Fig. 1. Morphology and crystal structure of nanocrystals (NCs): (a), (b) TEM images of CsPbCl₃ and Cu doped CsPbCl₃ NCs, the inset shows high resolution TEM images of a single NC^[49]; (c) XRD patterns of CsPbCl₃ and Cu doped CsPbCl₃ NCs^[49].

Fig. 2. Optical properties and crystal structure of metal ion doped CsPbCl₃ NCs. (a) Absorption and PL spectra of CsPbCl₃ and Cu-doped CsPbCl₃ NCs^[49]. (b) Schematic diagram of doping models for BaCl₂ doped CsPbCl₃^[50]. PL spectra (c) and PL decay curves (d) of CsPbCl₃ NCs before and after CdCl₂ treatment. The inset in panel (c) shows the photos of untreated and treated samples under a UV lamp^[52]. (e) Band structure and DOS of Ni²⁺:CsPbCl₃ by DFT calculation. The horizontal dotted line represents the Fermi level^[53]

Fig. 3. Optical properties and crystal structure of metal ion doped CsPbBr₃ NCs: (a) Schematic illustration of Sb³⁺ doped CsPbBr₃^[57]; (b) PLQY vs. Ni²⁺ doping concentration of CsPbBr₃ NCs^[59]; (c) PLQY vs. Cu²⁺ doping concentration of CsPbBr₃ NCs; electronic band structures before (d) and after (e) of Cu²⁺doped CsPbBr₃ NCs by DFT calculations^[60]; (f) PL spectra and PLQYs before and after Mg²⁺ doping of CsPbCl₃ and CsPbBr₃ NCs^[51]

Fig. 4. Optical properties of metal ion doped CsPbI₃ NCs: (a) PLQY of CsPbBrI₂ NCs solution with different dopant concentration of Cu^2+[62]; (b) PLQY values as a function of aged days for unsubstituted and Sr²⁺-substituted CsPbI₃ NCs solutions^[63]; (c) absorption and PL spectra of as-synthesized Ni (II) doped CsPbI₃ NCs^[64]; successive PL spectra of Sb³⁺ doped (d) and undoped (e) CsPbI₃ NCs^[65]; (f) the absorption and PL peak maxima and PLQYs of CsPbI₃ NCs with different Zn-to-(Zn plus Pb) ratios^[66]

Fig. 5. Optical properties of Mn²⁺ doped CsPbI₃ NCs: (a) PL spectra and photographs under UV excitation of CsPbCl₃ NCs before and after Mn²⁺ doping^[67]; (b), (c) PL intensity and PL lifetime of Mn²⁺:CsPbCl₃ at different temperature (340 and 360 K) with different time^[69].

Fig. 6. Optical properties of CsPbX₃ NCs doped with metal ions and Mn²⁺: (a) PLQY of Mn²⁺ doped CsPbX₃ NCs vs. Ni/Pb ratios^[72]; (b) PL spectrum and PL decay curve of Mn²⁺ doped CsPbX₃ NCs after treatment with CdCl₂ solution^[73]; (c) digital photos of Mn²⁺ doped CsPbX₃ NCs before and after treatment with CdCl₂ solution under UV excitation with different purification times^[73].