Unrevealing the Carrier Dynamics Behavior of Cu–In–Zn–S‐Based Quantum Dot Light‐Emitting Diodes by Transient Electroluminescence Spectroscopy

ABSTRACT The device performance of Cu–In–Zn–S (CIZS)‐based quantum‐dot light‐emitting diodes (QLEDs) still lags far behind CdSe‐based QLEDs, which mainly arise from unique trap‐related recombination in the CIZS quantum dots (QDs). Herein, the carrier dynamics behavior of CIZS‐based and CdSe‐based QLEDs was studied by transient electroluminescence (TrEL) technology, and the difference in the falling edge of the TrEL response was obviously observed in both QLEDs. The results show that Cu‐related defect states (Cu‐states) created a substantial hole injection barrier, making traditional hole‐transport layer modifications ineffective for carrier injection and transport balance. By engineering the ZnO electron transport layer (ETL), the electron injection and transport were reduced, which suppressed trap‐state‐mediated non‐radiative recombination. At last, carrier dynamics models were proposed to clarify the phenomenon of falling edge overshoot in the CIZS‐based QLEDs. This approach overcomes the intrinsic hole transport limitation in CIZS QDs caused by Cu‐states, offering a viable method to balance the carrier injection and transport without enhancing hole injection.