In Situ Passivation of Two-Dimensional Perovskites by External Electric Field

The outstanding performance of halide perovskite makes it one of the champion materials for applications in optoelectronic devices. However, the stability of perovskites limits their practical applications. Among all the factors influencing the stability of perovskites, defects are one of the key factors. Till now, many chemical methods have been proposed to passivate defects. Nevertheless, there is still a lack of in situ passivation methods without the change of the composition of perovskites. Here, it is found that the external electric field can passivate the defects in FPEA(2)PbI(4) (FPEAI = 2-(4-Fluorophenyl)ethylamine Hydroiodide) film in a capacitive device at 78 K, and the PL intensity can be enhanced greatly. A "charge-soaking effect" can be observed, that is PL intensity continues to increase for a long time after removing the electric field. Besides the emission peak from free exciton, two other peaks at the lower energy side from defect-bound excitons are observed. They are more susceptible to the external electric field than the free exciton. This work will deepen the understanding of exciton behavior and the interaction of electric field with excitons in two-dimensional (2D) hybrid perovskites for efficient light-emitting diodes (LEDs) and electrically pumped lasers. It provides a new in situ passivation method of perovskites for practical applications.