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