Enhancing the Performance of Quasi-Two-Dimensional Perovskite-Based Pure Red Light-Emitting Diodes through Interface Engineering with CsPbCl ₃ Quantum Dots

To optimize charge carrier injection and reduce interfacial losses in perovskite light-emitting diodes (PeLEDs), we introduced a thin interfacial layer of CsPbCl₃ quantum dots (QDs) between the red quasi-two-dimensional (PEA₅NMA₅)_0.2CsPb₂I₇ emitting layer and the electron transport layer (ETL). This interlayer markedly enhances the device performance, which we attribute to multiple synergistic effects. First, the structural compatibility between CsPbCl₃ QDs and emitters enables a seamless interface, improving film morphology and interfacial contact. Second, the CsPbCl₃ QDs serve as a passivation layer that mitigates surface trap states and suppresses iodine ions diffusion and halide vacancy-induced nonradiative recombination in emitter. Additionally, the wide bandgap and suitable conduction band position of CsPbCl₃ QDs create a favorable energy-level cascade, facilitating efficient electron injection from ETL into the emitting layer while simultaneously blocking holes. These combined effects result in enhanced electroluminescence efficiency and improved operational stability. As a result, pure red PeLEDs achieve an impressive external quantum efficiency of 23.7% as well as a 15-fold increase in operational life.