Enhancing Efficiency and Stability of Hot Casting p-i-n Perovskite Solar Cell via Dipolar Ion Passivation

Anionic and cationic defects are considered as one of the crucial factors that affect carrier transport property and degradation of perovskite photovoltaic materials. Herein, we demonstrate a simple passivation of hot casted perovskite film in air by a dipolar ion, 2-thiophene ethylammonium chloride (TEACl), showing enhanced power conversion efficiency (PCE) of solar cell from 15.44% to 18.84% with increased open circuit voltage (V-oc) by 50 mV. The dipolar ion of TEACl can simultaneously passivate both cationic and anionic defects. Space charge limited current model, Urbach energy analysis, and photoluminescence spectroscopy were conducted and revealed that the defects passivated by TEACl reduced the defects density of perovskite films, nonradiative recombination, and electronic disorder. In addition, the device with TEACl passivation exhibited outstanding stability of power output (<0.1% decay) as compared with the device without passivation (>8% decay) from the 300 s measurement of current verse time plots (J-T plots) at 65% relative humidity and 50 degrees C in air. The 80% of initial PCE was maintained after 700 h storage. As compared to conventional passivation approaches which are typically carried out at complicated crystallization step of perovskite, this post-treatment process can be easily done on the crystallized perovskite film. This facile approach is upscale and compatible with conventional coating techniques such as slot-die coating, spray, etc. for high-quality perovskite film.