Enhancing the efficiency of ZnSeTe-based quantum-dot light-emitting diodes by manipulating charge dynamics

In conventional Cd-based quantum-dot light-emitting diodes (QLEDs), a reduced hole-injection barrier at the hole transport layer (HTL)–quantum-dot (QD) interface generally leads to enhanced device efficiency. However, this principle does not extend to the emerging class of environmentally friendly ZnSeTe blue QLEDs. In this work, we systematically examine the charge dynamics in ZnSeTe-based blue QLEDs, with particular focus on trap states, energy level alignment, and charge transport properties. Our findings reveal significant carrier accumulation at the ZnSeTe/ZnO interface, where emission quenching by ZnO substantially degrades device performance. To mitigate this issue, we introduce Mg-doped ZnO combined with an HTL featuring a shallow highest occupied molecular orbital level, thereby optimizing charge distribution across the device. Simulations corroborate that electrons and holes predominantly accumulate at the QD/HTL interface under this design. As a result, the efficiency of the ZnSeTe blue QLED is markedly improved, increasing from 2.1% to 6.3%. This study elucidates the critical influence of hole dynamics in ZnSeTe blue QLEDs and underscores the essential role of tailored charge management for high-performance QLED operation.