JIALINGBO

This study examines the extensive metal halide perovskite device data compiled in the Perovskite Database, comprising more than 40,000 devices. The collective efforts of over a decade of perovskite research enable the identification of overarching trends in higher bandgap devices. Increasing efficiency loss with bandgap is attributed to mismatched transport materials, compositional inhomogeneity, and suboptimal optoelectronic absorber quality.

Abstract

Metal halide perovskites (MHPs) have become a widely studied class of semiconductors for various optoelectronic devices. The possibility to tune their bandgap (E _g) over a broad spectral range from 1.2 eV to 3 eV by compositional engineering makes them particularly attractive for light emitting devices and multi-junction solar cells. In this metadata study, data from Peer-reviewed publications available in the Perovskite Database (www.perovskitedatabase.com) is used to evaluate the current state of E _g tuning in wide E _g MHP semiconductors. Recent literature on wide E _g MHP semiconductors is examined and the data is extracted and uploaded onto the Perovskite Database. Beyond describing recent highlights and scientific breakthroughs, general trends are drawn from 45,000 individual experimental datasets of MHP solar cell devices. The historical evolution of MHP solar cells is recapitulated, and general conclusions are drawn about the current limits of device performance. Three dominant causes are identified and discussed for the degradation of performance relative to the Shockley-Queisser (SQ) model's theoretical limit for single-junction solar cells: 1) energetically mismatched selective transport materials for wide Eg MHPs, 2) lower optoelectronic quality of wide E _g MHP absorbers, and 3) dynamically evolving compositional heterogeneity due to light-induced phase segregation phenomena.

A hybrid intermediate layer using polymethyl methacrylate (PMMA) functionalized with ionic liquid (IL) is introduced into perovskite/C₆₀ interface where PMMA reduces nonradiative recombination loss, and the introduction of IL additionally alleviates charge accumulation at the PMMA/perovskite interface by enhancing carrier extraction. Overall, as a result of the modification, the efficiency and stability of perovskite/silicon tandem solar cells are improved simultaneously.

Abstract

Monolithic perovskite/silicon tandem solar cells have been attracted much attention in recent years. Despite their high performances, the stability issue of perovskite-based devices is recognized as one of the key challenges to realize industrial application. When comes to the perovskite top subcell, the interface between perovskite and electron transporting layers (usually C₆₀) significantly affects the device efficiency as well as the stability due to their poor adhesion. Here, different from the conventional interfacial passivation using metal fluorides, a hybrid intermediate layer is proposed—PMMA functionalized with ionic liquid (IL)—is introduced at the perovskite/C₆₀ interface. The application of PMMA essentially improves the interfacial stability due to its strong hydrophobicity, while adding IL relieves the charge accumulation between PMMA and the perovskite. Thus, an optimal wide-bandgap perovskite solar cells achieves power conversion efficiency of 20.62%. These cells are further integrated as top subcells with silicon bottom cells in a monolithic tandem structure, presenting an optimized PCE up to 27.51%. More importantly, such monolithic perovskite/silicon cells exhibit superior stability by maintaining 90% of initial efficiency after 1200 h under continuous illumination.

Publication date: March 2024

Source: Nano Energy, Volume 121

Author(s): Ming Luo, Sanlong Wang, Zhao Zhu, Biao Shi, Pengyang Wang, Guofu Hou, Qian Huang, Ying Zhao, Xiaodan Zhang

Publication date: March 2024

Source: Nano Energy, Volume 121

Author(s): Mengmeng Yuan, Hongru Ma, Qingshun Dong, Xiuyun Wang, Linghui Zhang, Yanfeng Yin, Zhehan Ying, Jingya Guo, Wenzhe Shang, Jie Zhang, Yantao Shi

Ionic coupling potassium sorbate with perovskite controls the formation of N-methyl formamidinium ions, which passivate defects and freeze halide segregation in perovskite films under intense light. Target single-junction wide-bandgap perovskite solar cells achieved a record efficiency of 22.00% with photostability of less than 2% decay over 2000 h of operation. Perovskite/TOPCon silicon tandem solar cells achieved an efficiency of 30.72%.

Abstract

Photo-induced halide segregation in wide-bandgap (WBG) perovskite leads to poor stability and limits its application in high-efficiency tandem solar cells. Here, a simple solution strategy to achieve photostable WBG perovskite solar cells (PSCs) with bandgap of ≈1.67 eV by ionic coupling potassium sorbate with defects at the buried perovskite interface is reported. Moreover, the ionic coupled potassium sorbate (ICPS) enables to control the formation of N-methyl formamidinium ions that can selectively passivate the perovskite defects at grain boundaries. As a result, the photo-induced halide segregation in the target perovskite films is frozen under intense light. The target single-junction WBG PSC achieves a record efficiency of 22.00% with an open-circuit voltage (V _OC) of 1.272 V and photostability of less than 2% decay over 2000 h of operation. Perovskite/Silicon tandem solar cells are also fabricated that achieve an efficiency of 30.72% (certified 30.09% @1.087 cm²), which is the highest efficiency reported to date with a tunneling oxide passivating contact (TOPCon) c-Si substrate. The encapsulated tandem device can maintain 97% of its initial efficiency after 1000 h of operation.

A multifunctional polymer additive PMA-AA is developed that enhances quasi-Fermi level splitting (QFLS) through bulk defect passivation and interface energy level alignment, thereby effectively increasing the open-circuit voltage (V _OC) of the perovskite solar cells (PSCs). More importantly, the efficiency of 25.04% and 21.95% is achieved with this strategy for devices and modules, respectively.

Abstract

Perovskite solar cells (PSCs) have attracted extensive attention due to their higher power conversion efficiency (PCE) and simple fabrication process. However, the open-circuit voltage (V _OC) loss remains a significant impediment to enhance device performance. Here, a facile strategy to boost the V _OC to 95.5% of the Shockley-Queisser (S-Q) limit through the introduction of a universal multifunctional polymer additive is demonstrated. This additive effectively passivates the cation and anion defects simultaneously, thereby leading to the transformation from the strong n-type to weak n-type of perovskite films. Benefitting from the energy level alignment and the suppression of bulk non-radiative recombination, the quasi-Fermi level splitting (QFLS) is enhanced.  Consequently, the champion devices with 1.59 eV-based perovskite reach the highest V _OC value of 1.24 V and a PCE of 23.86%. Furthermore, this strategy boosts the V _OC by at least 0.07 V across five different perovskite systems, a PCE of 25.04% is achieved for 1.57 eV-based PSCs, and the corresponding module (14 cm²) also obtained a high PCE of 21.95%. This work provides an effective and universal strategy to promote the V _OC approach to the detailed balance theoretical limit.

The performance of perovskite solar cells (PSCs) is enhanced through the utilization of sputtered NiO _x as a hole-transport layer. The inverted PSCs exhibit a remarkable power conversion efficiency of 20.54%, marking the highest reported performance among sputtered NiO _x -based PSCs. In the results, the adaptability of NiO _x is underscored to diverse perovskite compositions and structural variations, while maintaining stability.

Perovskite solar cells (PSCs) are now approaching their theoretical limits and the optimization of the auxiliary layers is crucial for fully exploiting the potential of perovskite materials. In this study, NiO _x as a hole-transport layer (HTL) for inverted p–i–n PSCs is focused on. Sputtered NiO _x is an attractive p-type HTL owing to its facile processing, wide energy bandgap that prevents electron transfer, high transparency, stability, and effective hole extraction. Despite substantial research on sputtered NiO _x , the relationship between the carrier concentration and work function is still unclear. In this study, the use of sputtered NiO _x as a widely compatible HTL and the effect of its thickness on PSC device performance are investigated. Inverted PSCs with the optimal 10 nm thick NiO _x achieve a remarkable power conversion efficiency of 20.54%, which is the highest reported to date for sputtered NiO _x -based PSCs. Furthermore, PSCs with various NiO _x thicknesses demonstrate similar performances, demonstrating the excellent versatility of NiO _x for use with different perovskite absorbers. The devices exhibit excellent thermal and photostability, retaining 97% of their initial power conversion efficiency at 65 °C and 1 sun illumination for 350 h. Sputtered NiO _x HTLs have great potential for use with diverse perovskite compositions and PSC structures.

In this work, ortho-, meta-, and para-isomers of phenylenediamine (PDA) spacer are introduced. Compared with p-PDA and m-PDA, o-PDA not only reduces the exciton binding energy and facilitates the effective separation of excitons, but also weakens the quantum confinement effect and realizes effective carrier transport. Importantly, 2D DJ (o-PDA)FA₃Sn₄I₁₃ solar cell shows a record power conversion efficiency of 7.18% and enhanced stability.

Abstract

2D Dion–Jacobson (DJ) tin halide perovskite shows impressive stability by introducing diamine organic spacer. However, due to the dielectric confinement and uncontrollable crystallization process, 2D DJ perovskite usually exhibits large exciton binding energy and poor film quality, resulting in unfavorable charge dissociation, carrier transport and device performance. Here, the ortho-, meta-, and para-isomers of phenylenediamine (PDA) are designed for 2D DJ tin halide perovskites. Theoretical simulation and experimental characterizations demonstrate that compared with p-PDA and m-PDA, o-PDA shows larger dipole moment, which further reduces the exciton binding energy for the 2D perovskites. Besides, there is a strong hydrogen bond interaction between o-PDA cation and inorganic octahedron, which not only improves the structural stability, but also induces larger aggregates in the precursor to form dense and uniform high-quality films, and strengthens the antioxidant barrier. More interestingly, femtosecond transient absorption further proves that o-PDA organic spacers can reduce unfavorable small n-phases, resulting in sufficient and effective charge transfer between different n-value. As a result, the 2D DJ (o-PDA)FA₃Sn₄I₁₃ solar cells achieve a record power conversion efficiency of 7.18%. The study furnishes an effective method to optimize the carrier transport and device performance by tailoring the chemical structure of organic spacers.

Single crystal is incorporated into the perovskite precursor solution and 4,6-dimethyl-2-mercaptopyrimidine is introduced to achieve a champion power conversion efficiency of 20.24% on an effective area of 1.012 cm² and a power-to-weight ratio of more than 3000 W kg⁻¹ on ultra-thin stainless-steel substrate.

Ultra-thin stainless-steel substrates with excellent water-oxygen barrier properties and high thermal and electrical conductivities are suitable for the fabrication of lightweight and flexible perovskite solar cells (FPSCs). However, the deposition of dense perovskite films on stainless steel by the solution method is crucial because short circuits caused by perovskite holes are fatal to parallel structures. Herein, a single crystal (SC) is incorporated into the precursor solution to reduce the formation of holes in perovskite films on smooth stainless-steel substrates. Additionally, a magnetic method is developed based on the properties of stainless steel to fix and fabricate FPSCs nondestructively on ultra-thin stainless-steel films with a thickness as low as 5 μm. Furthermore, 4,6-dimethyl-2-mercaptopyrimidine (DMI) was introduced to passivate the surface of the perovskite film, optimizing the contact properties of the perovskite heterojunction and adjusting the energy level of the perovskite/C₆₀ interface. Finally, ultra-thin FPSCs achieved a champion power conversion efficiency (PCE) of 20.24% on an active area of 1.012 cm² and a power-to-weight ratio over 3000 W kg⁻¹. Moreover, under continuous illumination, the stainless-steel substrates exhibited better photothermal stability than the polymer substrates. This method provides a basis for the fabrication of lightweight, low-cost, and large-area FPSCs.

W e present a new 1.80 eV wide-bandgap (WBG) perovskite treated with piperazinium iodide (PI) for all-perovskite tandem solar cells. This treatment eliminates non-radiative recombination losses and reduces defect density resulting in an open circuit voltage of 1.36 V and enhanced photostability. Combined with a narrow bandgap (NBG) perovskite, this enables a tandem cell with a certified scan efficiency of 27.5%.

Abstract

All-perovskite tandem solar cells show great potential to enable the highest performance at reasonable costs for a viable market entry in the near future. In particular, wide-bandgap (WBG) perovskites with higher open-circuit voltage (V _OC) are essential to further improve the tandem solar cells’ performance. Here, a new 1.8 eV bandgap triple-halide perovskite composition in conjunction with a piperazinium iodide (PI) surface treatment is developed. With structural analysis, it is found that the PI modifies the surface through a reduction of excess lead iodide in the perovskite and additionally penetrates the bulk. Constant light-induced magneto-transport measurements are applied to separately resolve charge carrier properties of electrons and holes. These measurements reveal a reduced deep trap state density, and improved steady-state carrier lifetime (factor 2.6) and diffusion lengths (factor 1.6). As a result, WBG PSCs achieve 1.36 V V _OC, reaching 90% of the radiative limit. Combined with a 1.26 eV narrow bandgap (NBG) perovskite with a rubidium iodide additive, this enables a tandem cell with a certified scan efficiency of 27.5%.

Sufficient conversion of residual photoinstable PbI₂ into robust 1D perovskite (EMIMPbI₃) can improve device stability, while the formation of an interfacial dipole layer at the SnO₂/perovskite interface can reduce the energetic mismatch via a single process. The optimized device delivers an efficiency of 24.28 % and a remarkable open circuit voltage of 1.19 V, accompanied with excellent humidity and operational stability.

Abstract

Eliminating the undesired photoinstability of excess lead iodide (PbI₂) in the perovskite film and reducing the energy mismatch between the perovskite layer and heterogeneous interfaces are urgent issues to be addressed in the preparation of perovskite solar cells (PVSCs) by two-step sequential deposition method. Here, the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF₄) is employed to convert superfluous PbI₂ to more robust 1D EMIMPbI₃ which can withstand lattice strain, while forming an interfacial dipole layer at the SnO₂/perovskite interface to reconfigure the interfacial energy band structure and accelerate the charge extraction. Consequently, the unencapsulated PVSCs device attains a champion efficiency of 24.28 % with one of the highest open-circuit voltage (1.19 V). Moreover, the unencapsulated devices showcase significantly improved thermal stability, enhanced environmental stability and remarkable operational stability accompanied by 85 % of primitive efficiency retained over 1500 h at maximum power point tracking under continuous illumination.

Using cesium cyclopropane acids (C₃) gives high crystallization quality in an all-inorganic perovskite CsPbI₂Br prepared in a wide ambient moisture window (RH: 25–65 %). The resultant CsPbI₂Br solar cells exhibit a high efficiency (>17 %) and excellent environmental stability. The vaporization enthalpy of the side product DMA-acid (adjustable by C₃ loads) modifies the perovskite crystallization and device performance under different humidity.

Abstract

While all-inorganic halide perovskites (iHPs) are promising photovoltaic materials, the associated water sensitivity of iHPs calls for stringent humidity control to reach satisfactory photovoltaic efficiencies. Herein, we report a moisture-insensitive perovskite formation route under ambient air for CsPbI₂Br-based iHPs via cesium cyclopropane acids (C₃) as a compound introducer. With this approach, appreciably enhanced crystallization quality and moisture tolerance of CsPbI₂Br are attained. The improvements are attributed to the modified evaporation enthalpy of the volatile side product of DMA-acid initiated by Cs-acids. As such, the water-involving reaction is directed toward the DMA-acids, leaving the target CsPbI₂Br perovskites insensitive to ambient humidity. We highlight that by controlling the C₃ concentration, the dependence of power conversion efficiency (PCE) in CsPbI₂Br devices on the humidity level during perovskite film formation becomes favorably weakened, with the PCEs remaining relatively high (>15 %) associated with improved device stability for RH levels changed from 25 % to 65 %. The champion solar cells yield an impressive PCE exceeding 17 %, showing small degradations (<10 %) for 2000 hours of shell storage and 300 hours of 85/85 (temperature/humidity) tests. The demonstrated C₃-based strategy provides an enabler for improving the long-sought moisture-stability of iHPs toward high photovoltaic device performance.

A SnO_x interfacial layer with gradient compositions has been designed to overcome the dilemma between interface defects and electrical properties. Owing to the formation of homojunction, the gradient SnO_x structure facilitates the charge extraction, enabling the perovskite–silicon tandem solar cells based on industrially fully-textured silicon to achieve a certified efficiency of over 28%.

Abstract

Atomic layer deposition (ALD) growth of conformal thin SnO _x films on perovskite absorbers offers a promising method to improve carrier-selective contacts, enable sputter processing, and prevent humidity ingress toward high-performance tandem perovskite solar cells. However, the interaction between perovskite materials and reactive ALD precursor limits the process parameters of ALD-SnO _x film and requires an additional fullerene layer. Here, it demonstrates that reducing the water dose to deposit SnO _x can reduce the degradation effect upon the perovskite underlayer while increasing the water dose to promote the oxidization can improve the electrical properties. Accordingly, a SnO _x buffer layer with a gradient composition structure is designed, in which the compositionally varying are achieved by gradually increasing the oxygen source during the vapor deposition from the bottom to the top layer. In addition, the gradient SnO _x structure with favorable energy funnels significantly enhances carrier extraction, further minimizing its dependence on the fullerene layer. Its broad applicability for different perovskite compositions and various textured morphology is demonstrated. Notably, the design boosts the efficiencies of perovskite/silicon tandem cells (1.0 cm²) on industrially textured Czochralski (CZ) silicon to a certified efficiency of 28.0%.

Current and voltage matching via the adjustment of the cell width of perovskite and organic solar modules is experimentally demonstrated, enabling a higher-than-individual efficiency of 14.94% over an aperture area of 20.25 cm². Remarkably, the 2T mechanically-stacked tandem was built with modules having the non-complementary semiconductors FAPbBr₃ and PM6:Y6:PC₆₁BM, thus overcoming the bandgap restrictions imposed by a monolithic structure.

Photocurrent matching in conventional monolithic tandem solar cells is achieved by choosing semiconductors with complementary absorption spectra and by carefully adjusting the optical properties of the complete top and bottom stacks. However, for thin film photovoltaic technologies at the module level, another design variable significantly alleviates the task of photocurrent matching, namely the cell width, whose modification can be readily realized by the adjustment of the module layout. Herein, this concept is demonstrated at the experimental level for the first time for a 2T-mechanically stacked perovskite (FAPbBr₃)/organic (PM6:Y6:PCBM) tandem mini-module, an unprecedented approach for these emergent photovoltaic technologies fabricated in an independent manner. An excellent I _sc matching is achieved by tuning the cell widths of the perovskite and organic modules to 7.22 mm (PCE _PVKT-mod = 6.69%) and 3.19 mm (PCE _OPV-mod = 12.46%), respectively, leading to a champion efficiency of 14.94% for the tandem module interconnected in series with an aperture area of 20.25 cm². Rather than demonstrating high efficiencies at the level of small lab cells, this successful experimental proof-of-concept at the module level proves to be particularly useful to couple devices with non-complementary semiconductors, either in series or in parallel electrical connection, hence overcoming the limitations imposed by the monolithic structure.

Succinic acid derivative with multiple active sites and optimal spatial positions maximizes the defect binding energy, improves the film quality, and depresses the non-radiative recombination of the perovskite, giving a record efficiency of 25.41% for RbCsFAMA-based quadruple-cation perovskite devices.

Abstract

Minimizing interfacial charged traps in perovskite films is crucial for reducing the non-radiative recombination and improving device performance. In this study, succinic acid (SA) derivatives varying active sites and spatial configurations are designed to modulate defects and crystallization in perovskite film. The SA derivative with two symmetric Br atoms, dibromosuccinic acid (DBSA), exhibits the optimal spatial arrangement for defect passivation. Experimental and theoretical results indicate that the carboxyl group and atomic Br in DBSA synergistically interact with the under-coordinated Pb²⁺. Moreover, the strong electronegativity of Br efficiently stabilizes the formamidinium cation via electrostatic interaction. Consequently, film quality is significantly improved and non-radiative recombination is markedly depressed, resulting in a photoluminesence lifetime of exceeding 4 µs of and a carrier diffusion length of 3 µm. An exceptional efficiency of 25.41% (certified at 25.00%) along with a high fill factor of 84.39% and excellent long-term operational stability have been achieved finally.

The development of a damp-heat-stable multiple-cation perovskite solar cell by applying various surface treatment strategies and an effective encapsulation structure is presented. The best-performing device achieves 20.82% efficiency and shows superior stability for 500 h under conditions at 85 °C and 85% relative humidity. This shows great promise as a potential solution for the modularization of perovskite solar cells.

Multiple-cation perovskites have been extensively researched for stability enhancement, but limited literature exists on CsFAMA (CFM) solar cell stability under harsh temperature and humidity. This article focuses on the development of damp-heat-resistant CFM-based perovskite solar cells (PSCs) through the implementation of various surface treatment strategies, including antisolvent treatment (AST) control and alkyl-type interfacial passivation, while also proposing an effective encapsulation structure. The Cs⁺ ratio in Cs _x (FA_0.91MA_0.09)_1−x Pb(I,Br)₃ perovskites is varied in the range of x = 0 to 0.362, and the AST times are explored by adjusting from 8 to 15 s. Remarkably, a power conversion efficiency (PCE) is achieved with significant improvements in open-circuit voltage and fill factor at an AST time of 12 s. Through precise tuning of the Cs ratio to x = 0.17 (Cs_0.17(FA_0.91MA_0.09)_0.83Pb(I,Br)₃) and introduction of an octyl-ammonium iodide interlayer, the highest-performing device with a PCE of 20.82% is obtained. Additionally, a low-temperature vacuum lamination is employed, and the conducive tape in a twisted form is extended, which effectively seals the device. This results in superior stability for 500 h under damp-heat conditions at 85 °C and 85% relative humidity. This encapsulation method holds significant promise as a potential solution for the modularization of PSCs.

The bipolar photoresponse based on spontaneously formed wide-narrow bandgap-laminated perovskite films by BiI₃ doping is demonstrated. Under the visible/near-infrared (NIR) light, corresponding electrons are easier to be separated and transported by the SnO₂/PC₆₁BM to the bottom/top electrodes. Benefiting from the wavelength-dependent bipolar response, the signal secure optical communication (SOC) system is realized based on hidden properties of the bipolar signals.

Abstract

Perovskite photodetectors with bipolar photoresponse characteristics are expected to be applied in the field of secure optical communication (SOC). However, how to realize the perovskite photodetector with bipolar response remains challenging. Herein, by introducing bismuth iodide (BiI₃) into Sn-Pb mixed perovskite precursor solution, 2D perovskite FA₃Bi₂I₉ is spontaneously formed at the bottom to realize a wide-narrow bandgap-laminated perovskite film. Wavelength-dependent bipolar response is realized based on the absorption difference of the photoactive region with different bandgap combined with the carrier competition of the homotypic transport layer adopted in the as-fabricated photodetector. Under the visible/near-infrared (NIR) light irradiation, the bottom/top of the film generates a higher carrier concentration, where electrons are easier to be separated and transported by the SnO₂/PC₆₁BM to the bottom/top electrodes, respectively, resulting in a negative and positive bipolar response. Finally, based on positive NIR signal as the effective signal and negative visible signal as the interference signal, the SOC system is realized, where the positive NIR signal is well hidden by the negative visible signal. This work provides a simple and feasible strategy for fabrication of laminated perovskite films to achieve bipolar response.

Herein, an electron transport layer ink is designed using hybrid fullerenes composed of mixed C₆₀, phenyl C₆₁ butyric acid methyl ester, and indene-C₆₀ bisadduct. This electron transport layer exhibits high conductivity, good energy-level alignment, and low interfacial nonradiative recombination. The all-perovskite tandem solar modules achieve a champion power conversion efficiency of 23.3% (aperture area = 20.25 cm²).

Abstract

All-perovskite tandem solar cells offer the potential to surpass the Shockley–Queisser (SQ) limit efficiency of single-junction solar cells while maintaining the advantages of low-cost and high-productivity solution processing. However, scalable solution processing of electron transport layer (ETL) in p-i-n structured perovskite solar subcells remains challenging due to the rough perovskite film surface and energy level mismatch between ETL and perovskites. Here, scalable solution processing of hybrid fullerenes (HF) with blade-coating on both wide-bandgap (≈1.80 eV) and narrow-bandgap (≈1.25 eV) perovskite films in all-perovskite tandem solar modules is developed. The HF, comprising a mixture of fullerene (C₆₀), phenyl C₆₁ butyric acid methyl ester, and indene-C₆₀ bisadduct, exhibits improved conductivity, superior energy level alignment with both wide- and narrow-bandgap perovskites, and reduced interfacial nonradiative recombination when compared to the conventional thermal-evaporated C₆₀. With scalable solution-processed HF as the ETLs, the all-perovskite tandem solar modules achieve a champion power conversion efficiency of 23.3% (aperture area = 20.25 cm²). This study paves the way to all-solution processing of low-cost and high-efficiency all-perovskite tandem solar modules in the future.

Recent post-treatment technological reforms toward perovskite thin films are summarized, and the principal functions of the post-treatment strategies on the design of high-quality perovskite films are thoroughly analyzed. Then, the latest research progress of thermal annealing (TA)-related and TA-free techniques is summarized and discussed. Finally, an outlook of the prospect trends of these post-treatment techniques is given.

Abstract

Incredible progress in photovoltaic devices based on hybrid perovskite materials has been made in the past few decades, and a record-certified power conversion efficiency (PCE) of over 26% has been achieved in single-junction perovskite solar cells (PSCs). In the fabrication of high-efficiency PSCs, the postprocessing procedures toward perovskites are essential for designing high-quality perovskite thin films; developing efficient and reliable post-treatment techniques is very important to promote the progress of PSCs. Here, recent post-treatment technological reforms toward perovskite thin films are summarized, and the principal functions of the post-treatment strategies on the design of high-quality perovskite films have been thoroughly analyzed by dividing into two categories in this review: thermal annealing (TA)-related technique and TA-free technique. The latest research progress of the above two types of post-treatment techniques is summarized and discussed, focusing on the optimization of postprocessing conditions, the regulation of perovskite qualities, and the enhancement of device performance. Finally, an outlook of the prospect trends and future challenges for the fabrication of the perovskite layer and the production of highly efficient PSCs is given.

A fully aromatic carbazole-based self-assembled monolayer, denoted as MeO-PhPACz, is employed as a hole-selective layer (HSL) in inverted wide-band gap perovskite solar cells (PSCs). The fully aromatic configuration is crucial in promoting the formation of a dense and highly ordered HSL, improving hole extraction/transport efficiency. The optimized wide-band gap PSCs attain a power conversion efficiency (PCE) of 21.10 % and excellent UV resistance.

Abstract

Ultraviolet-induced degradation has emerged as a critical stability concern impeding the widespread adoption of perovskite solar cells (PSCs), particularly in the context of phase-unstable wide-band gap perovskite films. This study introduces a novel approach by employing a fully aromatic carbazole-based self-assembled monolayer, denoted as (4-(3,6-dimethoxy-9H-carbazol-9-yl)phenyl)phosphonic acid (MeO-PhPACz), as a hole-selective layer (HSL) in inverted wide-band gap PSCs. Incorporating a conjugated linker plays a pivotal role in promoting the formation of a dense and highly ordered HSL on substrates, facilitating subsequent perovskite interfacial interactions, and fostering the growth of uniform perovskite films. The high-quality film could effectively suppress interfacial non-radiative recombination, improving hole extraction/transport efficiency. Through these advancements, the optimized wide-band gap PSCs, featuring a band gap of 1.68 eV, attain an impressive power conversion efficiency (PCE) of 21.10 %. Remarkably, MeO-PhPACz demonstrates inherent UV resistance and heightened UV absorption capabilities, substantially improving UV resistance for the targeted PSCs. This characteristic holds significance for the feasibility of large-scale outdoor applications.

Herein, an effective redox strategy is developed to improve the quality of perovskite film by incorporating 4-fluorobenzothiohydrazide (FBTH) into cesium lead triiodide (CsPbI₃) precursor solution. A new compound FBTH-I is obtained, which can passivate the Pb-related defects and restrain I⁻ migration. Consequently, FBTH-treated CsPbI₃ perovskite solar cell (PSC) achieves a distinguished PCE of 21.41% with an excellent V _oc of 1.231 V and an outstanding operational stability.

Abstract

To simultaneously stabilize cesium lead triiodide (CsPbI₃) precursor solution and passivate the defects in CsPbI₃ film is greatly significant for achieving highly stable and efficient CsPbI₃ perovskite solar cells (PSCs). Herein, an effective redox 4-fluorobenzothiohydrazide (FBTH) is developed to stabilize the precursor solution and passivate iodine/lead-related defects for high-quality CsPbI₃ film. The comprehensive research confirms that 1) a new compound FBTH-I is obtained from an effective redox interaction between FBTH and molecular iodine (I₂) in perovskite precursor solution, which can effectively impede the formation of I₂ molecule and restrain I⁻ migration in perovskite film by forming N–H···I bond; 2) FBTH-I can also passivate Pb-related defects via forming S···Pb interaction. Consequently, the CsPbI₃ PSC based on FBTH-treated precursor solution exhibits a fascinating power conversion efficiency (PCE) of 21.41%, which is one of the highest PCE values among the reported pure CsPbI₃ PSCs so far, and an outstanding stability against the harsh conditions, such as thermal annealing and continuous light-illumination.

Nature Energy, Published online: 20 November 2023; doi:10.1038/s41560-023-01383-9