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Two-dimensional (2D) metal halide perovskites, such as BA2SnI4(BA═CH3(CH2)3NH3), exhibit an enhanced charge carrier lifetime in experiments under strain. Experiments suggest that significant compression of the BA molecule, rather than of the inorganic lattice, contributes to this enhancement. To elucidate the underlying physical mechanism, we apply a moderate compressive strain to the entire system and subsequently introduce significant compression to the BA molecules. We then perform ab initio nonadiabatic molecular dynamics simulations of nonradiative electron–hole recombination. We observe that the overall lattice compression reduces atomic motions and decreases nonadiabatic coupling, thereby delaying electron–hole recombination. Additionally, compression of the BA molecules enhances hydrogen bonding between the BA molecules and iodine atoms, which lengthens the Sn–I bonds, distorts the [SnI6]4–octahedra, and suppresses atomic motions further, thus reducing nonadiabatic coupling. Also, the elongated Sn–I bonds and weakened antibonding interactions increase the band gap. Altogether, the compression delays the nonradiative electron–hole recombination by more than a factor of 3. Our simulations provide new and valuable physical insights into how compressive strain, accommodated primarily by the organic ligands, positively influences the optoelectronic properties of 2D layered halide perovskites, offering a promising pathway for further performance improvements.

Inorganic cesium lead triiodide perovskite has shown great potential in photovoltaic applications. Currently, the preparation of high-quality β- or γ-phase CsPbI3films largely relies on the DMAPbI3(dimethylammonium [DMA]) or “HPbI3”-assisted crystallization method, which unfortunately causes DMAPbI3residue and deteriorates photovoltaic performance and stability. Herein, a universal hydrogen-bonding-facilitated DMA extraction method is developed to fabricate high-quality γ-CsPbI3films. Theoretical and experimental evidence manifests that the hydrogen bonds formed between polyacrylic acid (PAA) and DMAPbI3decrease the DMA escape energy barrier, and this not only brings ahead the decomposition process of DMAPbI3but also accelerates the crystallization kinetics of CsPbI3, resulting in pinhole-free CsPbI3films without any trace of DMAPbI3residue and an extended fabrication humidity (up to 80% relative humidity [RH]) and temperature window. Thanks to the environmentally benign crystallization, the CsPbI3solar cells with dopant-free poly(3-hexylthiophene) (P3HT) yield a high efficiency of 20.25% and superior moisture and operational stability.