We report gas sensors based on formamidinium lead chloride (FAPbCl₃), which demonstrate a strong and outstandingly selective response towards ammonia due to the specific interaction of the halide vacancies with NH₃.

Herein, we have proposed a novel tridentate chelation strategy to manage the excessive amount of unreacted PbI ₂ in perovskite films, achieving a inverted PSC device with a PCE of 25.66% by sequential deposition method.

A critical limitation of formamidinium lead iodide (FAPbI ₃ ) perovskite solar cells (PSCs) lies in the intrinsic instability of the ionic–covalent Pb–I octahedral lattice, relative to the unfavorable hexagonal δ-phase under operating conditions. We report an entropy-regulating molecular-lock strategy using 1-pyridin-3-ylmethyl-piperazine hydrochloride (3-PMPCl). Strong interactions between the perovskite lattice surface and 3-PMPCl modulate the rotational freedom of organic cations and suppress the detrimental entropy increase associated with [PbI ₆ ] ⁴⁻ octahedra disorder or expansion. This entropy-favored environment intrinsically increases the phase transition energy barrier. The uniform distribution and strong adsorption of 3-PMPCl stabilize the α-phase under elevated temperature and humidity conditions. We achieved a certified power conversion efficiency (PCE) of 27.6% in FAPbI ₃ -based PSCs. However, the operational stability of such champion devices remains below the state of the art. Adopting a stable bismuth electrode addresses this issue with a slight reduction in efficiency, yielding a device that retains 93.0% of its initial PCE (26.8%) after 1011 hours at 85°C under 1-sun illumination.

An all-solution two-step method for preparing wide-bandgap perovskites has the advantages of low cost, good repeatability and scalability. However, achieving high-quality wide-bandgap perovskite films via an all-solution two-step method remains challenging due to uneven distribution of halogens and incomplete reactions between organic salts and inorganic salts. Herein, we introduced tris(pentafluorophenyl)borane (BCF) into an inorganic layer resulting in boron–halide bonding, which stabilized uniform halide distribution and regulated the porous structure of the lead halide films, facilitating the diffusion of organic salts. Additionally, the fluorine substituents formed hydrogen bonds with organic cations, making BCF a bifunctional additive that delayed the reaction between the organic ammonium salt and the inorganic precursor, which was conducive to the growth of large-grained perovskite crystals. During the perovskite crystallization process, BCF molecules migrated to grain boundaries and the film surface, achieving a highly positive regulation influence on the nanoscale morphology and structure of the perovskite absorber films, thus leading to a pinhole-free, stress-free and less defect perovskite films. Ultimately, the approach enabled single-junction 1.68 eV wide-bandgap perovskite solar cells with a champion efficiency of 23.49% (certified 22.73%) and a V_OC of 1.291 V. Furthermore, the optimized perovskite films were pioneeringly and successfully integrated into monolithic perovskite/silicon tandem solar cells on textured silicon and achieved an efficiency of 31.12%, which is the highest value among tandem solar cells prepared by an all-solution two-step method, retaining >90% of initial performance after 500 hours of continuous operation.