A dual ligand synergism strategy for fabrication of highly luminescent FAPbBr3 nanocrystal films and efficient electroluminescent devices

Abstract

Perovskite light-emitting diodes (PeLEDs) have attracted widespread interest owing to their tunable emissions, high color purity and cost effective fabrication processes. It is widely recognized that high quality perovskite nanocrystal (PeNC) films are crucial for obtaining efficient PeLEDs. However, due to the fast crystallization rate of perovskite precursors, it is a great challenge to achieve precise control of the size and dimension of the PeNC film using a single ligand additive. Here, two types of ligands with different effects, phenethylamine bromide (PEABr) and benzoic acid (BZA), are together introduced for fabrication of formamidine lead bromide (FAPbBr₃) NC films. By systematically investigating the formation process of FAPbBr₃ crystals using dual ligands, the regulation mechanism and the ligand synergistic effect are revealed. Then, highly luminescent and uniform FAPbBr₃ NC films with a well confined three dimensional structure are fabricated through finely tuning the ratio of PEABr and BZA. Efficient electroluminescent (EL) devices are further achieved based on these obtained high quality FAPbBr₃ NC films with the maximum current efficiency of 39.0 cd A⁻¹ and an external quantum efficiency of 9.5%. Besides, the ligand synergistic effect on improving the device performance is explained and clarified. Moreover, EL devices fabricated using FAPbBr₃ NC films based on dual ligands exhibit a significantly prolonged operation lifetime and better adaptability for large scale displays, showing potential advantages for future LED applications.