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Perovskite solar cells (PSCs) are exuding unique charm in the third generation of thin film solar cell technology with high power conversion efficiency (PCE) and low production cost. Recently, the lead‐free tin halide perovskite solar cells (TPSCs) have drawn significant research interests due to the advantages of low toxicity, near‐ideal bandgap and high carrier mobility. However, the rapid crystallization and easy oxidation limits the film quality and final performance of the solar cells. Therefore, the deposition of high‐quality tin halide perovskite films is key to the advance of TPSCs. In this review, the classical theory of solution nucleation and crystal growth is reviewed and correlated to the practical deposition of tin perovskite film. The physicochemical properties of tin perovskite with those of lead counterpart and the differences in the crystallization process is carefully compared. On this basis, recent regulation strategies are systematically summarized in terms of the nucleation management, intermediate phase engineering and crystal growth regulation. In addition, the preparation of mixed tin‐lead (Sn‐Pb) PSCs toward high performance is also discussed, as well as the limiting factors for device performance and stability. Finally, the future challenges and prospects of the crystallization regulation are discussed toward more efficient and stable TPSCs. [ABSTRACT FROM AUTHOR]

Recently, the emerging of low‐dimensional tin perovskite solar cells (TPSCs) by introducing bulky organic spacers has attracted extensive attention. It can not only inhibit the oxidation of Sn2+, but also reduce the ion migration and self‐doping effect. Thanks to these advantages, the TPSCs have achieved an impressive power conversion efficiency (PCE) of over 15% recently. However, the introduction of organic spacers impedes the carrier transport and thus limits the attainable PCE. Therefore, it is important to understand the carrier‐transport mechanism in low‐dimensional perovskite to develop more efficient and stable TPSCs. In this review, the latest progress of carrier transport in low‐dimensional TPSCs is summarized in detail. First, the characteristics of carrier transport in low‐dimensional tin perovskites are discussed. Then, the strategies to improve carrier transport are discussed, mainly from the aspects of crystal orientation, crystallization kinetics, defects, interface energy level alignment, quantum well effect, and exciton binding energy. Finally, the future challenges and prospects are expounded to prepare high‐performance and stable low‐dimensional TPSCs. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In recent years, X‐ray detectors have been widely applied in industrial non‐destructive testing, medical diagnostics, scientific research, and so on. CsPbX3 has become a dazzling star material because of its high X‐ray absorption coefficient, low trap density, long carrier diffusion length, and other excellent photoelectric characteristics. This review first presents the crystal structure of CsPbX3 and then systematically introduces three single crystal growth methods and two quantum dot synthesis methods. Next, the research progress of X‐ray detection is introduced for different material types and detector types. Finally, the challenges and development prospects of CsPbX3 are discussed. [ABSTRACT FROM AUTHOR]

Tin halide lead‐free perovskite solar cells (TPSCs) have received tremendous research interest recently due to their nearly ideal bandgap, broad light absorption, non‐toxicity, and environmental friendliness. However, the uncontrollable crystallization process and the facile oxidation of Sn2+ limit the further increase of power conversion efficiency (PCE). To solve these problems, a series of acetates are introduced into the perovskite precursor solution to regulate the crystallization process. It is revealed that formamidine acetate (FAAc) has strong COSn coordination with Sn2+ compared with acetic acid (HAc) and methylammonium acetate (MAAc), which can stabilize the lattice structure, minimize defect states and suppress the oxidation of Sn2+. Meanwhile, benefiting from this coordination ability, it not only leads to large‐size colloidal clusters in precursor but also slows down the crystallization process and improves the crystallinity of tin halide perovskite films. The device with FAAc achieved an increased PCE from initially 9.84% to 12.43%, and it could maintain 94% of its initial value for 2000 h in N2 atmosphere. This work provides a feasible strategy for depositing high‐quality tin perovskite films with low defect density and lattice distortion, which will be crucial for related photovoltaics and other optoelectronic devices. [ABSTRACT FROM AUTHOR]

Bulky organic cations exhibit significant roles in improving the phase stability of CsPbI3 by reducing its dimension with higher steric hindrance. However, the insulative properties of organic cations impede the carrier transition and damage the device performance. Herein, a new aromatic cation of 4‐fluorobenzenaminium (FPA+) in the 2D CsPbI3 to act as a spacer cation, is reported. Based on the theoretical simulation and experimental characterization for materials properties, film quality, and device performance, the large dipole moment and electronic inductive effect of FPA+ cations improve the hydrogen bond between H and I atoms, which is beneficial to realizing controllable crystallization quality. Therefore, the whole quality of 2D CsPbI3 film is improved with a larger grain size, compact morphology, and low trap density. As a result, the (FPA)2Cs4Pb5I16 perovskite solar cell delivers a power conversion efficiency of 15.18%, significantly higher than that of PA‐based (14.32%) perovskite solar cells. Herein, an in‐depth understanding of fluoro‐substituted organic cations is provided and is beneficial to the design and synthesis of new organic molecules in 2D perovskite. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) Ruddlesden–Popper (RP) CsPbI3 perovskite possesses superior phase stability by introducing steric hindrance. However, due to the quantum and dielectric confinement effect, 2D structures usually exhibit large exciton binding energy, and the charge tunneling barrier across the organic interlayer is difficult to eliminate, resulting in poor charge transport and performance. Here, a multiple‐ring aromatic ammonium, 1‐naphthylamine (1‐NA) spacer is developed for 2D RP CsPbI3 perovskite solar cell (PSC). Theoretical simulations and experimental characterizations demonstrate that the 2D RP CsPbI3 perovskite using 1‐NA spacer with extended π‐conjugation lengths reduces the exciton binding energy and facilitates the efficient separation of excitons. In addition, its cations have a significant contribution to the conduction band, which can reduce the bandgap, promote electronic coupling between organic and inorganic layers, and improve interlayer charge transport. Importantly, the strong π–π conjugation of 1‐NA spacer can enhance intermolecular interactions and hydrogen bonding, and prepare high‐quality films with preferred vertical orientation, resulting in lower defect density, and directional charge transport. As a result, the (1‐NA)2(Cs)3Pb4I13 PSC exhibits a record 16.62% performance with enhanced stability. This work provides an efficient approach to improve charge transport and device performance by developing multiple‐ring aromatic spacers. [ABSTRACT FROM AUTHOR]

Typically, DMSO and DMF are the two most commonly used co-solvents; however, their boiling points differ greatly and the volatilization rate is not consistent when the film is annealed and crystallized, which leads to the inhomogeneity of the components. Herein, the hydrogen isotope effect (HIE) is produced by introducing N,N-dimethylformamide-d7 (DMF-d7) into the CsPbI3 precursor solution for the first time. The introduction of deuterium affects the intermolecular interaction between the solvent molecules and Pb2+, and ameliorates the undesirable situation of excessive uncoordinated Pb2+ remaining on the surface of the film. As a result, the power conversion efficiency (PCE) of the optimized device reached 18.55%. The characterization of the film structure, morphology, and components demonstrates that the addition of DMF-d7 improves the quality of the film. More importantly, according to the apparent change in the atomic ratios of Cs and Pb (Cs/Pb), we speculate that different film crystallization rates eventually lead to two different crystallization termination surfaces, i.e., with PbI2 or CsI, and illustrate their effects on the properties of the film by ab initio simulations. Overall, this study developed a novel solvent system that provides a promising method for the fabrication of high-quality CsPbI3 films. [ABSTRACT FROM AUTHOR]