Partial Ligand Stripping from CsPbBr₃ Nanocrystals Improves Their Performance in Light-Emitting Diodes

Halide perovskite nanocrystals (NCs), specifically CsPbBr₃, have attracted considerable interest due to their remarkable optical properties for optoelectronic devices. To achieve high-efficiency light-emitting diodes (LEDs) based on CsPbBr₃ nanocrystals (NCs), it is crucial to optimize both their photoluminescence quantum yield (PLQY) and carrier transport properties when they are deposited to form films on substrates. While the exchange of native ligands with didodecyl dimethylammonium bromide (DDAB) ligand pairs has been successful in boosting their PLQY, dense DDAB coverage on the surface of NCs should impede carrier transport and limit device efficiency. Following our previous work, here, we use oleyl phosphonic acid (OLPA) as a selective stripping agent to remove a fraction of DDAB from the NC surface and demonstrate that such stripping enhances carrier transport while maintaining a high PLQY. Through systematic optimization of OLPA dosage, we significantly improve the performance of CsPbBr₃ LEDs, achieving a maximum external quantum efficiency (EQE) of 15.1% at 516 nm and a maximum brightness of 5931 cd m^-2. These findings underscore the potential of controlled ligand stripping to enhance the performance of CsPbBr₃ NC-based optoelectronic devices.