1990 Fiscal Year Final Research Report Summary
Study of Polarons and Solitons on Quasi-One-Dimensional, Mixed Valence Platinum Complexes
| Project/Area Number |
01460032
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | Yokohama National University |
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Principal Investigator |
KURITA Susumu Yokohama National University, Faculty of Engineering, Professor, 工学部, 教授 (30089833)
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| Co-Investigator(Kenkyū-buntansha) |
YAGI Mikio Yokohama National University, Faculty of Ebgineering, Associate Professor, 工学部, 助教授 (00107369)
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| Project Period (FY) |
1989 – 1990
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| Keywords | Polaron / Soliton / One-dimensional material / Photo-induced absorption / Photo-induced defect / Platinum complex |
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| Research Abstract |
Halogen-bridged, mixed-valence Platinum complexes are typical quasi-one-dimensional semiconductors. The fundamental absorption is characterized by the intervalence charge transfer transition from Pt^<2+> to Pt^<4+> (CT band). We have found that two new absorption bands grow up near the midgap when the CT band is excited by laser. These photo-induced defects are concluded to be an electron and hole polarons pair on single chains by measuring the photo-induced or Halogen dope-induced ESR and optical absorption spectra. Upon halogen doping, singly charged polarons are produced and the formations of confined charged soliton pairs (bipolarons) via the process P^++P^+ -> S^++S^+ (or BP^<2+>) is favored.
The luminescence spectra due to the e-h recombination are studied in details as function of the excitation photon energy (E_X) and temperature. One of results that the luminescence peak shifts to low energy with decreasing E_X at the low energy side of the CT band but is constant above the CT band, is well explained by taking account of the distribution of the e-h distance and the temperature dependence of the mobility of polarons. Transient photocurrent measurements in pure and halogen-doped crystals at room temperature show that the drift mobility of both electron and hole in the E b direction (b ; chain axis) and that of the electron in the E b do not change by halogen-doping. However, the mobility of hole in the E b direction varies from 2 (pure) to 12 cm^2/V・sec (doped) in the iodine compound. These results lead the conclusions that the polarons are mobile only athigh temperature, hole polarons are injected by halogen doping, the doped halogens are located on the interchains and serve as hopping centers.
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