Interlayer Engineering Improves Reverse Bias Stability in Halide Perovskite Photovoltaics

Reverse bias instability is a key concern for the commercialization and reliability of halide perovskite photovoltaics. Reverse bias occurs when the shaded cell in a series-connected solar panel generates less power, the remaining illuminated cells place a reverse voltage on the shaded cell, trying to push current through it in the wrong direction, which can lead to serious degradation of the shaded cell. Here we show that the choice of interlayers and device architecture engineering can improve reverse bias stability in two different scenarios. The first scenario is stabilizing perovskite solar cells under high reverse bias by reducing dark current and increasing reverse breakdown voltages, which can reduce the number of bypass diodes needed to protect a solar panel. The second scenario is stabilizing the cells when passing high reverse current (J_mpp, the current density at the maximum power point) so that perovskite solar panels can be intrinsically stable and could avoid installing bypass diodes. We systematically studied the kinetics of cell degradation under reverse voltage or reverse current conditions as a function of illumination, total injected current density, and shaded sizes. We show progress stabilizing cells under reverse current and compare the perovskite cell degradation mechanisms under high reverse bias (mild current) with that when passing high current. We suggest further mitigation strategies to tackle reverse bias challenges in both scenarios.