Flash Surface Treatment of CH3NH3PbI3 Films Using 248 nm KrF Excimer Laser Enhances the Performance of Perovskite Solar Cells

For perovskite solar cells (PSCs), the surface traps of perovskite films have great influence on the charge carrier behavior at the interface of perovskite and charge transport layers. In this investigation, a 248 nm KrF excimer laser with high photon energy and shallow penetration depth is introduced to perform surface modification on the CH 3 NH 3 PbI 3 film through irradiation for reducing its surface trap density for the first time. A whole excimer laser surface modification (ELSM) process can be completed in few seconds, and the actual interaction time of the excimer laser and perovskite film is only several hundred nanoseconds. After ELSM, the trap density of the CH 3 NH 3 PbI 3 film decreases from 1.61 × 10 16 cm −3 to 5.81 × 10 15 cm −3 , and the nonradiative recombination is suppressed effectively. As a result, the open‐circuit voltage and the power conversion efficiency (PCE) of CH 3 NH 3 PbI 3 ‐based PSCs increase from 1082 ± 27 to 1117 ± 16 mV and from 16.69% ± 0.77% to 18.50% ± 0.65%, respectively, and the PCE of the champion device reaches 19.38%. In addition, the measured larger charge recombination resistance, slower open‐circuit photovoltage decay, and longer charge recombination lifetime confirm the effective suppression effect of ELSM on the charge carrier recombination in PSCs.