Highly stable CsPbI3:Sr2+ nanocrystals with near-unity quantum yield enabling perovskite light-emitting diodes with an external quantum efficiency of 17.1%

Removing long-chain ligands on the surface of perovskite nanocrystals (NCs) is a promising strategy to facilitate charge transport towards a high-performance perovskite light-emitting diode (PeLED). However, perovskite NCs , especially CsPbI 3 NCs, tend to decompose in the ligand removal procedure due to their poor stability of perovskite NCs and high polarity of solvents. Here, we report Sr 2+ -doped CsPbI 3 NCs that were synthesized by a modified hot injection method. These NCs show enhanced stability and near-unity photoluminescence quantum yield (PLQY, 99.8%). More importantly, the CsPbI 3 :Sr 2+ NCs still maintain a high PLQY (97.5%) after removing surface ligands by a polar solvent (ethyl acetate, EA). Furthermore, a mixture of EA and octane was used to prepare smooth and dense CsPbI 3 :Sr 2+ NC films with an exceedingly high PLQY of 73.2% and a high stability under ambient conditions. Finally, the red-emitting CsPbI 3 :1.8% Sr 2+ PeLEDs demonstrate a world-record peak external quantum efficiency (EQE) of 17.1%.