Modulating the nonlinear optical properties of MAPbBr₃ by metal ion doping

The unique advantages of perovskites make them excellent candidates for high performance nonlinear optical devices. However, the toxicity of Pb ions restricts their further applications. The realization of Pb-free or Pb-less perovskites is an important strategy to reduce the toxicity of Pb ions. Here, we substitute the Pb ions in perovskites with Zn ions and Bi ions. Zn-doped MAPbBr₃ and Bi-doped MAPbBr₃ with varying doping concentrations were synthesized. UV-visible absorption, X-ray diffraction and X-ray photoelectron spectroscopy patterns were utilized to verify the successful metal ion doping. Utilizing the Z-scan technique, the nonlinear absorption, nonlinear refraction, and optical limiting properties of MAPbBr₃ before and after doping were studied. The results revealed an improvement in these properties following the doping process. Four-level models were put forward to elucidate the underlying mechanisms, which may be related to the changes in the type of defects after metal ion doping. This work promotes the applications of Pb-less perovskites in nonlinear optics.