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 CsPbI3 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 Sr2+-doped CsPbI3 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 CsPbI3:Sr2+ 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 CsPbI3:Sr2+ NC films with an exceedingly high PLQY of 73.2% and a high stability under ambient conditions. Finally, the red-emitting CsPbI3:1.8% Sr2+ PeLEDs demonstrate a world-record peak external quantum efficiency (EQE) of 17.1%.