Highly Efficient Vacuum-Evaporated CsPbBr₃ Perovskite Light-Emitting Diodes with an Electrical Conductivity Enhanced Polymer-Assisted Passivation Layer

Abstract

Highly efficient vacuum-deposited CsPbBr₃ perovskite light-emitting diodes (PeLEDs) are demonstrated by introducing a separate polyethylene oxide (PEO) passivation layer. A CsPbBr₃ film deposited on the PEO layer via thermal co-evaporation of CsBr and PbBr₂ exhibits an almost 50-fold increase in photoluminescence quantum yield intensity compared to a reference sample without PEO. This enhancement is attributed to the passivation of interfacial defects of the perovskite, as evidenced by temperature-dependent photoluminescence measurements. However, direct application of PEO to an LED device is challenging because of the electrically insulating nature of PEO. This issue is solved by doping PEO layers with MgCl₂. This strategy results in an enhanced luminance and external quantum efficiency (EQE) of up to 6887 cd m^-2 and 7.6%, respectively. To the best of our knowledge, this is the highest EQE reported to date among vacuum-deposited PeLEDs.