Spectrally Stable Blue Light-Emitting Diodes Based on All-Inorganic Halide Perovskite Films

Substantial progress has been made in perovskite light-emitting diodes (PeLEDs), but the fabrication of high-performance blue PeLEDs still remains a challenge due to its low efficiency, spectral instability and short operational lifetime. How to produce an efficient and stable blue PeLED is the key to realizing the application of PeLEDs in full-color displays. We herein report a blue PeLED usint the ligand-assisted reprecipitation method, in which phenylethylammonium bromide (PEABr) was used as ligands, and chloroform was used as anti-solvent to prepare blue perovskite nanocrystal films. By increasing the PEABr content from 40% to 100% (The ratio of x% PEABr refers to the molar ratio between PEABr and PbBr2), the film quality is highly improved, and the emission exhibits a blue shift. Introducing a poly(9-vinylcarbazole) (PVK) hole transport layer into the device, the PVK layer can not only achieve efficient hole injection, but can also isolate the PEDOT: PSS layer to inhibit the non-radiative recombination of metal halide luminescence layer, reduce surface ion defects and successfully inhibit halide atom migration. Finally, the PeLED presents a stable electroluminescence under different driving voltages without any red shift.