The fabrication of large-area, high-efficiency perovskite solar cell module (PSM) represents a pivotal stage in the industrialization of perovskite solar cells (PSCs). Leveraging volatile solvents within perovskite precursors is a streamlined approach which offers distinct advantages in the industrialization trajectory of PSCs, but often exhibits accelerated crystallization kinetics, diminutive grain dimensions and elevated defect densities within the films, consequently compromising device efficiency and stability. This study devised a volatile solvent system comprising methylamine/acetonitrile (MA/ACN) for the production of MAPbI₃ perovskite solar cells/module. Incorporation of an optimal quantity of PbCl₂ into the perovskite precursor solution served to retard crystallization kinetics and passivate grain boundary imperfections. Notably, small-area device fabricated via this methodology demonstrated a peak photovoltaic conversion efficiency (PCE) of 21.21%, alongside enhanced operational stability. Furthermore, PSM engineered through this approach achieved a PCE of 18.89%. This study presents a novel paradigm for advancing the large-scale industrial manufacturing of PSCs.

Carbon-based perovskite solar cells (C-PSCs) have attracted significant interest for their advantages of high photoelectric conversion efficiency (PCE), long-term stability and low cost, showing superiority in commercialization of perovskite solar cells (PSCs). However, the promoting effect of PbTiO₃ modification and polarization treatment on C-PSCs photovoltaic performance by in-situ generation of PbTiO₃ on a dense electron transport layer of TiO₂ (c-TiO₂) is still unknow.. It was found that the PbTiO₃ formed after reaction for 30 s could effectively restrict the sharp increase in resistance of the electron transport layer, and substantially reduced the carrier accumulation at the interface to 29.7%, greatly improving the carrier separation ability. In addition, the carrier accumulation was further reduced to 6.78% through polarizing the c-TiO₂/PbTiO₃ layer, so that PSCs displayed 0.93 V of open circuit voltage (V_oc), 14.83 mA/cm² of short circuit current density (J_sc), 51.16% of fill factor (FF), and 7.11% of PCE. This work comprehensively reports the methods of PbTiO₃ modification and polarization treatment, proposes a research strategy to improve the performance of C-PSCs, reveals the intrinsic mechanism for optimizing carrier transport performance, and provides a way for developing high-efficiency, low-cost and long-life commercial PSCs.

Recently, perovskite solar cells have developed marvelously of which power conversion efficiency (PCE) achieved 26.1%, but the mechanical bending and environmental stability of flexible perovskite solar cells (F-PSCs) have remained major obstacles to their commercialization. In this study, the quality and crystallization of perovskite thin films were enhanced by adding agarose (AG). The interaction mechanism, PCE, mechanical bending and environmental stability of the assembled F-PSCs were investigated. It was found that the perovskite films modified by the optimal concentration of AG (3 mmol/L) exhibited denser and smoother morphology, higher crystallinity and absorbance, the lowest defect state density, and lower charge transfer resistance of 2191 Ω. Based on the optimal photoelectric properties, PCE increased from 15.17% to 17.30%. TiO₂ nanoparticles (0.75 mmol/L) were further introduced to form a synergistic interaction with AG (3 mmol/L), which provided a rigid backbone structure, and thus enhanced the mechanical and environmental stability of perovskite layers. After 1500 cycles of bending (3 mm in radius), the AG/TiO₂ co-modified F-PSCs maintained 84.73% of initial PCE, much higher than the blank device (9.32%). After 49 d in the air, the optimal F-PSCs still maintained 83.27% of initial PCE, superior than the blank device (62.21%). This work provides possibility for preparing highly efficient and stable F-PSCs.

Tin dioxide (SnO₂) is widely used in perovskite solar cell (PSC) as an electron transport material due to its high transmittance, high electron mobility, good UV stability, and low-temperature processing. However, SnO₂ electron transport layer prepared from commercial colloidal solution still faces some challenges such as easy agglomeration, defects, and energy level mismatch, limiting its performance and stability. This study improved the quality of SnO₂ films by introducing a polymer chitin nanofiber (1,2-dibenzoyloxyphenylchitin, DC) into the SnO₂ precursor solution, and systematically studied the effect of DC on the precursor solution, film and device performance. Experimental results showed that DC additive could effectively inhibit the agglomeration of SnO₂ nanoparticles, ensuring a more homogeneous dispersion in the precursor solution. The improved SnO₂ films had smaller roughness and could be better wetted by perovskite solution, which is beneficial to closer contact with the perovskite layer. Simultaneously, the oxygen vacancy defects in the SnO₂ films were effectively passivated, and the proportion of defects was reduced to 30%, further improving the quality of the films. Based on the improved energy level matching between the SnO₂ electron transport layer and the perovskite layer, the carrier extraction and transport performance was optimized. The performance of DC-modified PSC was significantly improved, and the photoelectric conversion efficiency of the optimal device reached 19.11%. This work not only overcomes the agglomeration problem of the SnO₂ electron transport layer during the preparation process, but also provides theoretical guidance and method for improving the performance of perovskite solar cells.

As renewable and sustainable clean energy, solar energy has the potential to address current energy shortage and reduce environmental pollution caused by fossil fuels consumption. In recent years, the third-generation thin-film solar cells, such as dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs), have attracted widespread attention due to their low cost, abundant materials, and high photoelectric performance. However, these devices still face challenges in terms of charge transfer efficiency and operational stability for their commercialization. Two-dimensional (2D) MXene materials have emerged as promising candidates for improving the performance of thin-film solar cells due to their unique properties, including high specific surface area, rich surface functional groups, high conductivity, tunable work function, and hydrophilicity. This review summarizes the recent research progress of 2D MXene materials applied in new thin-film solar cells, focusing on the reaction mechanism that enhances the photoelectric performance of solar cells. Strategies such as using 2D MXene materials as additives for the perovskite layer and charge transport layer in PSCs, modifying the photoanode in DSSCs, and preparing varous electrodes, can effectively improve light absorption efficiency, carrier mobility, and charge extraction capability of the devices by adjusting band alignment, reducing work function, broadening the light absorption range, and creating a “pillar support effect”. As a result, the photoelectric performance and stability of the devices are enhanced. In conclusion, the perspectives highlights the current research progress and challenge faced by 2D MXene materials in novel thin-film solar cells.

Recently, organic-inorganic hybrid perovskite solar cells have demonstrated a broad commercial prospect due to their high photoelectric conversion efficiency (PCE) and low fabricating costs. During the past decades, the highest reported PCE of small-area (<1 cm²) perovskite solar cells (PSCs) rose to 26.10%, and those of large-area (1-10 cm²), mini-module level (10-800 cm²) and module level (>800 cm²) PSCs increased to 24.35%, 22.40% and 18.60%, respectively. The performance of PSCs decreases dramatically with the area increasing due to limitation of the deposition method and the poor quality of large-area perovskite films. Spin-coating method is not suitable for actual industrial production, while the scalable deposition methods including blade-coating and slot-die coating still face the difficulty of precisely controlling nucleation and crystallization of the perovskite films with large area. This review summarized preparation methods of large-area perovskite films, and discussed the film-forming mechanism and strategies for high-quality perovskite films. Finally, relevant outlooks on technologies and applications for large-area PSCs with high performances and stabilities were analyzed. This review is expected to provide insights on the research of large-area PSCs with high performance.

Hysteresis effect greatly impacted performance and stability of perovskite solar cells. Ion migration and the resulting accumulation of interface ions were widely recognized as the most important origins. In this study, upconversion luminescent nanoparticles (UCNP) were used to modify the interface of the electron transport layer/perovskite active layer and the intrinsic perovskite active layer, and the effects of UCNP on the morphology, structure, spectral/optoelectronic properties, and ion migration kinetics of perovskite were systematically explored. The results indicated that the device with UCNP modified perovskite active layer has the best photoelectric conversion efficiency (PCE, 16.27%) and significantly improves the hysteresis factor (HF, 0.05). Furthermore, circuit switching transient optoelectronic technology was employed to investigate the ion migration kinetics without interference from photo-generated carriers, revealing the dual role of UCNP in suppressing ion migration and accumulation during the optoelectronic conversion process of perovskite solar cells. On the one hand, UCNP formed barrier layers that hinder ion accumulation. On the other hand, UCNP infiltrated into grain boundaries of perovskite phase during annealing, hindering ion migration and reducing the recovery voltage from 0.43 V to 0.28 V. The mechanism of carriers and ions interaction was explained based on the polarization-induced trap state model to declare the process of UCNP suppressing the hysteresis of perovskite photovoltaic devices. This work provides effective solution for regulating the hysteresis of perovskite solar cells.

Organic-inorganic hybrid perovskite solar cells (PSCs) have attracted widespread attention due to their high power conversion efficiency (PCE) and low manufacturing cost. Although the certified PCE has reached 25.8%, the stability of PSCs under high temperature, high humidity, and continuous light exposure is still significantly inferior to that of traditional cells, which hinders their commercialization. Developing and applying highly stable inorganic hole transport materials (HTMs) is currently one of the effective methods to solve the photo-thermal stability of devices, which can effectively shield water and oxygen from corroding the perovskite absorption layer, thereby avoiding the formation of ion migration channels. This paper outlines the approximate classification and photoelectric properties of inorganic HTMs, introduces relevant research progress, summarizes performance optimization strategies for inorganic HTMs devices, including element doping, additive engineering, and interface engineering, and finally prospects the future development directions. It is necessary to further study the microstructure of inorganic HTMs and their relationship with the performance of PSCs to achieve more efficient and stable PSCs.

Power conversion efficiency of single-junction solar cells is fundamentally limited by the Shockley- Queisser (S-Q) limit. The most promising practical technology to break through the S-Q limit is to use two-terminal tandem structure which can simultaneously solve the problems, spectral mismatch and thermal relaxation energy loss, in single-junction devices. As one of the important components of the interconnecting layer, the recombination layer in the two-terminal tandem solar cells can provide recombination sites for electrons and holes extracted from the electron transporting layer and the hole transporting layer, avoiding the open-circuit voltage loss caused by charge accumulation and promoting the current flow of tandem solar cells. The recombination layer is considered as one of the key factors of achieving high-performance tandem devices. The ideal recombination layer should possess high conductivity to improve the charge recombination rate, high optical transmittance to ensure effective light absorption of the rear subcells, good chemical stability to reduce the damage caused by the solvent, and low preparation cost to promote the commercial production process. At present, a variety of materials have been used in two-terminal tandem solar cells, such as thin metals, transparent conductive oxides, conductive polymers, graphene oxide, etc., which play an important role in perovskite-perovskite, perovskite-organic, and perovskite-silicon two terminal tandem devices. In this review, the research progress of recombination layers in different types of tandem solar cells is summarized, together with types, design principles, preparation processes, and their advantages and disadvantages. Meanwhile, problems and challenges of the current recombination layers are proposed, which provides a useful reference for the design of high-performance tandem cells.

In recent years, organic-inorganic hybrid perovskite solar cells have received a lot of attention for their excellent performance and low manufacturing cost. However, the toxicity of lead in organic-inorganic hybrid perovskite solar cells and instability inhibits its further commercialization. Double perovskite Cs₂AgBiBr₆ possess excellent stability, low toxicity, long carrier lifetime, and small effective carrier mass, and is considered as a promising photovoltaic material. It has been applied in solar cells and displayed superior performance. However, the power conversion efficiency of Cs₂AgBiBr₆ perovskite solar cell still lags behind organic-inorganic hybrid perovskite solar cells, and its development faces various challenges. This review firstly introduces the crystal structure and the structural parameters such as tolerance factor of Cs₂AgBiBr₆. And then, the progress of thin film preparation technologies such as solution processing method, anti-solvent assisted film forming method, vapor deposition processing method, vacuum-assisted film forming method, spray-coating method are summarized, and the advantages and disadvantages of various preparation technologies are discussed. The performance optimization strategies of Cs₂AgBiBr₆ perovskite solar cells are analyzed from three aspects: element doping, additive engineering, and interface engineering (interface energy level matching and interface defect passivation), and the research progress in recent years is reviewed. Finally, the challenges faced by Cs₂AgBiBr₆ perovskite solar cells are pointed out, and future research directions are prospected from three aspects: precursor solvent engineering, bandgap engineering, and device degradation mechanism.

Hybrid organic-inorganic perovskite solar cells (PSCs) have attracted global attention as one of the most promising photovoltaic materials due to their high efficiency, low energy consumption and low cost. However, non-radiative recombination caused by interface defects severely inhibits the performance of PSCs. To solve this critical issue, the particle size of nickel oxide (NiO_x) hole transport layer was reduced to improve the particle size uniformity and achieve efficient hole transport. Furthermore, the antisolvent acting time of the perovskite film was optimized to reduce the interfacial non-radiative recombination and interfacial defect. As a result, the crystalline quality is improved and power conversion efficiency (PCE) of the perovskite solar cells increase from 10.11% to 18.37%. Kelvin probe atomic force microscopy (KPFM) study shows that the contact potential difference (CPD) of the optimized perovskite film in the illumination condition increases by 120.39 mV compared with that under the dark condition. Analysis by piezoelectric atomic force microscopy (PFM) reveals that the ferroelectric polarization of the optimized interfacial perovskite films hardly changes from illumination to dark states, indicating that reducing interfacial defects can decrease the hysteresis effect of the PSCs. It is concluded that optimizing the NiO_x hole transport layer and improving the quality of perovskite film can reduce the interface defects, the non-radiative recombination and the hysteresis effect, and improve PCE of perovskite solar cells.

Perovskite solar cells (PSCs) are developing rapidly and their power conversion efficiency (PCE) has been repeatedly refreshed, but their long-term stability still needs to be improved. At present, most of the preparation of high-efficiency PSCs is completed in the inert gas, with high cost and limited operating space, which is not conducive to its industrial application. Here, perovskite solar cells with mixed cation, displaying ultra-long stability, were successfully prepared in the air. Effects of A-site cation doping on the microstructure, optoelectronic properties and stability of the perovskite were systematically investigated. The experimental results show that FA⁺ and Cs⁺ co-doping improves the quality of perovskite films, modulates the energy level arrangement of perovskite/SnO₂, suppresses carrier complexation, and significantly improves the PCE, long-term, wet and thermal stability of the cell. The optimal PCE of Cs_0.05MA_0.35FA_0.6PbI₃ cells is 19.34%, maintaining 85% of the initial efficiency after reserving for 242 d in dark environment at (20±5) ℃ and <5% relative humidity. In contrast, the PCE of the MAPbI₃ cell decreased to 30% of the initial value after reserving for 112 d under the same test conditions. FA⁺ and Cs⁺ co-doping also significantly improved the thermal and moisture resistance of the cells. Cs_0.05MA_0.35FA_0.6PbI₃ PSCs remain 99% and 84% of initial PCE after aging for 96 h at (85±5) ℃ and 20%-30% relative humidity, (20±5) ℃ and 80%-90% relative humidity in the dark, respectively. In contrast, PCEs of MAPbI₃ PSCs under the same conditions remain only 70% and 56%. This study provides a reference for the preparation of highly efficient and ultra-long stable mixed cation solar cells in the air.

Organic-inorganic hybrid perovskite is an ideal light absorption material due to its high light absorption coefficient, adjustable band gap and bipolar charge conduction characteristics. However, perovskite thin films prepared by solution method possess various defects in the surface and interface, which inhibit carrier transport and trigger recombination. In this study, a multifunctional amino acid derivative, 9-fluorenylmethoxycarbonyl- L-phenylalanine-L-phenylalanine (Fmoc-FF-OH), was selected as an additive to reduce defects of perovskite film and to inhibit carrier recombination at grain boundaries. When the concentration of Fmoc-FF-OH is 0.6 g·L^-1, the particle size of the perovskite thin film increases from 138 to 210 nm, and the defect state density decreases from 2.46×10¹⁵ to 2.17×10¹⁵ cm^-3. Perovskite solar cells also exhibit optimal performance with open circuit voltage increasing from 1.05 to 1.10 V, and photoelectric conversion efficiency (PCE) improved from 15.50% to 17.44%. After stability test for 220 h, the photoelectric conversion efficiency of the device can still maintain 71% of the initial.

With a bandgap of 1.1-1.4 eV, Sn/Pb mixed halide perovskites are ideal materials for single-junction solar cells to reach the power conversion efficiencies (PCEs) limit of Shockley-Queisser (S-Q) theory. Their chemical composition gradient in the vertical direction of the perovskite films affect the transport and separation of carriers by changing the energy band structures. Therefore, it is very important to control the crystallization process of tin-lead mixed perovskite thin films. In this work, it was found that different vertical composition gradients were formed when tin-lead mixed perovskites were prepared with different amounts of the anti-solvent. Larger amounts of anti-solvent was contributed to higher lead content on the film surface. The vertical composition gradient of tin-lead mixed perovskite could be regulated by adjusting the solvent composition, among which increasing V(DMSO):V(DMF) in the solvent could form a vertical composition gradient with a lead-rich bottom and a tin-rich surface. When V(DMSO):V(DMF) in lead-based precursor solutions was optimized to 1 : 2, compared with the control group of 1 : 4, open circuit voltage of the device under standard light conditions increased from 0.725 to 0.769 V, short circuit current density from 30.95 to 31.65 mA·cm^-2, and PCE from 16.22% to nearly 18%. Numerical simulations using SCAPS further proved the necessity of forming a vertical composition gradient. When the bottom of the perovskite film is rich in lead and the top is rich in tin, the recombination of carriers in the hole transport layer interface region is reduced, which can improve the device’s performance.

Carbon-based perovskite solar cells (C-PSCs) play an important role in industrialization research due to their stability and low cost. In this work, high-quality NiO_x mesoporous layer was selected as a hole transport layer (HTL) based on MAPbI₃ material to enhance the performance of C-PSCs. The effect of preparation methods of the NiO_x mesoporous layer on the solar cell performance and the optimum thickness of the NiO_x mesoporous layer were investigated. It was found that mesoporous layers prepared by screen-printing process with well-distributed pores facilitated the filling of perovskite (PVK) precursor solution in the underlayer mesoporous scaffold. Finally, an HTL-contained perovskite solar cell with high efficiency and almost negligible hysteresis was achieved, possessing an open-circuit voltage (V_OC) of 910 mV, a power conversion efficiency (PCE) of 14.63%, and certified efficiency reached 14.88%. Moreover, PCE of the solar cell displayed outstanding stability after being stored in air for nearly 900 h.

Solution-processed perovskite films usually contain a large quantity of grain boundaries, which decrease the film crystalline quality and introduce severe defect recombination, hindering performance of the devices based on them. Therefore, preparation of high-quality films to achieve high power conversion efficiencies remains a great challenge for perovskite solar cells. Due to high abilities of self-assembly and morphology-tuning for liquid crystal molecules, a single-molecule liquid crystal 4-cyano-4′-pentyl biphenyl (5CB) was employed as additive in CH(NH₂)₂PbI₃ (FAPbI₃) precursor solution to increase the perovskite grain size and decrease the grain boundaries. In addition, the cyano group in 5CB passivates the uncoordinated Pb²⁺ in the perovskite films, which reduces the trap density concentration and inhibits the nonradiative recombination. The resulting perovskite solar cells with 0.2 mg/mL 5CB in the precursor achieve an efficient power conversion efficiency of 21.27% with an open circuit voltage of 1.086 V, a current density of 24.17 mA/cm², and a fill factor of 80.96%. In conclusion, introducing single-molecule liquid crystal as additive is a facile and efficient strategy for improving the performance of FAPbI₃ solar cells.

Perovskite solar cells (PSCs) with structure of TiO₂/ZrO₂/carbon triple-layer are attractive recently because of their inexpensive raw materials, scalable fabrication process, and outstanding stability. But little progress has been made in the low temperature fabrication of TiO₂/ZrO₂/carbon triple-layer structured PSCs. A major reason is that it is rather difficult to construct the ZrO₂ spacer layer at low temperature. Herein, we report a facile low-temperature spray-coating method to prepare effective ZrO₂ spacer layer in TiO₂/ZrO₂/carbon triple-layer PSCs using urea to tune the porosity. After optimizing the amount of urea and the thickness of zirconia to 1100 nm, power conversion efficiencies (PCE) of 14.7% for a single cell and 10.8% for a module with 5 cells connected in series (5×0.9 cm× 2.5 cm) were achieved. Furthermore, the PSCs could be stable for 200 d at constant temperature (25 ℃) and humidity (40%). With this spray coating method, the zirconia layer on flexible substrate can endure 50 times of bending without any cracking. Compared to the conventional screen-printing method of ZrO₂ spacer layer, the spray-coating alternative developed in this work shows advantages of more convenient to process, preparation under lower temperature, and compatibility to flexible substrate.

Density functional theory calculations play an important role in the study of defects in halide perovskites. Although the traditional semi-local functionals (such as PBE) can obtain the band gaps close to the experiments, they fail to accurately describe the positions of the band edges. Utilizing more accurate hybrid functionals combined with the spin-orbit coupling (SOC) effect with full structure relaxation is considered to be necessary for the prediction of defect properties. There are two types of hybrid functionals in the literature, namely the screened HSE and the unscreened PBE0. In this study, taking the orthorhombic phase CsPbI₃ as an example, these methods were compared for the calculation of defect properties. The results show that there is no obvious difference between two methods for bulk properties, but qualitative differences appear for the defect properties. Most of the shallow-level defects predicted in the HSE calculations become deep-level defects in the PBE0 calculations. Meanwhile, there are qualitative differences between the defect transition levels and the Kohn-Sham levels. The origin of above differences lies in the fact that the Hartree-Fock exchange potential has long-range interaction. Therefore, in unscreened hybrid functionals, such as PBE0, it is more difficult to obtain convergent results with a manageable supercell size. In contrast, HSE exhibits a screening effect on the Hartree-Fock exchange potential and can obtain accurate defect energy levels using relatively small supercell sizes. Therefore, all results here demonstrate that the HSE hybrid functional owns a significant advantage in dealing with this problem even though a large Hartree-Fock mixing parameter (about 0.43) is needed.

Solar thermal radiant energy is abundant in storage and pollution-free, and is one of the most competitive clean energies in the future. In recent years, halide perovskite quantum dots (PQDs) are widely used in solar cells and luminescent concentrator solar cells due to their excellent photoelectric properties and unique advantages such as quantum confinement effect and solution processing, and possess vast application prospects, but they are still facing many challenges in future commercial applications. In this review, optimization strategies for improving cell performance are emphatically summarized combined with the domestic and foreign research progress in the field of PQD solar cells. The application of PQDs in luminescent concentrator cells is introduced. Finally, the current challenges in this field are elaborated, and its development trends are prospected. This review provides some ideas for the design and development of the photovoltaic technology in the future.

Defects at the surface and grain boundary of the three-dimensional (3D) organic-inorganic metal halide perovskite film incline to cause non-radiative recombination of charge carriers and accelerate decomposition of 3D perovskite, in turn deteriorating the power conversion efficiency (PCE) and stability of the perovskite solar cells (PSCs). In this study, the organic 4-chlorobenzylamine cation was applied to react with 3D perovskite and the residual PbI₂ to in-situ form a two-dimensional (2D) perovskite top layer, which can passivate the surface and grain boundary defects of the 3D perovskite film, and improve the surface hydrophobicity. Based on this strategy, 2D/3D-PSCs with higher PCE and better stability were successfully obtained. Their structure, morphology photoelectric propery and stability of PSCs were systematically studied. All results show that 2D/3D-PSCs achieve PCEs up to 20.88%, much higher than that of 18.70% for the 3D-PSCs. In addition, 2D/3D-PSCs can maintain 82% of the initial PCE after 200 h continuous operation under 1-sun illumination in N₂ atmosphere, exhibiting excellent stability.

Printable perovskite solar cells employ a device structure for which the organic-inorganic perovskite absorber is hosted by an inorganic mesoporous scaffold. Its advantages include simple fabrication process, low material cost and relatively high stability. However, it is challenging to homogeneously deposit high-quality perovskite crystals on the mesoporous scaffold. Herein, by incorporating lead acetate (Pb(Ac)₂) in the typical perovskite precursor, methylamine lead iodine (MAPbI₃), the crystal growth and pore-filling of the perovskite crystals in the mesoporous scaffold is improved by facilitating the crystal nucleation. Meanwhile, Ac^- and MA⁺ form MAAc which releases during thermal annealing process, resulting in excess PbI₂ in the perovskite layer which passivates the grain boundaries. By incorporating 1% molar ratio of Pb(Ac)₂ in the perovskite precursor, a power conversion efficiency of 15.42% is obtained for printable perovskite solar cells. This indicates that it is feasible to enhance the performance of printable perovskite solar cells by employing additives to tune the crystallization of the perovskite absorbers.

The investigation of defects in perovskite crystals is essential to promote the development of perovskite solar cells. The defects result in non-radiative recombination as well as the deterioration of device stability. To reduce the impact of material defects on photovoltaic performance, it is necessary to deeply understand the types of perovskite film defects and the routes of suppression methods. According to electronic characteristics, defects can be divided into electron-rich and electron-deficient defects. Based on Lewis acid-base theory, electron-rich defects can be passivated by Lewis acid, and electron-deficient defects can be passivated by Lewis base or ionic liquids. These passivation additives can be added during the formation of perovskite film, or used to post-treat the surface of the films. This review summarized the defect passivation cases reported in recent years to visually present design strategies of additives and the effects of defect passivation on photovoltaic performance. Finally, developing multi-functional passivators, large-area passivation strategy and advanced charge transport layer were proposed for future perspective. This review is expected to promote the development of perovskite solar cells in the future.

Semitransparent photovoltaics (STPV) is a promising solar energy harvesting technology because it can be integrated to harness huge sun-facing areas of modern buildings for electricity generation. Its thermodynamic efficiency limits are of fundamental interest. This work extended the analyses from neutral STPV for building windows to those installed on the surface of colored building envelops according to the principle of detailed balance. Results show that the efficiency limit of STPV for blue building envelops is as high as 28.3%, which represents a 10% absolute enhancement compared to the neutral STPV for building windows (18.1%). These results demonstrate that STPV can be integrated into both windows and envelops of modern buildings, which has the potential to offset the low density of solar energy. This work provides guidelines on the selection and the development of active materials for STPV.