Unified Analysis of Transient Electroluminescence in Organic Light-Emitting Diodes: Deciphering Charge Transport and Emission Dynamics

초록

Understanding charge transport and recombination dynamics in organic light-emitting diodes (OLEDs) is essential for improving their optoelectrical performance. Thus, this study investigates transient electroluminescence (Tr-EL) in OLEDs using six phosphorescent emitters within both single-host and exciplex-host OLED systems. The Tr-EL responses are categorized into three types: Initial overshoot, terminal overshoot, and negligible overshoot, each corresponding to distinct physical mechanisms, i.e., trap-assisted release, charge redistribution, and efficient recombination, respectively. Time-dependent drift-diffusion simulations reproduce these behaviors and clarify the roles of mobility imbalance, interfacial accumulation, and trap density. 2D and 3D contour maps of the overshoot demonstrate a sharp, non-monotonic dependence on carrier mobilities, enabling the prediction of charge imbalance and emission dynamics. This unified experimental-theoretical framework establishes Tr-EL as a comprehensive diagnostic tool, guiding the rational design of OLEDs to suppress parasitic charge storage, enhance recombination balance, and improve optoelectrical performance.

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