Advances in improved photoluminescence properties of all inorganic perovskite nanocrystals via metal-ion doping

Metal halide perovskite nanocrystals (NCs) have attracted great attention in the fields of light-emitting diodes, lasers, X-ray imaging, solar cells and photoelectric detectors due to their excellent optoelectronic properties. Compared with organic-inorganic hybrid perovskite NCs, all inorganic perovskite CsPb<i>X</i>₃ (<i>X</i> = Cl, Br, I) NCs have good photoelectric properties and high stability. To further improve the photoluminescence (PL) quantum yields (QYs) and stability of CsPb<i>X</i>₃ NCs, researchers reduced the defects as nonradiative recombination centers in NCs by the following strategies: 1) surface treatment with different ligands; 2) control of synthesis conditions with halide rich compounds; 3) doping of metal ions. Among them, metal doping is considered as a universal and effective way to adjust the optoelectronic properties of semiconductors. It is found that the type and the concentration of metal ions have great influence on the electronic band structure and PL performance of NCs after the metal ions have been doped into CsPb<i>X</i>₃ NCs. At the same time, compared with II-VI and III-V semiconductors, the unique structure of all inorganic perovskite NCs makes the doping of metal ions easier. Appropriate doping can not only enhance the intrinsic optical properties of the NCs without affecting their crystal structure, but also introduce new electronic energy levels into the NCs and new luminescent properties of doped metal ions. Based on metal ions doping strategy, the PLQYs of doped CsPb<i>X</i>₃ NCs have been enhanced to nearly 100%. In this work, we summarize recent advances in metal doping of the four typical kinds of perovskite NCs, including CsPbCl₃, CsPbBr₃, CsPbI₃, and Mn²⁺ doped CsPb<i>X</i>₃, and discuss the physical mechanisms of the improved properties through doping metal ions. It should be pointed out that the doping of some metal ions such as Ni²⁺ and Cd²⁺ into the above four kinds of NC systems can effectively passivate NC defects, thus improving the PL QY and stability of NCs. In addition, we put forward some personal perspectives on the future research subjects of interest and directions of metal doping for enhanced PL of CsPb<i>X</i>₃ NCs, which needs to be further explored in order to promote extensive application of perovskite NCs to various optoelectronic devices.