Fig. 1: The structure characterization for the Eu³⁺ doped CsPbCl₃ PeNCs with K⁺ ion co-doping.

a, b TEM images of Eu³⁺ doped CsPbCl₃ PeNCs without and with 15% K⁺ ion co-doping, respectively. (HTL hole transport layer, ETL electron transport layer) c Mapping images of Eu³⁺ doped CsPbCl₃ PeNCs with 15% K⁺ ion co-doping. d XRD patterns of Eu³⁺ doped CsPbCl₃ PeNCs with various K⁺ ion co-doping concentrations. e High-resolution XPS analysis corresponding to K 2p, Cl 2p, and Pb 4f for Eu³⁺ doped CsPbCl₃ PeNCs without and with 5, 20% K⁺ ion co-doping concentrations, respectively. f The diagram of the different positions occupied by K⁺ ions in perovskite. g Relative DFEs of Eu³⁺ doped CsPbCl₃ (dotted line) and Eu³⁺, K⁺ codoped CsPbCl₃. h Defect levels for both Eu³⁺ doped CsPbCl₃ and Eu³⁺, K⁺ codoped CsPbCl₃. The red lines represent the defect level introduced by Eu³⁺, whereas the blue lines represent the defect level introduced by K⁺