Simultaneous Strontium Doping and Chlorine Surface Passivation Improve Luminescence Intensity and Stability of CsPbI 3 Nanocrystals Enabling Efficient Light‐Emitting Devices

A method is proposed to improve the photo/electroluminescence efficiency and stability of CsPbI 3 perovskite nanocrystals (NCs) by using SrCl 2 as a co‐precursor. The SrCl 2 is chosen as the dopant to synthesize the CsPbI 3 NCs. Because the ion radius of Sr 2+ (1.18 Å) is slightly smaller than that of Pb 2+ (1.19 Å) ions, divalent Sr 2+ cations can partly replace the Pb 2+ ions in the lattice structure of perovskite NCs and cause a slight lattice contraction. At the same time, Cl − anions from SrCl 2 are able to efficiently passivate surface defect states of CsPbI 3 nanocrystals, thus converting nonradiative trap states to radiative states. The simultaneous Sr 2+ ion doping and surface Cl − ion passivation result in the enhanced photoluminescence quantum yield (up to 84%), elongated emission lifetime, and improved stability. Sr 2+ ‐doped CsPbI 3 NCs are employed to produce light‐emitting devices with a high external quantum yield of 13.5%.