In-Situ passivation of mixed-halide perovskite nanocrystals for high-performance blue light-emitting diodes

In halide perovskite nanocrystals (NCs), insulating long chain ligands such as oleic acid (OA) and oleylamine (OAm) often remove the halide ions during the purification process, leading to surface vacancy defects. This hinders their application in light-emitting devices. Herein, we report an in-situ passivation strategy using ethyl trifluoroacetate, which is hydrolyzed to trifluoroacetic acid, as an antisolvent in the purification process to passivate defects by reacting with uncoordinated Pb2+ and OAm on the surface of NCs, thus anchoring Br− to the surface of NCs. This achieves a mild removal of OAm and OA while passivating both anionic and cationic vacancies. Consequently, we achieved high-performance blue perovskite light-emitting diodes (PeLEDs). The PeLEDs based on these NCs exhibit pure blue electroluminescence at 463 nm with an external quantum efficiency of 4.14 % and a luminance of 1035 cd m−2. This study provides insights and a foundation for the development of high-performance PeLEDs.