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%.