Ni doping in CsPbCl₃ nanocrystals: the key to enhanced photoluminescence

This study presents a generic method to selectively enhance radiative pathways over non-radiative states by leveraging vibrational coupling between the host lattice and mid-gap states of doped transition metal ions. While previously demonstrated with Mn, this work successfully incorporates Ni²⁺ ions into CsPbCl₃ perovskite nanocrystals (NCs), showcasing the method's versatility and tunability for radiative decay rates. Structural analyses confirm Ni²⁺ integration, while temperature-dependent photoluminescence studies reveal that Ni-induced shallow trap states enable vibrational coupling, facilitating charge carrier back-transfer to excitonic states. At 2% doping, this mechanism optimally enhances radiative recombination, achieving room-temperature vibrationally assisted delayed fluorescence (VADF). Förster resonance energy transfer (FRET) experiments further validate the improved radiative efficiency. This work establishes transition metal doping as a transformative and selective strategy for tuning optical properties, paving the way for advancements in energy-efficient technologies such as light-emitting diodes, lasers, and photovoltaics.