Interfacial Energy-Level Alignment for High-Performance All-Inorganic Perovskite CsPbBr₃ Quantum Dot-Based Inverted Light-Emitting Diodes

All-inorganic perovskite light-emitting diode (PeLED) has a high stability in ambient atmosphere, but it is a big challenge to achieve high performance of the device. Basically, device design, control of energy-level alignment, and reducing the energy barrier between adjacent layers in the architecture of PeLED are important factors to achieve high efficiency. In this study, we report a CsPbBr₃-based PeLED with an inverted architecture using lithium-doped TiO₂ nanoparticles as the electron transport layer (ETL). The optimal lithium doping balances the charge carrier injection between the hole transport layer and ETL, leading to superior device performance. The device exhibits a current efficiency of 3 cd A^-1, a luminance efficiency of 2210 cd m^-2, and a low turn-on voltage of 2.3 V. The turn-on voltage is one of the lowest values among reported CsPbBr₃-based PeLEDs. A 7-fold increase in device efficiencies has been obtained for lithium-doped TiO₂ compared to that for undoped TiO₂-based devices.