Unveiling the Effects of Hydrolysis‐Derived DMAI/DMAPbI x Intermediate Compound on the Performance of CsPbI 3 Solar Cells

Introducing hydroiodic acid (HI) as a hydrolysis‐derived precursor of the intermediate compounds has become an increasingly important issue for fabricating high quality and stable CsPbI 3 perovskite solar cells (PSCs). However, the materials composition of the intermediate compounds and their effects on the device performance remain unclear. Here, a series of high‐quality intermediate compounds are prepared and it is shown that they consist of DMAI/DMAPbI x . Further characterization of the products show that the main component of this system is still CsPbI 3 . Most of the dimethylammonium (DMA + ) organic component is lost during annealing. Only an ultrasmall amount of DMA + is doped into the CsPbI 3 and its structure is stabilized. Meanwhile, excessive DMA + forms Lewis acid–base adducts and interactions with Pb 2+ on the CsPbI 3 surface. This process passivates the CsPbI 3 film and decreases the recombination rate. Finally, CsPbI 3 film is fabricated with high crystalline, uniform morphology, and excellent stability. Its corresponding PSC exhibits stable property and improved power conversion efficiency (PCE) up to 17.3%.