Theoretical Search of Nanostructure with Ground Bright Exciton States
Naval Research Laboratory, DC, Materials Science & Technology
Last year we published a letter in Nature entitled "Bright triplet excitons in cesium lead halide perovskites" [Nature 553, 189 (2018)]. This paper unravels the mystery behind the unusual brightness of fluorescent perovskite nanocrystals. Using both theory and experiment we discovered that the brightness arises from a unique property of these materials. Previously, the lowest energy exciton in all known semiconductors was a poorly fluorescent state known as the “dark exciton.” In perovskite nanocrystals we finally found a system where the lowest exciton is bright. The physical explanation of this phenomenon we presented can potentially lead to the exploitation of this effect in other materials. Bright-exciton semiconductors could then have a large impact on optoelectronic devices. We would like to search the fundamental physics, and strategies that to "break" the dark exciton influence. Building from our recent work, we wish to investigate several possible routes that should be pursued. Such a discussion can encourage researchers to engineer a new class of semiconductor nanostructures with bright excitons, leading to the development of biological emitters, super-radiant materials, and laser-gain media with unprecedented performance.