Transient Species Mediating Energy Transfer to Spin-Forbidden Mn d States in II–VI Semiconductor Quantum Dots

Abstract

The nature of the transient species leading to emission from the spin/orbital forbidden Mn d-d transition in doped semiconductor quantum dots has intrigued scientists for a long time. This understanding is important in the quest for energy efficiency as the energy from the conduction band is transferred efficiently to Mn in femtosecond timescale overcoming other non-radiative recombination pathways. In this work, we have shown the presence of the transient species using materials with band gaps in resonance with the energy of the Mn emission to understand the nature of the absorbing, transient and emitting species. Detailed studies lead to the emergence of transient Mn3+ state that is further corroborated with spin dependent density functional theory calculations. This opens up an unique opportunity to realize a reversible photo-chemical reaction and high radiative efficiency in a semiconductor nanostructure by controlling the spin state of the magnetic ion by external illumination.