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.