Advances in opto-electronics require the development of 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 discovered 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 multi-dimensional coherent spectroscopy at cryogenic temperatures to reveal coherences involving triplet states of a CsPbI3 NC ensemble. Picosecond timescale dephasing times are measured for both triplet and inter-triplet coherences, from which we infer a unique exciton fine-structure level-ordering comprised of a dark state energetically positioned within the bright triplet manifold.
@article{arxiv.2002.08349,
title = {Partially-Bright Triplet Excitons in Perovskite Nanocrystals},
author = {Albert Liu and Diogo B. Almeida and Luiz G. Bonato and Gabriel Nagamine and Luiz F. Zagonel and Ana F. Nogueira and Lazaro A. Padilha and Steven T. Cundiff},
journal= {arXiv preprint arXiv:2002.08349},
year = {2020}
}