Exploitation of next-generation blue light-emitting diodes (LEDs) is the foundation of the revolution in lighting and display devices. Development of high-performance blue perovskite LEDs is still challenging. Herein, 4-aminobenzenesulfonic acid (SA) is introduced to passivate blue CsPbBr3 nanoplates (NPLs), reducing the ionic migration via a more stable Pb2+-SO3-- formation, and the trap state density of films shows a 50% reduction. The inevitable Br- vacancy defects after the multistep washing process can be suppressed by a suitable MABr treatment, which can boost the external quantum efficiency (EQE) performance. It should be noted that the coverage of NPL films is another key factor to realize reproducible pure blue electroluminescence (EL). Therefore, we proposed an alternate droplet/spin coating method to improve the coverage and thickness of NPL layer to prevent hole transport layer emission and increase the reproducibility of LED performance and spectra. Furthermore, we designed hole transport layers to decrease the hole transport barrier and improve the energy-level alignment. According to SA passivation, MABr treatment, alternate droplet/spin coating method, and device structure optimization, a CsPbBr3 NPL-based pure blue (0.138, 0.046) LED with 3.18% maximum EQE can be achieved, and the half-lifetime of EL can be enhanced 1.71 times as compared to that of the counterpart LED without SA. Both performance and stability of pure blue NPL LEDs can be greatly improved via ligand passivation, alternate droplet/spin coating method, and device structure optimization, which is a trend to promote the development of pure blue perovskite LEDs in future.
Keywords: CsPbBr3 NPLs; alternate droplet/spin coating method; ligand passivation; perovskite LED; pure blue.