Bright and spectrally stable pure-red CsPb(Br/I)3 quantum dot LEDs realized by synchronous device structure and ligand engineering

All-inorganic CsPbBrxI3−x perovskite quantum dots (PQDs) show great potential for pure-red light-emitting diodes (LEDs). However, spectral instability caused by ion migration at high electric fields and lower luminance limit its practical applications. Here, the ITO/ZnO/PEI/CsPbBrxI3−x PQDs/N, N, N-tris (4-(9-carbazolyl) phenyl) amine (TCTA) (3 nm)/1-bis [4-[N, N-di(4-tolyl)amino]-phenyl]-cyclohexane (TAPC)/MoO3/Au device structure is first designed to reduce the overall operating voltage of the device by enhancing hole injection and transport, effectively avoiding ion migration under high electric fields, and then by post-treating CsPbBrxI3−x PQDs with n-octylphosphonic acid: K to remove surface defects and increase the activation energy of halogen migration, further suppressing ion migration while improving the optical properties of the material. Ultimately, the color-stable pure-red perovskite LED achieved a high luminance of 13730 cd m−2 at voltages as low as 4.9 V and a maximum EQE of 16.7%.