| Outline of Annual Research Achievements |
This project accomplished two key goals: (1) controlled the photoluminescence blinking of quantum dots (CdSe-ZnS QDs) by the scavenging of deep holes generated in highly-excited QDs, which was by electron transfer beyond the limitations of Marcus Theory, and (2) generated and stablished multiple charge carriers in lead halide perovskite nanocrystals (PNCs), which was by the preparation of superlattices of PNCs. The above two results became possible by controlling the numbers of excitation photons, excitons generated and photoactivated nanocrystals. Blinking suppression in a QD and stabilization of charge carriers in PNC superlattices were accomplished by exceeding the conventional 1 photon: 1 exciton: 1 chromophore relation.
The above results were beyond the proposed goals, demonstrating (i) real-time blinking suppression in CdSe-ZnS QDs exposed to N,N-dimethylaniline (DMA), which was by electron transfer under a large positive Gibbs (free) energy change (ACS Nano 2018, 12, 9060) -beyond the expectations of Marcus theory. Furthermore, the blinking suppression was helpful for understanding and overcoming oxidation of PNCs (Angew. Chem. Int. Ed. 2019, 58, 4875). Also, this project accomplished optically-controlled amplified emission from PNC superlattices. Interestingly, under low-intensity excitation, a PNC superlattice showed unusually delayed emission (Angew. Chem. Int. Ed. 2017, 56, 1214), which became extremely fast and spatially confined at higher excitation intensities (ACS Energy Lett. 2018, 4, 133).
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