2001 Fiscal Year Final Research Report Summary
Study on Excitons and biexcitons in Lead-Iodide-Based Perovskite-Type Low-Dimensional Crystals
| Project/Area Number |
12440081
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅰ(光物性・半導体・誘電体)
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KONDO Takeashi The University of Tokyo, Graduate School, School of Engineering, Associate Professor, 大学院・工学系研究科, 助教授 (60205557)
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| Co-Investigator(Kenkyū-buntansha) |
EMA Kazuhiro Sophia University, Faculty of Science and Technology, Professor, 理工学部, 教授 (40194021)
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| Project Period (FY) |
2000 – 2001
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| Keywords | Self-organized quantum well / Perovskite-type crystal / Lead halogenide / Low-dimensional material / Exciton / Biexciton / Nonlinear spectroscopy / Modulation spectroscopy |
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| Research Abstract |
1. Two-three-dimensional crystals
We have shown that lowest excitons in a "monolayer" two-dimensional crystal (C_6H_<13>NH_3)_2PblI_4 are nearly ideal two-dimensional Wannier excitons. The large binding energy of the lowest exciton is enhanced effectively by the so-called dielectric confinement effect. In addition, we have investigated excitons in a variety of 23-dimensional crystals, and have verified that the spatial and the dielectric confinements affects the Coulomb interlaction between electons and holes in the excitons. Moreover, we have successfully understood almost whole electronic structures in these crystals by group-theory analysis and first-principle band calculations. Based on this picture, we suggest three excitons (one allowed for E ⊥L c, one aloowed for E ‖ c, one forbiden (triplet)) exist and the triplet excitons affect,the relaxation process of the biexcitons.
2. One-dimensional crystals
We have measured optical spectra of the "corner-sharing" one-dimensional crystal [CH_3 CS(=NH_2)NH_2]_3 PbI_5, and have found lowest excitons with very strong one-dimensional characters. Based on the group-theory analysis, we have attributed all the structures (excitons) in the spectra including their polarization dependences. Excitons in this crystal are self-trapped ones and exhibit large Stokes shift. Exchange energy of the excitons have proved to be 70 meV which indicates the strong one-dimensionality of the system. Moreover, band calculations have shown that "sharing class" (corner-, line-, or face-sharing) and the lattice deformation strongly affect the bandgap energy of the lead-iodide-based one-dimensional crystals
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