Vacuum-Deposited Blue Inorganic Perovskite Light-Emitting Diodes

Perovskite light-emitting diodes (PeLEDs) have drawn great research attention because of their outstanding electroluminescence performance by solution processing. PeLEDs made by thermal evaporation are relatively rarely explored but are compatible to existing organic light-emitting diode industrial lines. Blue-emitting PeLEDs are all based on organic-containing perovskites, rather than more stable all-inorganic perovskites because of their poor solubility, too fast crystallization, uneven discrete films, and unattainable pure blue emission. Here, we report all-inorganic, vacuum-processed blue PeLEDs. High-throughput combinatorial approaches are employed to optimize Cs-Pb-Br-Cl composition in our dual-source co-evaporation system to achieve the balance between film photoluminescence and injection efficiency. The as-deposited perovskite films demonstrated excellent intrinsic stability against heat, UV-light, and humidity attack. A series of PeLEDs were obtained covering the standard blue spectral region with a best luminance of 121 cd/m² and an external quantum efficiency of 0.38%. We believe that the vacuum processing strategy demonstrated here provides a very promising alternative way to produce efficient and stable all-inorganic blue-emitting PeLEDs.