Optoelectronic advancements necessitate materials with novel and engineered properties. Metal-halide perovskites have sparked tremendous interest owing to meteoric increases in the photovoltaic efficiencies of perovskite solar cells.
Furthermore, recent advances in metal-halide perovskites have resulted in using perovskite nanocrystals (NCs) in light-emitting devices. It was recently discovered that the unusually efficient light emission of cesium lead-halide perovskite NCs might be due to a unique excitonic fine structure composed of three bright triplet states that interact minimally with a proximal dark singlet state.
Researchers used multidimensional coherent spectroscopy at cryogenic temperatures to reveal coherences involving triplet states of a CsPbI3 NC ensemble to study this fine structure without isolating single metal-halide perovskites NCs. The researchers measure picosecond time scale dephasing times for triplet and inter-triplet coherences, from which they infer a unique exciton fine structure level ordering composed of a dark state energetically positioned within the bright triplet manifold.
Researchers have measured and characterized optical frequency triplet and terahertz frequency inter-triplet coherences. They also presented evidence of an exciton band edge whose emission is partially quenched by an intermediate dark state, which sheds light on the contentious nature of exciton ground states in various perovskite NC materials. Perovskite NCs, as a material in its infancy, show promise for applications in optoelectronic devices.
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