Harnessing the Advantages of Dark Exciton in Perovskite Nanostructures as the Quantum Emitter and the Source of Charge Carriers

With support from the Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division, Professor Dong Hee Son at Texas A&M University will investigate the role of dark excitons in lead halide perovskite nanocrystals for generating light and charges with controlled quantum properties. Lead halide perovskite materials are recognized as efficient sources of light and charges for various applications such as photonics and solar cells. Professor Son's research team is studying lead halide perovskite materials at the few-nanometer size scale where a special excited state called the dark exciton becomes readily accessible. Dark excitons can have lifetimes a thousand-fold longer than the typical excited state in these materials. Additionally, dark excitons have the ability to generate light with properties that differ from those derived from the usual excited states. Professor Son's team is exploring effective ways of utilizing the dark excitons to produce light and charges with new properties that were previously unavailable, benefiting from the unique properties of the dark exciton. In addition to the scientific activities, this project will contribute to the training of graduate students in cutting edge experimental physical chemistry; this includes studies from groups underrepresented in the chemical sciences. Professor Son's team also plans to engage in outreach to K-12 students and to the local community through University-run public events. The Son research team is investigating the role of the dark exciton and its advantages in generating photons and charges with controllable quantum properties that cannot be readily obtained from the bright exciton. This project is focusing specifically on the energy and relaxation dynamics of single- and bi-exciton states formed from dark excitons, as well as the emissions of correlated photon pairs from dark excitons and spin-polarized states. These photon emission processes are enhanced by dark state longevity as well as new coupling pathways afforded by the dark excitons in lead halide perovskite nanocrystals. This research will leverage recent success by the Son group in accessing and probing the energetics and dynamics of the dark excitons separately from the bright excitons. This separate characterization of dark excitons is enabled by the confinement-enhanced bright-dark energy splitting in strongly quantum-confined perovskite nanocrystals. The research team combines the controllable magnetic doping and flexible ligand passivation in these nanocrystals, in conjunction with the high Q-factor microcavity, to provide enhanced interaction of light and nanocrystals, thereby exploring the advantages of the dark exciton in creating photons and charges with controllable characteristics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.