Destructive Reverse Bias Pinning in Perovskite/Silicon Tandem Solar Modules Caused by Perovskite Hysteresis under Dynamic Shading

We demonstrate how perovskite hysteresis can result in permanent reductions in power output in perovskite/silicon tandem modules - including irreversible hotspot-induced damage - from only brief periods of shading. We show that reverse bias events in which a perovskite cell is biased above a threshold voltage - which in this work we find to be as low as -1.1 V - produces a temporary reduction in power output that is of sufficient magnitude to keep the cell pinned in reverse bias after the shading event ends. As a hysteretic phenomena, this crucial failure mode may be overlooked by static models of perovskite-based solar cells. Higher reverse bias voltages exacerbate the temporary reduction in short-circuit photocurrent, which is also sensitive to the level of illumination under reverse bias. Numerical device modelling demonstrates that this effect is consistent with our understanding of perovskite hysteresis as a consequence of mobile ion-electron coupling controlling rates of non-radiative recombination over time. Measurements of the dynamic response of single-junction perovskite cells are extrapolated to two-terminal and four-terminal perovskite/silicon tandem module modelling. We validate these models with measurements from an equivalent electronic circuit that represents a two-terminal perovskite-silicon tandem mini module. Two module-level solutions are discussed that address this issue, which includes increasing the number of bypass diodes and choosing better suited silicon bottom cells with higher shunter resistance in two-terminal tandem modules.