HONHCl optimized CHNHPbI films for improving performance of planar heterojunction perovskite solar cells via a one-step route.

Planar heterojunction perovskite solar cells (PHJ-PSCs) constructed with one-step precursor solution spin-coating deposition (OPSSD) usually give an extremely low performance mainly due to the poor morphology and low crystallinity of the perovskite films. In this work, by incorporating a suitable HONHCl additive in the perovskite precursor solution, a high quality perovskite film with improved morphology and crystallinity was obtained. The UV-vis measurement of the CHNHI solutions without and with HONHCl demonstrates that the improved quality of the perovskite film can be easily attributed to a combined effect of N, I, HO and CHNHCl originating from the oxidation of CHNHI triggered by the HONHCl additive, which can manipulate the crystallization process of the perovskite.