High-performance thermally-evaporated light-emitting diodes via one-step vapor purification

Purity has been fundamental to the fabrication of high-performance semiconductors, spanning from precursors to reaction atmospheres. Emerging thermally evaporated perovskites involving precise control impose even stricter requirements on the purity of the vapor atmosphere. Compared to the purified solvent for the reaction atmosphere in the solution-based method, efficient and effective vapor purification remains unexplored. Here, we report one-step vapor purification for a pure atmosphere with less than one percent detrimental impurity. The in-situ residual gas analysis was employed to emphasize the complexity of the gas-phase composition and reveal the impurity reaction competition during the purification. The pre-control of the vapor atmosphere enabled a record external quantum efficiency over 20% for a thermally-evaporated perovskite light-emitting diode (PeLED) based on defect-suppressed FA_xCs_1-xPbBr₃ films. Moreover, the PeLED display panels exhibit over 5-fold and 2-fold magnification in operational and storage stability. The stability extension in OLEDs by this strategy demonstrates its universal effectiveness and commercialization potential for other types of thermally evaporated optoelectronic devices.