Degradation and self-healing of halide perovskites exposed to vacuum thermal evaporation environment

Vacuum thermal evaporation (VTE) is widely used to deposit charge-transport layers and electrodes for halide-perovskite optoelectronics, yet its thermodynamic compatibility with perovskite semiconductors is often assumed rather than directly examined. Here, we show that the VTE environment is not passive but instead establishes competing damage and recovery kinetics. We find that short-term exposure to broad-spectrum thermal radiation under high vacuum rapidly generates an iodide-deficient, trap-rich near-surface region, leading to pronounced non-radiative recombination and degraded light-emitting diode performance. We further reveal that this perturbation is strongly surface weighted. In contrast, extending the high-vacuum dwell time enables partial re-equilibration of the radiation-damaged near-surface region, accompanied by substantial recovery of carrier lifetime, electroluminescence intensity, and device stability. These results redefine VTE as an active processing environment and identify vacuum residence time as a practical process variable for defect management in iodide-based perovskite optoelectronics.