Hydrogen-bonding-facilitated dimethylammonium extraction for stable and efficient CsPbI3 solar cells with environmentally benign processing

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