Nanoscale Dynamic Recombination Zone Shifts in Perovskite LEDs Resolved via High-Speed Angular Profiling

Abstract The accurate determination of the external quantum efficiency (EQE) from directional radiance in perovskite LEDs (PeLEDs) relies on the assumption that the angular emission pattern remains static during operation. Here, we show that this assumption can break down in PeLEDs because slow ion/charge redistribution at charge-transport-layer/perovskite interfaces changes the nanoscale recombination-zone position. Using a custom-designed high-speed - angular profiling system, we resolve angle-dependent electroluminescence (EL) transients that are invisible to conventional sequential goniometry. Crucially, we show that applying a static angular profile to directional-radiance-based EQE calculations leads to relative errors of up to 33%. These findings establish time-resolved angular profiling as critical for accurate benchmarking and mechanistic analysis of mixed ionic-electronic light-emitting devices.