Simultaneous Strontium Doping and Chlorine Surface Passivation Improve Luminescence Intensity and Stability of CsPbI₃ Nanocrystals Enabling Efficient Light-Emitting Devices

A method is proposed to improve the photo/electroluminescence efficiency and stability of CsPbI₃ perovskite nanocrystals (NCs) by using SrCl₂ as a co-precursor. The SrCl₂ is chosen as the dopant to synthesize the CsPbI₃ NCs. Because the ion radius of Sr²⁺ (1.18 Å) is slightly smaller than that of Pb²⁺ (1.19 Å) ions, divalent Sr²⁺ cations can partly replace the Pb²⁺ ions in the lattice structure of perovskite NCs and cause a slight lattice contraction. At the same time, Cl⁻ anions from SrCl₂ are able to efficiently passivate surface defect states of CsPbI₃ nanocrystals, thus converting nonradiative trap states to radiative states. The simultaneous Sr²⁺ ion doping and surface Cl⁻ ion passivation result in the enhanced photoluminescence quantum yield (up to 84%), elongated emission lifetime, and improved stability. Sr²⁺-doped CsPbI₃ NCs are employed to produce light-emitting devices with a high external quantum yield of 13.5%.