Double Electron Transport Layer and Optimized CsPbI3 Nanocrystal Emitter for Efficient Perovskite Light-Emitting Diodes

Improved device performance of perovskite light-emitting diodes (LEDs) is demonstrated through the synergistic effect of the optimized CsPbI3 nanocrystals (NCs) as the emissive layer (EML) and ZnO/C60 bilayer as electron transport layers (ETLs). The optical characteristics of the CsPbI3 NCs were optimized by strictly controlling the feeding ratio of Cs:Pb:I to 1:1:3 in the synthesis processes of NCs, which leads to enhanced photoluminescence quantum yields (PL QY) from 65% to 92%. Additionally, the introduction of C60 not only optimized the energy level structure of the device, leading to more balanced charge injection and transport, but also smoothed the surface of the ZnO film and perovskite NCs. Consequently, a peak external quantum efficiency (EQE) of 10.7% and maximum luminance of 1377 cd m–2 were achieved.