Modifying the Crystal Field of CsPbCl₃:Mn²⁺ Nanocrystals by Co-doping to Enhance Its Red Emission by a Hundredfold

CsPbCl₃:Mn²⁺ is a practical solution for obtaining red-orange light inorganic perovskite nanocrystals since CsPbI₃ is unstable. Increasing the concentration of Mn²⁺ is an effective way to enhance the orange-red emission of CsPbCl₃:Mn²⁺. However, the relationship between emission intensity of the Mn²⁺ dopant and the concentration of Mn²⁺ is very chaotic in different studies. As a transition metal ion, the electronic states of Mn²⁺ are very sensitive to the crystal field environment. Here, the crystal field of the CsPbCl₃:Mn²⁺ nanocrystals was adjusted by co-doping other cations, and the concentration of Mn²⁺ remained unchanged. Additionally, the crystal field strength of different samples was calculated. Compared with the CsPbCl₃:Mn²⁺ nanocrystals, the red-orange peak in the fluorescence spectrum of CsPbCl₃:Mn²⁺, Er³⁺ nanocrystals was redshifted from 580 to 600 nm and enhanced by 100 times successfully. The same experiment was carried out on CsPbCl₃:Mn²⁺ nanoplatelets at the same time to confirm the changed crystal field around Mn²⁺. The effect of co-doping cations on the luminescence properties of Mn²⁺ is similar to that in nanocubes, and the mechanism was analyzed in detail.