Iodine Electrochemistry Dictates Voltage-Induced Halide Segregation Thresholds in Mixed-Halide Perovskite Devices

摘要

Owing to straightforward stoichiometry–bandgap tunability, mixed-halideperovskites are ideal for many optoelectronic devices. However, unwantedhalide segregation under operational conditions, including light illuminationand voltage bias, restricts practical use. Additionally, the origin of voltageinducedhalide segregation is still unclear. Herein, a systematic voltagethreshold study in mixed bromide/iodide perovskite devices is performed andleads to observation of three distinct voltage thresholds corresponding to thedoping of the hole transport material (0.7 ± 0.1 V), halide segregation (0.95 ±0.05 V), and degradation (1.15 ± 0.05 V) for an optically stable mixed-halideperovskite composition with a low bromide content (10). These empiricalthreshold voltages are minimally affected by composition until very Br-richcompositions, which reveals the dominant role of iodide/triiodide/iodineelectrochemistry in voltage-induced Br/I phase separation and transport layerdoping reactions in halide perovskite devices.