Electron Transport in Quantum Dot Light‐Emitting Diodes

Despite extensive research on quantum dot light‐emitting diodes, the underlying charge transport mechanisms remain poorly understood. Previously, we have demonstrated that the hole transport in quantum dot (QD) thin films is trap‐free and space‐charge‐limited. However, the electron transport mechanism remains unexplored. In this study, we systematically investigate the electron transport in red, green, and blue (RGB) core/multi‐shell QD thin films through the analysis of the current density‐voltage ( J–V ) measurements using single‐carrier devices. Our findings reveal that the electron transport in these QD thin films is significantly impeded by the presence of electron traps, which exhibit a Gaussian energy distribution within the bandgap. Notably, the electron trap distributions observed across different QD systems exhibit a high degree of similarity. Specifically, these traps have a concentration of ∼1 × 10 23 m −3 , with the trap center energy level positioned at approximately 4.0 eV below the vacuum level. Furthermore, the width of the energy distribution of the trapping sites is comparable to that of the QD transport sites. By correlating the surface‐to‐volume ratio with the number of traps, we propose that the traps are located at the core‐shell interface and arise from uncoordinated atoms. Therefore, increasing the core size can effectively suppress the trapping effect.