HONH₃Cl optimized CH₃NH₃PbI₃ 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 HONH₃Cl additive in the perovskite precursor solution, a high quality perovskite film with improved morphology and crystallinity was obtained. The UV-vis measurement of the CH₃NH₃I solutions without and with HONH₃Cl demonstrates that the improved quality of the perovskite film can be easily attributed to a combined effect of N₂, I₂, H₂O and CH₃NH₃Cl originating from the oxidation of CH₃NH₃I triggered by the HONH₃Cl additive, which can manipulate the crystallization process of the perovskite. Accordingly, the improved performance for the HONH₃Cl-induced PHJ-PSCs can also be demonstrated. At the optimized molar ratio of 1 : 1 : 0.1 for PbI₂ : CH₃NH₃I : HONH₃Cl, the PHJ-PSCs exhibit an average power conversion efficiency (PCE) of 10.61 ± 0.51%, which is much higher than that of pristine 1 : 1 : 0 based cells without additive (7.21 ± 0.61%), and the best performing HONH₃Cl-induced device can yield a PCE as high as 11.12% with a J_sc of 18.42 mA cm^-2, V_oc of 0.95 V and FF of 0.63. Introducing suitable HONH₃Cl as an additive into the perovskite precursor solution is really an effective route to enhance the performance of the PHJ-PSCs via OPSSD.