Additive Screening for Suppressing Light-Induced Phase Segregation and Ionic Activity in Halide Perovskite Devices

Devices made from mixed halide perovskites are prone to halide segregation due to ionic migration under light illumination, limiting their applications. Additive engineering to suppress ionic migration has emerged as a prominent strategy to counter this effect. Herein, utilizing a high-throughput platform, five different additives─KI, RbBr, Rb₂CO₃, TBABF₄, and GAI─are tracked for their effect in suppressing phase segregation across the compositional gradient of MAPb(Br_xI_1-x)₃. The influence of certain additives like tetrafluoroborate and potassium iodide in reducing ionic migration across the compositional gradient is found to be selective, whereas additives like guanidinium iodide and rubidium-based ones consistently suppress ionic migration tendency across the compositional gradient. These findings are utilized to tune the ionic migration tendencies in switchable photovoltaic and memristor applications. Lateral memristors of MAPb(Br_0.5I_0.5)₃ exhibited a hysteresis index [HI] of 0.50 at 0.26 V/μm, compared to 0.64 for KI-added devices and a much lower HI of 0.036 for GAI-added devices. This indicates a higher ionic migration tendency for KI added devices and suppressed ionic migration for GAI devices. This screening approach could also have implications for perovskite optoelectronic devices such as solar cells and LEDs, where phase and ionic stability are key to device performance.