Interfacial engineering of quantum dots with PMMA for performance-enhanced light-emitting metal-insulator-semiconductor junction

Quantum dots (QDs)-based light-emitting metal-insulator-semiconductor junction (LE-MISJ) devices currently face challenges of low brightness and short lifetime. The degradation mechanisms of the device remain poorly understood. In this work, to explore carrier dynamics and QDs degradation mechanism in the QDs layer, we construct a LE-MISJ device consisting of electrode/insulator/monolayer QDs/electrode to investigate its photoelectric properties. It is found that continuous carrier injection and carrier transport between QDs lead to electric field-induced dielectric breakdown between QDs, accelerating the formation of defects on the surface of QDs and leading to QD degradation. Experimental and theoretical analyses demonstrate that filling the QDs gap with poly(methyl methacrylate) (PMMA) effectively protects and supports surface ligands and reduces carrier-induced damage. The device with 2% PMMA shows 180% enhanced peak electroluminescence intensity and spectral narrowing (full width at half maximum from 38.8 nm to 31.2 nm) compared to PMMA-free controls. Moreover, the device with 2% PMMA decays to 80% of the original intensity in 4.5 times the time of the device without PMMA. This study can provide some research value to understand the working principle and optimization of LE-MISJ.