Retarding efficiency loss upon scaling in perovskite photovoltaics as fill factor becomes the bottleneck

Perovskite solar cells approach crystalline-silicon efficiencies at small areas, yet substantial performance losses during scale-up hinder their translation into practical modules. Here we quantify the contributions of device-performance parameters to efficiency loss during scale-up across diverse perovskite technologies, identifying fill factor ( FF F F ) as a major contributor and target for mitigating this loss. Further analysis resolves the FF deficit into voltage-, diode-non-ideality- and transport-associated contributions. Cryo-controlled processing provides an experimental route to preserve FF F F by regulating intermediate-phase evolution during crystallization. The resulting FF F F -preservation advantage arises predominantly from reduced diode non-ideality, with the other contributions being smaller. This advantage increases across device scales. A mini-module (19.48 cm 2 aperture) achieves a record certified steady-state efficiency of 23.9% with an FF F F of 83.3%, the highest reported for perovskite modules. The same FF F F limitation governs operational performance decay, linking efficiency retention during scale-up with long-term stability. Together, these results establish FF F F preservation and the factors governing it as central to mitigating performance loss during scale-up and operation.