From Mechanism to Energy Applications: Vibrationally Assisted Delayed Fluorescence in Doped Lead Halide Perovskite Nanocrystals

Doped lead halide perovskite nanocrystals (LHP NCs) represent a promising materials platform for advanced energy conversion and light-emitting technologies. Incorporation of long-lived dopant states introduces metastable energy reservoirs that capture photogenerated carriers and recycles them into host excitons through phonon-mediated vibronic coupling, giving rise to vibrationally assisted delayed fluorescence (VADF). This mechanism suppresses nonradiative losses, enhances photoluminescence quantum yield, and enables tunable emission lifetimes governed by dopant identity and host–dopant coupling strength. Insights from transition-metal (Mn2+, Ni2+ and Fe2+), nontransition (Sn2+), and lanthanide (Yb3+) codoping elucidate how spin-forbidden states, lattice softness, and interdopant interactions collectively dictate exciton recycling efficiency. By coupling long-lived dopant levels with vibrational dynamics, VADF transforms dopant centers from passive traps into active radiative participants. These principles establish VADF-active LHP NCs as a versatile platform bridging nanoscale photophysics and macroscopic energy harvesting, offering new design pathways for high-efficiency optoelectronic, photovoltaic, and photon-management applications.