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Inorganic-organic hybrid lead halide perovskites are emerging optoelectronic materials for solar cell application. However, the toxicity concerns and poor stability largely hamper their practical applications. For these reasons, the search for "perovskite-inspired" alternatives, having the same advantages but overcoming the drawbacks of the lead-based one, has become an important sector in the field. Among the candidates, Bi3+ and Sb3+ containing materials are of great interest, due to their electronic structures resembling the Pb2+. Bismuth/antimony chalcohalides have been known for a long time as the potential absorber in photovoltaics, even if their performances are still low. Interestingly, pnictogen chalcohalides can be the stepping stone toward numerous quaternary compounds, including some perovskite structures. The understanding of the fundamental properties and the current limitations of both the starting ternary compounds and the final quaternary materials can allow the achievement of improved photovoltaic absorbers, stable, and efficient. In this review, the fundamental properties and device performances of many ternary pnictogen chalcohalides and the derived quaternary compounds are summarized, focusing on the different preparation strategies. [ABSTRACT FROM AUTHOR]

It is widely believed that excess/residual lead iodide (PbI2) can affect the performance of perovskite solar cells. Moderate PbI2 can enhance efficiency by passivating defects, while extremely active PbI2 leads to non‐negligible hysteresis effects and reduces device stability. Although several efforts are made to investigate the role of excess PbI2, its impact is still underestimated. Recent advances further demonstrate the extraordinary potential of modifying excess PbI2; however, a comprehensive study is required to obtain a deeper understanding. Herein, the important breakthroughs regarding excess PbI2 are reviewed and the mechanism of excess PbI2 in terms of efficiency and stability is rethought. In addition, the origins, verification, and regulation of residual PbI2 are summarized. [ABSTRACT FROM AUTHOR]

Wide‐bandgap perovskites have attracted much attention due to their potential application in perovskite‐based tandem solar cells, which can surpass the theoretical efficiency up‐limit of single‐junction solar cells. However, photoinduced phase segregation remains one of the most intractable impediments that deteriorate the operational stability of wide‐bandgap perovskites solar cells. Herein, the effect of a series of alkali halides additives on the photoinduced phase segregation of wide‐bandgap perovskites with the composition of FA0.8Cs0.2Pb(I0.7Br0.3)3 (FA is formamidinium) is systematically studied. By coupling in situ time‐dependent photoluminescence technique, potassium chloride (KCl) is demonstrated to be the best in suppressing the photoinduced phase segregation. The reduced iodine vacancy defects owing to supplemented chloride ions and the coupling of potassium ions with the accumulated iodide ions at the grain boundaries lead to effective suppression phase segregation. As a consequence, the KCl‐modified wide‐bandgap perovskite solar cells present a champion efficiency of 19.34%, and the devices can maintain 93% of the initial efficiency after light soaking for 500 h with maximum power point tracking under 1 sun equivalent white light‐emitting diode illumination, much superior to the reference device without KCl modification only retaining 72% of its initial efficiency. [ABSTRACT FROM AUTHOR]

The corrected text is below, For ligand modification, 0.5 mg pentaerythritol tetrakis(3-mercaptopropionate) (ML) is dissolved in 1 mL CB and spun on top of perovskite, These errors do not affect the conclusions of the report. In the supporting information file of the same manuscript, on Page 2, in the "Device fabrication" an error related to the protocol for ligand modification was made. [Extracted from the article]

Flexible perovskite solar cells often experience constant or cyclic bending during their service life. Catastrophic failure of devices may occur due to the crack of polycrystalline perovskite films and delamination at the perovskite and the substrate interfaces, posing a significant stability concern. Here, a multiple dynamic hydrogen bonding polymer network is developed to enhance the mechanical strength of flexible perovskite solar cells in two ways. The main chain of poly(acrylic acid) decreases the mismatch of the coefficient of thermal expansion between the perovskite and the substrate by 16.7% through its flexibility and spatial occupation. The dopamine branch chains provide multiple dynamic hydrogen bonding sites, which contribute to increased energy dissipation upon stress deformation and reduce Young's modulus of perovskite by 54.3%. The inverted flexible perovskite solar cells achieve a champion power conversion efficiency of 23.02% and retain 81.3% of the initial PCE over 2000 h under continuous 1‐sun equivalent illumination. Moreover, devices show excellent mechanical stability by remaining 90.2% of the original value after 5000 bending cycles. [ABSTRACT FROM AUTHOR]

Controlling the perovskite morphology and defects at the buried perovskite-substrate interface is challenging for inverted perovskite solar cells. In this work, we report an amphiphilic molecular hole transporter, (2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanovinyl)phosphonic acid, that features a multifunctional cyanovinyl phosphonic acid group and forms a superwetting underlayer for perovskite deposition, which enables high-quality perovskite films with minimized defects at the buried interface. The resulting perovskite film has a photoluminescence quantum yield of 17% and a Shockley-Read-Hall lifetime of nearly 7 microseconds and achieved a certified power conversion efficiency (PCE) of 25.4% with an open-circuit voltage of 1.21 volts and a fill factor of 84.7%. In addition, 1–square centimeter cells and 10–square centimeter minimodules show PCEs of 23.4 and 22.0%, respectively. Encapsulated modules exhibited high stability under both operational and damp heat test conditions. [ABSTRACT FROM AUTHOR]

• A finely-controlled CVD deposition of hydrophobic Parylene C polymer is conducted to form the interlayer in inverted PSCs. • Parylene polymer can also serve as a wide-bandgap and insulated tunneling layer to inhibit interfacial charge recombination and benefit the charge transfer and the chloride group chemically react with the undercoordinated lead centers and decrease the defects of the device. • The Parylene C modified devices yield impressive long-term stability and reproducibility, both of which are important features urgently required by the industrialization of PSCs. Perovskite solar cells (PSCs) have been shining in the photovoltaic industry, but their fragile stability impedes their commercialization seriously. Here we adopt an ultra-thin film of a functional hydrophobic polymer, polychloro-p-dimethyl benzene (Parylene C), which can largely improve the operational lifetime of PSCs as a surface finish. Chemical vapor deposition (CVD) under vacuum is adopted to modify the ultra-thin parylene film, which is thin adequately to afford tunnel contact but is also sufficiently shielding to protect the perovskite layer. Besides, it is demonstrated that the Parylene C film can reduce the perovskite surface defects by interacting with the uncoordinated Pb center and act as an effective hole-hindering barrier in the middle of perovskite and PCBM for decreasing charge recombination. As a result, PSC using a ∼4 nm Parylene C layer exhibits a remarkably increased open-circuit and fill factor and a substantially enhanced efficiency of 21.7 % from pristine 19.4 %. Moreover, the Parylene C-based PSCs have attained long-term thermal and operational stabilities with good reproducibility. Without encapsulation, the degradation was limited to 11 % after 500 h of aging under ambient atmosphere/dark, 85 °C/N 2, or constant illumination/ N 2 conditions. This work lays a solid foundation for further stability by CVD interface modification. [ABSTRACT FROM AUTHOR]