Multidimensional coherent spectroscopy reveals triplet state coherences in cesium lead-halide perovskite nanocrystals

Advances in optoelectronics require materials with novel and engineered characteristics. A class of materials that has garnered tremendous interest is metal-halide perovskites, stimulated by meteoric increases in photovoltaic efficiencies of perovskite solar cells. In addition, recent advances have applied perovskite nanocrystals (NCs) in light-emitting devices. It was found recently that, for cesium lead-halide perovskite NCs, their unusually efficient light emission may be due to a unique excitonic fine structure composed of three bright triplet states that minimally interact with a proximal dark singlet state. To study this fine structure without isolating single NCs, we use multidimensional coherent spectroscopy at cryogenic temperatures to reveal coherences involving triplet states of a CsPbI3 NC ensemble. Picosecond time scale dephasing times are measured for both triplet and inter-triplet coherences, from which we infer a unique exciton fine structure level ordering composed of a dark state energetically positioned within the bright triplet manifold.

Automated summary

Advances in optoelectronics are driving the need for materials with novel characteristics, with metal-halide perovskites being a class of materials that has garnered significant interest. Recent research has focused on using perovskite nanocrystals in photovoltaic and light-emitting devices, revealing unique excitonic fine structures that contribute to efficient light emission. The study of cesium lead-halide perovskite nanocrystals through multidimensional coherent spectroscopy has provided insights into the fine structure level ordering of excitons within the bright triplet manifold.