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Perovskite solar cells have shown great potential in the field of underwater solar cells due to their excellent optoelectronic properties; however, their underwater performance and stability still hinder their practical use. In this research, a 1H,1H,2H,2H-heptadecafluorodecyl acrylate (HFDA) anti-reflection coating (ARC) was introduced as a high-transparent material for encapsulating perovskite solar modules (PSMs). Optical characterization results revealed that HFDA can effectively reduce reflection of light below 800 nm, aiding in the absorption of light within this wavelength range by underwater solar cells. Thus, a remarkable efficiency of 14.65% was achieved even at a water depth of 50 cm. And, the concentration of Pb2+ for HFDA-encapsulated film is significantly reduced from 186 to 16.5 ppb after being immersed in water for 347 h. Interestingly, the encapsulated PSMs still remained above 80% of their initial efficiency after continuous underwater illumination for 400 h. Furthermore, being exposed to air, the encapsulated PSMs maintained 94% of their original efficiency after 1000 h light illumination. This highly transparent ARC shows great potentials in enhancing the stability of perovskite devices, applicable not only to underwater cells but also extendable to land-based photovoltaic devices. [ABSTRACT FROM AUTHOR]

In recent years, the organic–inorganic hybrid perovskite community has been widely employed as the photo-active layer in optical-electronic devices. The black α-phase formamidinium lead iodide (FAPbI3) is the most popular perovskite for realizing high-efficiency solar cells due to its suitable bandgap. However, the issue of stability is also a concern in the research on FAPbI3 solar cells. In this study, different ammonium ions, such as butylamine (BA), guanidine (GA), and butylene diamine (BDA), which are commonly used to construct two-dimensional perovskites, including Ruddlesden–Popper, Dion–Jacobson, and alternating cations in the interlayer space, respectively, were introduced in the fabrication of FAPbI3 using a sequential deposition method. Several structures of PbI2 precursor films were formed by introducing the aforementioned ions, which exhibited different arrangements and connection modes in lead iodides. BA-PbI2 precursor films exhibited higher specific surface areas, which were beneficial to the diffusion, ion exchange, and sequential reaction of FA+. The BDA-PbI2 precursor film slowed down the sequential reaction of FAPbI3 because of reduced van der Waals bonds. The nucleation dynamics and degradation processes of perovskites were deeply investigated in this study. Solar cells based on BA-PbI2, GA-PbI2, and BDA-PbI2 were also fabricated. [ABSTRACT FROM AUTHOR]

Inorganic tin–lead perovskites with low bandgap (1.2–1.4 eV) are desired absorber materials for solar cells owing to their ideal bandgap and compositional stability. However, such tin–lead perovskites are currently subject to inferior power conversion efficiency (PCE) and the origin remains unclear. Here, for the first time, we report the metal-cation-derived unsynchronized crystallization behavior of inorganic tin–lead perovskite, exemplifying by a representative composition CsPb0.7Sn0.3I3. A tin-perovskite-targeted crystallization modulation agent, 1-(4-fluorophenyl) piperazine (1-4FP), is introduced to synchronize the B-site alloying through its strong targeted bonding with SnI2, resulting in substantially enhanced film quality with better morphology and photoelectrical properties. Furthermore, first-principles molecular dynamics simulations reveal that the agent regulates the crystallization route toward the pure phase of CsPb0.7Sn0.3I3 by suppressing the preforming of tin perovskite. With our proposed approach, the best device attains PCE of 17.55%, which is record-high for inorganic tin–lead perovskite solar cells. In addition, treated devices show excellent stability with only 10% and negligible loss after being exposed to 1 sun intensity for 700 h and being stored in N2 after over 4000 h, respectively. Our findings open a new avenue of crystallization route design in inorganic tin–lead perovskites, so as to obtaining high-quality perovskite films and associated solar cells. [ABSTRACT FROM AUTHOR]

Steering the crystallization of two-dimensional (2D) perovskite film is an important strategy to improve the power conversion efficiency (PCE) of 2D perovskite solar cells (PVSCs). In this paper, the deionized water (H2O) additive is introduced into the perovskite precursor solution to prepare high-quality 2D perovskite films. The 2D perovskite film treated with 3% H2O shows a good surface morphology, increased crystal size, enhanced crystallinity, preferred orientation, and low defect density. The fabricated 2D PVSC with 3% H2O exhibits a higher PCE compared with that without H2O (12.15% vs 2.29%). Furthermore, the shelf stability of unsealed devices with 3% H2O under ambient environment is significantly improved. This work provides a simple method to prepare high-quality 2D perovskite films for efficient and stable 2D PVSCs. [ABSTRACT FROM AUTHOR]

Generally, defects passivation and stability enhancement against humidity are two independent open questions in exploring high-performance perovskite solar cells. Here, a high-efficient and stable perovskite solar cell is fabricated by introducing dual-functional 2-Fluorothiophenol (FTP) as an anti-solvent additive. The FTP can not only greatly reduce the defects within perovskites, but also effectively improve the hydrophobicity of the perovskite films. [Display omitted] • Dual-functional FTP blended with CB is used as an antisolvent for the first time. • FTP incorporation induces the oriented crystallization and reduces the defects. • FTP boosts the efficiency from 16.86% to 20.01% for 1.0 cm2 devices. • The PSCs with FTP incorporation exhibit an outstanding humidity stability. Ionic defects and humidity instability are the main limitations to realize the commercialization of FA-based perovskite solar cells. To overcome these issues, here, we report a dual-functional molecular 2-Fluorothiophenol (FTP) to achieve high-quality FA-based perovskites with simultaneously efficient defects passivation and improved hydrophobicity. It is revealed that SH¯ groups of FTP induce highly oriented crystallization toward (0 0 1) crystal plane of cubic-phase Cs 0.05 FA 0.95 PbI 3 perovskite structure, thus improving the charge carrier transport. Moreover, a strong Lewis acid-base interaction between the SH¯ group and Pb2+ in perovskite is of great benefit to passivate the surface and grain boundary defects, with additional merit for improving humidity stability of the FA-based perovskite films in conjunction with the hydrophobic group of FTP. The introduction of FTP boosts the efficiency from 20.30% to 22.66% for 0.04 cm2 solar cells and from 16.86% to 20.01% for 1.0 cm2 devices. More importantly, the solar cells demonstrate excellent humidity stability, which can retain 90% of their original efficiency after being kept for 80 days under ambient air conditions. [ABSTRACT FROM AUTHOR]

The HC(NH2)2+(FA+) is a well‐known substitute to CH3NH3+(MA+) for its capability to extend light utilization for improved power conversion efficiency for perovskite solar cells; unfortunately, the dark cubic phase (α‐phase) can easily transition to the yellow orthorhombic phase (δ‐phase) at room temperature, an issue that prevents its commercial application. In this report, an inorganic material (NbF5) is developed to stabilize the desired α‐phase perovskite material by incorporating NbF5 additive into the perovskite films. It is found that the NbF5 additive effectively suppresses the formation of the yellow δ‐phase in the perovskite synthesis and aging process, thus enhancing the humidity and light‐soaking stability of the perovskite film. As a result, the perovskite solar cells with the NbF5 additive exhibit improved air stability by tenfold, retaining nearly 80% of their initial efficiency after aging in air for 50 d. In addition, under full‐sun AM 1.5 G illumination of a xenon lamp without any UV‐reduction, the perovskite solar cells with the NbF5 additive also show fivefold improved illumination stability than the control devices without NbF5. [ABSTRACT FROM AUTHOR]

The Cs‐based inorganic perovskite solar cells (PSCs), such as CsPbI2Br, have made a striking breakthrough with power conversion efficiency (PCE) over 16% and potential to be used as top cells for tandem devices. Herein, I− is partially replaced with the acetate anion (Ac−) in the CsPbI2Br framework, producing multiple benefits. The Ac− doping can change the morphology, electronic properties, and band structure of the host CsPbI2Br film. The obtained CsPbI2−xBr(Ac)x perovskite films present lower trap densities, longer carrier lifetimes, and fast charge transportation compared to the host CsPbI2Br films. Interestingly, the CsPbI2−xBr(Ac)x PSCs exhibit a maximum PCE of 15.56% and an ultrahigh open circuit voltage (Voc) of 1.30 V without sacrificing photocurrent. Notably, such a remarkable Voc is among the highest values of the previously reported CsPbI2Br PSCs, while the PCE far exceeds all of them. In addition, the obtained CsPbI2−xBr(Ac)x PSCs exhibit high reproducibility and good stability. The stable CsPbI2−xBr(Ac)x PSCs with high Voc and PCE are desirable for tandem solar cell applications. [ABSTRACT FROM AUTHOR]

A simple coalloying strategy is applied to improve the efficiency and stability of FA0.85MA0.15PbI3 perovskite solar cells (PSCs) by using cesium acetate (CsAc) as an additive. It is found that the simultaneous incorporation of cation (Cs+) and anion (Ac−) into the FA0.85MA0.15PbI3 film is an effective approach to realize lattice contraction, grain size enlargement, photoelectric properties improvement, band structure modulation, and therefore the optimization of the efficiency and stability of PSCs. At optimal CsAc alloying, the FA0.85MA0.15PbI3 PSCs achieve a maximum power conversion efficiency (PCE) of 21.95% and an average of over 21%. In addition, the alloyed PSCs retain 97% of their initial PCE values after aging for 55 days in air without encapsulation. [ABSTRACT FROM AUTHOR]

Inorganic cesium lead halide perovskite solar cells (PSCs), such as CsPbI2Br, have made a striking breakthrough with a power conversion efficiency of over 16%. However, CsPbI2Br is known to be very sensitive to moisture, and the intrinsic long‐term stability of CsPbI2Br film remains a critical challenge. Interface engineering has been proven to be an effective way for solving the instability‐to‐moisture issue and enhancing the performance of inorganic–organic hybrid PSCs, while there are a few reports on interface engineering for inorganic PSCs. Here, a conjugated polymer, poly(N‐alkyldiketopyrrolo‐pyrrole dithienylthieno[3,2‐b]thio‐phene) (DPP‐DTT), with high mobility is introduced as a novel interface passivation for CsPbI2Br PSCs, which can significantly reduce nonradiative recombination in perovskite, leading to significant enhancement in both efficiency and stability of CsPbI2Br PSCs. Through DPP‐DTT passivation, a champion efficiency of 15.14% is obtained in CsPbI2Br PSCs. Moreover, the Lewis base DPP‐DTT can serve as an ultrahydrophobic agent to hold the photovoltaic performance of CsPbI2Br PSCs under ambient environment with humidity or thermal stress. These results provide a simple while highly effective route of fabricating the highly efficient and stable inorganic PSCs. [ABSTRACT FROM AUTHOR]

In planar perovskite solar cells (PSCs), defect‐induced recombination at the interface between the perovskite and hole transport layer (HTL) leads to a large potential loss and performance deterioration. Therefore, an effective method for improving interfacial properties is critical to boost the performance and stability of PSCs. Herein, a novel surface engineering technology is reported for passivating the perovskite surface with the polyfluoro organic compound tris(pentafluorophenyl)boron (TPFPB), which can yield large perovskite grains, reduced defect densities, and improved charge transport and phase stability for the perovskite film, and enhanced power conversion efficiency (PCE) and stability for PSCs. Using this strategy, a champion FA0.85MA0.15PbI3 perovskite cell achieves a high PCE of 21.6% as well as significantly improved air and light stabilities. This work demonstrates that TPFPB is a promising material for crystallization control and defect passivation and paves a new path for mitigating defects and further increasing the performance of planar PSCs. [ABSTRACT FROM AUTHOR]

• Combined 1-4FP additive and post-treatment strategy was adopted in tin–lead PSCs. • High-quality perovskite film was obtained via significant surface reconstruction. • Crosslinking neighboring perovskite grains with N-H bonds prevented tin oxidation. • Target PSC delivered a PCE of 17.19 % with a record small Voc deficit of 0.426 V. • 17.19% is the highest efficiency among all-inorganic Pb-Sn PSCs reported to date. Inorganic CsPb 0.7 Sn 0.3 I 3 perovskites with low-bandgap (1.2 to 1.4 eV) are desired absorber materials for solar cells owing to their ideal bandgap and compositional stability. However, the performances of inorganic Pb-Sn perovskite solar cells are much lower than their Pb-based and hybrid Pb-Sn (e.g. CsPbX 3 and FAMAPbSnX 3) PSCs, which might be ascribed to its poor film-forming morphology and easy oxidation of Sn2+ at the surface. Here, for the first time, a combined 1-(4-fluorophenyl) piperazine (1-4FP) additive and 1-4FP post-treatment strategy was adopted to obtain high-quality pinhole-free films through a significant surface reconstruction. Specifically, the interaction introduced by 1-4FP post-treatment can effectively prevent the inevitable Sn2+ oxidation on perovskite surface, resulting from crosslinking neighboring perovskite grains with hydrogen bonds of amine group binding to the perovskite surface. As a result, the device treated by this combined strategy achieved a PCE of 17.19 %, which is the highest efficiency of Pb-Sn alloyed inorganic PSCs (sub-1.4 eV) reported to date. In addition, the unsealed 1-4FP-treated devices maintained their initial efficiencies of approximately 100 % after storage in a nitrogen atmosphere for 4000 h. Our findings open a new avenue to obtain high-quality inorganic Pb-Sn perovskite films and associated solar cells. [ABSTRACT FROM AUTHOR]

The defect passivation in the bulk of metal oxide electron transport layers and at the electron transport layers/perovskite interfaces is one of the pivotal roles that enhance electron injection and extraction to gain the high-performing planar perovskite solar cells. Herein, we incorporate the sodium chloride dopants into the compact TiO 2 as electron transport layers at a low temperature of 200 °C. It is demonstrated that the appropriate sodium chloride additive can effectively passivate the bulk and surface defects of the intrinsic TiO 2 , suppressing oxygen vacancies-induced nonradiative recombination centers and improving electron extraction and collection. Simultaneously, the proper sodium chloride treatment remarkably enhances the TiO 2 conductivity, reduces the water contact angle, and further indirectly optimizes the morphology of perovskite layer. With 5.0 mol% sodium chloride-incorporated TiO 2 , the perovskite solar cells exhibit the enhancement in the photovoltaic parameters because of the lower carrier recombination and faster charge transport, contributing to efficiency up to 19.84% with small hysteresis. More importantly, this sodium chloride-modified electron transport layer based perovskite solar cell also emerge a considerable long-term air-storage stability of about 80% of its initial efficiency after 800 h. Image 1 • NaCl additive effectively passivates defects in the bulk and surface of TiO2 film. • Perovskite layer fabricated on 5% NaCl-doped substrate presents large grain growth. • The device with 5% NaCl-doped ETL yields the PCE of 19.84% with small hysteresis. • The PSC with 5% NaCl-doped ETL shows great long-term air-storage stability. [ABSTRACT FROM AUTHOR]

Hole transport layers (HTLs) plays critical role in CsPbI 2 Br perovskite solar cells (PSCs). However, few studies have been done to develop new and sensitive-dopant-free HTL for CsPbI 2 Br PSCs. Here, a low-cost fluorinated N',N',N'',N''-tetrakis(4-methoxyphenyl)spiro[fluorene-9,9'-xanthene]-2,7-diamine (2mF-X59) was synthesized and applied as sensitive-dopant-free HTL into CsPbI 2 Br PSCs. After modified the 2mF-X59 and CsPbI 2 Br surface by 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquino-dimethane (F4-TCNQ), a maximum power conversion efficiency (PCE) of 14.42% was obtained for CsPbI 2 Br PSC with an impressive open-circuit voltage (V oc) of 1.23 V, which is higher than that of the most previously reported CsPbI 2 Br PSCs with the doped Spiro-OMeTAD. More importantly, the CsPbI 2 Br PSCs with the newly developed HTLs showed remarkable stability retaining more than 94% of their initial PCE value after aging in air for 30 days without encapsulation. Therefore, we firmly believe that our new 2mF-X59 HTL created via molecular engineering is a promising candidate for preparing high performance CsPbI 2 Br PSCs. A new sensitive-dopant-free HTL (2mF-X59) was synthesized and successfully applied in a planar CsPbI 2 Br PSC. A power conversion efficiency (PCE) of 14.42% was obtained in the CsPbI 2 Br PSC with 2mF-X59 + F4-TCNQ as HTL by interface engineering. The unencapsulated device displayed remarkable stability, retaining above 94% of its initial PCE after storing in ambient atmosphere for 30 days. Image 1 • 2mF-X59 was firstly synthesized to instead of spiro-OMeTAD in CsPbI 2 Br perovskite solar cells. As we know, few works have been report about using new HTL in inorganic perovskite solar cell. • F4-TCNQ was used as additive for 2mF-X59 hole transport layer (HTL), A High efficiency of 13.42% was obtained in CsPbI 2 Br solar cell with 2mF-X59 + F4TCNQ HTL, which is comparable to device with spiro-OMeTAD + Li-TFSI + t-BP as HTL (PCE = 13.75%). • In order to further improve the efficiency of CsPbI 2 Br solar cell, F4-TCNQ was used to passivate the surface of CsPbI 2 Br film. The efficiency of CsPbI 2 Br solar cell with 2mF-X59 + F4TCNQ HTL was further improved from 13.42 to 14.42%. [ABSTRACT FROM AUTHOR]