Transient Dynamics of Charges and Excitons in Quantum Dot Light-Emitting Diodes.

Wide interest in quantum dot (QD) light-emitting diodes (QLEDs) for potential application to display devices and light sources has led to their rapid advancement in device performance. Despite such progress, detailed operation mechanisms of QLEDs, which are necessary for the fundamental understanding and further improvements, have been still uncertain because of the intricate interaction between charges and excitons in electrical operation. In this work, the transient electroluminescence (TREL) signals of dichromatic QLEDs which are purposely designed to consist of two different color-emitting QD layers are analyzed. As a result, not only can the charge injection and exciton recombination processes be visualized but the electron mobility of the QD layer can also be estimated. Furthermore, the effects of Förster resonant energy transfer between two QDs and exciton quenching near the QD layer are quantitatively measured in QLED operation. The authors believe that their results based on TREL analyses will contribute to the understanding and development of high-performance QLEDs.