Temperature-dependent Mn²⁺ emission in codoped CsPb₂ (BrCl)₅ perovskite nanocrystals

We prepared codoped CsPb₂(BrCl)₅ nanocrystal (NC) films by varying the Cu/Mn molar ratio using a facile two-step solution method. The Mn²⁺ emission peak is studied in the temperature range of 80-300 K. Strong electron-optical-phonon coupling causes an anomalous blueshift and linewidth broadening of the Mn²⁺ emission peak with increasing temperature. The average optical-phonon energy is approximately 50 meV. The activation energy reaches 79.32 meV, indicating that the introduction of Cu²⁺ in Mn-doped CsPb₂(BrCl)₅ NCs greatly enhances the energy transfer (ET) from the perovskite NC host to Mn²⁺, increasing the Mn²⁺ emission intensity. A clear understanding of the optical mechanism of Mn²⁺ emission is of great significance for the widespread application of codoped CsPb₂(BrCl)₅ NCs in optoelectronic devices.