Cr3+ Doping Enhanced Photoluminescence of Nano-Sized CsPbBr3 Perovskite

Abstract

CsPbBr₃ nanocrystals (NCs) have attracted extensive attention due to their high color purity and good thermal stability. However, due to the quenching of surface defects, the photoluminescence quantum yields (PLQY) are low, and there are few previous comparative studies on the magnetic ion doping of powders and nanocrystals in this system. In this article, the effect of Cr³⁺ doping CsPbBr₃ NCs and CsPbBr₃ powders and their PL properties is investigated. The successful doping of Cr³⁺ is verified by TEM, SEM, and EDS characterization. At the appropriate amount of Cr³⁺, the PLQY of Cr³⁺ doped CsPbBr₃ NCs achieves 96%, twice that of undoped CsPbBr₃ NCs. However, the PLQY of the CsPbBr₃ powder does not change much after Cr³⁺ doping at its close emission wavelength. The electron paramagnetic resonance (EPR), temperature dependent PL and density functional theory (DFT) calculation show that the enhanced PL of doped CsPbBr₃ NCs is due to the formation of exciton magnetic polaron (EMPs), while the confined excitons in undoped NCs are multiple due to spin-orbit interaction. In CsPbBr₃ powders, both EMPs and antiferromagnetic excitons (AMPs) coexist and compete, verified by the PL decay curve, temperature variation spectra, and low temperature PL spectra in strong magnetic field.