Reduction of intrinsic defects in hybrid perovskite films via precursor purification.

A simple chemical process was developed in a scalable manner, to reduce trap states in perovskite absorbers from the very beginning. The obvious decrease of I in methylammonium iodide and the decrease of trap density in the resultant films were identified, which led to the power conversion efficiency (PCE) of perovskite solar cells (PSCs) increase from 16.5% to 18.5%.