High-Efficiency Pure Red CsPbI₃ QLEDs Via Strong Electron Affinity Interface Layer Engineering

Inorganic perovskite quantum dots (QDs) have garnered significant attention due to their outstanding optical properties. However, perovskite quantum dot light-emitting diodes (Pe-QLEDs) still face challenges related to their fluorescence efficiency and electron injection. First, the electron transport layer (ETL) leads to severe non-radiative recombination due to fluorescence quenching in CsPbI₃ QDs. Second, there is an electron injection imbalance resulting from low electron injection efficiency, leading to reduced non-radiative recombination and external quantum efficiency. To address these issues, this study introduces two interface layer materials with different electron affinities, 1,3,5-Tris(3-pyridyl-3-phenyl)benzene (TmPyPB) and 2,4,6-Tris(3′-(pyridine-3-yl)biphenyl-3-yl)-1,3,5-triazine (TmPPPyTz). These materials not only passivated defects on the surface of CsPbI₃ QDs films but also effectively prevented the fluorescence quenching of CsPbI₃ QDs by the PO-T2T (ETL). TmPPPyTz, with a relatively lower LUMO energy level, further improved energy level matching, significantly enhancing electron injection efficiency. Ultimately, using interface engineering with the TmPPPyTz interface layer, the devices achieved an outstanding 25.80% champion-level external quantum efficiency (EQE) for Pe-QLEDs with only a sub-bandgap voltage of 1.7 V and half-life (T₅₀) is 17.99 h at 100 nits. This research provided an effective method to enhance the performance of CsPbI₃ Pe-QLEDs, addressing long-standing issues inhibiting their efficiency.