Elucidating the Impact of Electron Accumulation in Quantum-Dot Light-Emitting Diodes

Quantum-dot (QD) light-emitting diodes (QLEDs) are promising candidates for future display technology. An imbalance in the injection of electrons and holes into QLEDs leads to the accumulation of excess charges, predominantly electrons, in the QDs. The precise effects of these accumulated electrons have not yet been fully quantified. This study examines how electron accumulation affects QLED efficiency by operating multiple QLEDs at the same voltage and analyzing the correlation between device efficiency and the number of accumulated electrons, as measured by using electrically pumped transient absorption technology. We analyzed 186 QLED devices made with QDs of different colors and quantum yields. Our results show that when QLEDs utilize QDs with a quantum yield of 95%, electron accumulation indeed reduces device efficiency. However, in QLEDs using QDs with a quantum yield below 70%, a higher density of accumulated electrons enhances the device efficiency.