Carrier Dynamics Modulated by Hole Transport Layers in Perovskite Light-Emitting Diodes

Perovskite light-emitting diodes (PeLEDs) have made remarkable progress in recent years, establishing themselves as promising candidates for next-generation lighting and display technologies. Nevertheless, conventional cascaded hole transport layers remain constrained by critical problems related to energy level alignment, solvent orthogonality, and interfacial defect control, hindering further improvements in device efficiency and operational stability. In this work, we present an optimized cascaded hole transport structure employing [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) and poly(9-vinylcarbazole) (PVK), which simultaneously enhances hole injection efficiency and suppresses the ineffective passage of electrons. The 2PACz layer substantially reduces the hole injection barrier at the ITO/PVK interface while mitigating luminescence quenching. By implementing this optimized structure, we demonstrate a green PeLED (at 511 nm) achieving a peak external quantum efficiency of 19.34%. Furthermore, through transient electroluminescence (TrEL) measurements, we investigated carrier dynamics in both single-layer and cascade-type hole transport layers. The results reveal significant correlations between TrEL characteristics and layer configurations, providing insights into the origin of EL overshoot phenomena observed during device operation.