Highly bright and low turn-on voltage CsPbBr₃ quantum dot LEDs via conjugation molecular ligand exchange

All-inorganic CsPbBr₃ perovskite quantum dots (QDs) hold great promise as candidate materials for next-generation electroluminescent displays owing to their excellent optoelectronic properties. However, the long insulating ligands on the surface of CsPbBr₃ QDs originating from the synthesis process hinder the fabrication of high-performance optoelectronic devices. Herein, an efficient ligand-exchange route is proposed with the use of perovskite-precursor-based halide ligands, including a series of phenalkylammonium bromides with a π-conjugation benzene ring and different branch lengths. Based on the ligand-exchange method, the conductivity of the CsPbBr₃ QD layer is significantly improved owing to ligand shortening and the insertion of the π-conjugation benzene ring. As a result, high brightness (up to 12, 650 cd/m²) and low turn-on voltage (as low as 2.66 V) can be realized in CsPbBr₃ QD light-emitting diodes (QLEDs), leading to dramatic improvements in device performance with a current efficiency of 13.43 cd/A, power efficiency of 12.05 lm/W, and external quantum efficiency of 4.33%.