. Herein, sulfur-based compounds have been embedded into each functional layer to stabilize carbon-based PSCs (C-PSCs). Results showed that the simultaneous introduction of sulfur-based compounds could decrease the trap states of perovskite film, enlarge the grain size of perovskite, and accelerate the charge transfer and extraction, leading to an improved performance. Comparing with the device without sulfide (10.77%), all sulfide C-PSCs obtained a PCE of 15.38%. The stability test showed much better resistance to humidity and thermal stress for all sulfide C-PSCs. They could retain 80% of initial PCE after aging about 700 h at relative humidity (RH) 45% ± 10% and 80 °C. [ABSTRACT FROM AUTHOR]

• Improvement interface quality between CsPbI 2 Br perovskite and carbon electrode by Delta-2:2-bis (1,3-dithiazole). • Achievement of high power conversion efficiency (13.78%) with the architecture ITO/SnO 2 /SnCl 2 /CsPbI 2 Br/Carbon. • Increasing the stability of carbon-based CsPbI2Br PSCs because of interface modification. All-inorganic perovskite materials, typically CsPbI 2 Br, have received widespread attention owing to their outstanding thermal stability than that of organic/inorganic hybrid counterparts. However, the power conversion efficiency (PCE) of CsPbI 2 Br perovskite solar cell (PSC) is far lower than its theoretical value. In this study, to further improve the PCE, a sulfur-rich small molecule material (delta-2:2-bis (1,3-dithiazole)), is used to modify the interface between CsPbI 2 Br and carbon electrode. Encouragingly, the carbon-based CsPbI 2 Br PSCs achieve a high PCE of 13.78% than the control of 10.40%, which is the best performance of carbon-based CsPbI 2 Br PSC among the literature report at present. The remarkable reduction of defect density and suppression recombination should be responsible for the PCE improvement. This work proposes a simple and effective strategy to enhance the efficiency of all-inorganic carbon-based CsPbI 2 Br PSCs. [ABSTRACT FROM AUTHOR]

As a hole transport materials (HTMs) and noble-metal free perovskite solar cells (PSCs), carbon-based PSCs (C-PSCs) have drawn much attention due to its low cost and excellent stability. The interfacial engineering, between perovskite and counter electrodes (CEs), played a crucial role in charge collection and affected the performance of C-PSCs. Herein, the systematic investigation of interfacial bridging carbon materials has been carried out to improve the interfacial contact. Results demonstrated that the morphology of interfacial bridging carbon materials played more important role than their energy band and conductivity, where carbon nanotube (CN) showed much better interfacial bridging effect and energy level alignment than other carbon materials. We achieved both the high power conversion efficiency (PCE) (15.09%) and stability in C-PSCs without HTMs due to the optimal interfacial bridging carbon material. It could retain 67% of their initial PCE after storing for 340 h under the rigorous environmental condition without any encapsulation (air atmosphere, 85 °C, 65% RH). [ABSTRACT FROM AUTHOR]

One of the major problems limits the applications of perovskite solar cells (PSCs) is the high cost of hole transporting materials (HTMs) and noble metallic electrodes. For HTMs and noble-metal-free PSCs, carbon materials have been utilized as counter electrodes (CEs). In this paper, four kinds of ultra-low-cost bio-carbon materials have been applied and compared in PSCs. Results showed that the photovoltaic performance of PSCs based on different bio-carbon CEs was determined by the interfacial connection, work function (WF), sheet resistance, crystallinity, and morphology of these bio-carbons. The high PCE (12.82%) of PSCs based on bio-carbon CEs has been achieved in current state-of-the-art. PSCs based on bio-carbon CEs was more stable than that of conventional devices, which could retain 87% of their initial PCE after storing for 2000 h in room temperature. Our work proposes a new pathway for the exploration of low-cost bio-carbon materials and could accelerate the applications of PSCs based on carbon electrode. Image 1 [ABSTRACT FROM AUTHOR]

SnO 2 has attracted considerable attention in perovskite solar cells (PSCs) due to its excellent optical and electrical properties. However, a poor surface morphology, specifically with the presence of pinholes after the annealing process, limits its application in PSCs. To overcome the drawback of tin oxide, lanthanum (La) is herein first to be doped into the SnO 2 layer, which is able to alleviate the SnO 2 crystal aggregation and produce full-coverage and a uniform film. In addition, La:SnO 2 can effectively reduce the band offset of the SnO 2 layer, which results in the high Voc of 1.11 V. Systematic analyses revealed that the La:SnO 2 layer enhances the electron extraction and suppresses charge recombination, leading to the power conversion efficiency (PCE) enhancement from 14.24% to 17.08%. Image 1 • La doped SnO 2 was ETL for planar PSCs with PCE of 17.08%. • La doping is a feasible strategy for improving the PCE. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have attracted a lot of attention from researchers as the most promising photovoltaic devices due to their outstanding power conversion efficiency (PCE) and low-cost. Although the PSC have reached a PCE over 25%, the interface between the perovskite and hole transport layer (HTL) still is a crucial factor limiting higher PCE and long-term stability. In this work, we choose an organic molecule Bis(trifluoromethyl)benzo amide (BTFZA) to passivate defects at the perovskite/HTL interface. Owing to a strong interaction with uncoordinated Pb2+, the BTFZA effectively passivated the surface defects, remarkably promoted carrier transportation. As a result, the perovskite device based on BTFZA surface modification showed a PCE increase of 16.4% over the control device. Especially, the fill factor (FF) and the open-circuit voltage (V OC) of the modified device increased significantly. In addition, the unencapsulated BTFZA-modified device maintains better PCE compared to the control device after aging for over 600 h in ambient air with extreme humidity and temperature conditions. Results suggested that the introduction of BTFZA is an effective way to regulate the surface of perovskite film aiming at highly efficient and stable perovskite solar cells. The successful application of surface passivation strategy can effectively improve the efficiency of perovskite solar cells. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract In recent years, attention is increasingly paid to developing layered two-dimensional perovskites due to their superior environmental stability compare with their three-dimensional analogues. However, two-dimensional perovskite based solar cells usually give unsatisfactory photovoltaic performance due to large numbers of defects in the process of crystallinity. Many groups investigate multiple approaches to improve the crystalline quality so far. Here, we systematically investigate the influence of temperature on two-dimensional (PEA) 2 (MA) 2 Pb 3 I 10 perovskite films crystallinity based on hot-casting and post-annealing. The crystallization of (PEA) 2 (MA) 2 Pb 3 I 10 in the case of hot-casting has better crystallinity than post-annealing and discover the thermal annealing and solvent-assisted mass transfer are very important in the process of crystallization based on two-dimensional perovskite. As a result, the devices obtain a highest power conversion efficiency of 5.57% at 100 °C (hot-casting) by optimizing heating temperature of the substrate and the hot-casting two-dimensional (PEA) 2 (MA) 2 Pb 3 I 10 films and devices display superior ambient stability. This work provides an important reference for further improve the crystallization of two-dimensional perovskite film. Highlights • 3D and 2D perovskites have different annealing procedures during crystallization. • Hot-casting preferred by 2D perovskite is assisted by both solvent and heating. • The influence of hot-casting and post-annealing on 2D perovskite is carried out. [ABSTRACT FROM AUTHOR]

The high cost of hole transporting materials (HTMs) and noble metallic electrodes limits the applications of perovskite solar cells (PSCs). Carbon materials, including carbon nanotube, graphene, and carbon paste, have been utilized for HTMs and noble-metal-free PSCs. Unlike other carbon materials, coal has extensive sources and lower price. A simple preparation process and an effective sandwich structure for the use of this material in PSCs were obtained by hot-pressing method. After the key parameters were adjusted, the power conversion efficiencies are 10.87% (0.3 cm2) and 8.72% (1 cm2). Therefore, devices with coal-based carbon electrodes have better stability than conventional devices. Our work proposes a promising future for the commercialization of low-cost and highly stable PSCs. Image 1 [ABSTRACT FROM AUTHOR]

Abstract TiO 2 has been extensively utilized as bottom electron transporting scaffold for perovskite solar cells (PSCs) but need for its high processing temperature (>450 °C) hinders its applicability for the flexible plastic substrates. Use of the low temperature processed ZnO is one of the probable solutions as electron transport layer (ETL) in PSCs owing to its high electron mobility. An amicable solution for the instability of the perovskite absorber layers fabricated on to ZnO leading resulting in to poor power conversion efficiency (PCE) and long-term stability is necessary for to harness the benefit of ZnO as ETL in PSCs. Herein, we modified the ZnO surface by spin-coating an ultrathin Nb 2 O 5 as surface passivation layer. In this work, both of the ZnO and Nb 2 O 5 were fabricated by spin coating and sintered at relatively lower temperature of 200 °C. Utilizing this Nb 2 O 5 surface passivated and low temperature processed ZnO as ETL, dramatically enhanced stability of perovskite film over 20 days under ambient condition has been clearly demonstrated. This bilayer of Nb 2 O 5 surface passivated ZnO scaffold used for fabrication of the planer heterojunction PSCs based on CH 3 NH 3 PbI 3 , led to the maximum PCE of 14.57% under simulated solar irradiation for an optimized ZnO thickness of 42 nm. Moreover, implication of the surface passivation of ZnO by Nb 2 O 5 leading to the formation of highly crystalline, stable and dense perovskite film has been probed by SEM and XRD investigations. Graphical abstract Image 1 Highlights • ZnO as an electron transport layer prepared at temperature lower than 200 °C. • ZnO surface passivation by Nb 2 O 5 solves the instability issue of perovskite films. • Nb 2 O 5 leads to the formation of highly crystalline, stable and dense perovskite film. • Perovskite films are stable over 20 days under ambient condition with best PCE of 14.58%. [ABSTRACT FROM AUTHOR]

Organolead halide perovskite is regarded as the most promising light-harvesting material for next-generation solar cells; however, the intrinsic instability and toxicity of lead are still of great concern. Bismuth is ecofriendly and has electronic properties similar to those of lead, which has gradually attracted interest for optoelectronic applications. However, the valence state of bismuth is different from that of lead, eliminating the possibility of replacing lead by bismuth in organolead halide perovskites. To address this matter, one feasible strategy is to construct B -site double perovskites by the combination of Bi 3+ and B + in 1:1 ratio. In this work, lead-free halide double perovskites of the form Cs 2 Na BX 6 ( B = Sb, Bi; X  = Cl, Br, I) were investigated by first-principles calculations. The electronic properties, optical absorption coefficients, and thermodynamic stability of these compounds were investigated to ascertain their potential application in solar energy conversion. The results provide theoretical support for the exploration of lead-free perovskite materials in potential optoelectronic applications. [ABSTRACT FROM AUTHOR]

Hybrid organic/inorganic perovskite solar cells (PVSCs) are promising alternatives to traditional photovoltaic devices because of their low cost, high power conversion efficiency, and simple production process. Therefore, achieving a low-temperature and high-efficiency procedure is necessary to realize the large-scale production of PVSCs. This study developed a facile low-temperature process (70 °C) for the synthesis of anatase TiO 2 thin films on the FTO substrate through an in situ growth method. The as-synthesized anatase TiO 2 thin films were applied on efficient compact layers of all low-temperature (sub-100 °C)-processed PVSCs. Under optimization, the achieved low-temperature PVSC device exhibited a champion conversion efficiency of up to 10.33%, with excellent repeatability and negligible hysteresis. Results revealed that fast electron extraction and transfer between perovskite and TiO 2 films and effective suppression of charge recombination are the main attributes for the excellent performance of the PVSC device. This work provides a new alternative to achieve low-temperature and high-efficiency photovoltaic devices. [ABSTRACT FROM AUTHOR]

Active composite layers of bismuth triiodide (BiI 3 ) and lead-free (CH 3 NH 3 ) 3 Bi 2 I 9 (MBI) perovskite were prepared using a simple chemical solution method under ambient conditions for thin-film solar cells. Results of X-ray diffraction and scanning electron microscopy indicated that the crystallization and surface morphologies of the composite films varied with perovskite contents. Multi-absorption was observed in the composite films due to the bandgap difference between BiI 3 and MBI perovskite. Moreover, band bending at the BiI 3 -perovskite interfaces resulted in the realignment of energy levels in the composite films, and this phenomenon was beneficial to the efficient injection of excited electrons from the active layers into the TiO 2 layers. Accordingly, due to the optimized crystallization and realigned energy level, when 20% of MBI perovskite was introduced into the active layers, the open-circuit voltage obviously increased from 0.44 V to 0.57 V in the (BiI 3 ) 0.8 (MBI) 0.2 composites solar cells, enhancing their power conversion efficiency by 67% compared with that in pure BiI 3 solar cell. This study developed a new route for designing more efficient lead-free solar cells. [ABSTRACT FROM AUTHOR]

Lead free double perovskites La 2 NiMnO 6 were first studied for potential application on solar cells. The rhombohedral and the monoclinic La 2 NiMnO 6 , with B -site of Ni 3+ /Mn 3+ , were respectively formed under different synthesizing conditions. The experimental results show that the monoclinic La 2 NiMnO 6 sample has a band gap of 1.4 eV and valence band of −5.8 eV, on the other hand, the respective values for rhombohedral sample are 1.2 eV and −5.7 eV. The density function theory calculation demonstrates that the calculated band gap for the monoclinic La 2 NiMnO 6 is larger than that for the rhombohedral one. However, the electronic structures for these La 2 NiMnO 6 are found very similar to each other. Our combined experimental and theoretical studies indicate that, from the aspects of band gaps and energy levels, double perovskite La 2 NiMnO 6 of monoclinic phase could be a better candidate than that of rhombohedral phase for light harvesting. [ABSTRACT FROM AUTHOR]