Unveiling Property of Hydrolysis-Derived DMAPbI for Perovskite Devices: Composition Engineering, Defect Mitigation, and Stability Optimization.

Additive engineering has become increasingly important for making high-quality perovskite solar cells (PSCs), with a recent example involving acid during fabrication of cesium-based perovskites. Lately, it has been suggested that this process would introduce dimethylammonium ((CH)NH, DMA) through hydrolysis of the organic solvent. However, material composition of the hydrolyzed product and its effect on the device performance remain to be understood. Here, we present an in-depth investigation of the hydrolysis-derived material (i.e., DMAPbI) and detailed analysis of its role in producing high-quality PSCs. By varying the ratio of CsI/DMAPbI in the precursor, we achieve high-quality CsDMAPbI perovskite films with uniform morphology, low density of trap states, and good stability, leading to optimized power conversion efficiency up to 14.3%, with over 85% of the initial efficiency retained after ∼20 days in air without encapsulation. Our findings offer new insights into producing high-quality Cs-based perovskite materials.