Vacuum Processed Metal Halide Perovskite Light-Emitting Diodes

Metal halide perovskite light-emitting diodes (PeLEDs) are expected to be the next-generation display technology due to their unique optoelectronic properties. Currently, the external quantum efficiencies of PeLEDs based on solution-processed fabrication methods already exceed 20%. However, there are still many challenges existing in solution-based PeLEDs that inhibit their commercialization. Recently, vacuum deposition techniques of perovskites have drawn much attention because of the ability to grow dense and uniform large-area perovskite films with precisely controlled thickness, which is compatible with state-of-the-art organic LED manufacturing processes. Despite the promising prospects of vacuum-based PeLEDs, some challenges remain to be addressed to achieve PeLEDs with both high efficiency and high stability that are required for practical applications such as active-matrix displays. This requires precise control of the film morphology, composition, and interface during the deposition process through fine-tuning of the substrate temperature, deposition rate, vacuum level, precursor formulation, and post-treatment conditions. In this review, it focuses on the key requirements for vacuum-processed PeLEDs, highlights the recent advances in materials and devices of PeLEDs, and emphasize vacuum evaporation methods as well as the corresponding device performance. Possible approaches to improve the efficiency and the long-term operational stability of vacuum-processed PeLEDs are discussed.