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Study of Polarons and Solitons on Quasi-One-Dimensional, Mixed Valence Platinum Complexes

准一维混合价铂配合物极化子和孤子的研究

基本信息

批准号：
01460032
负责人：
KURITA Susumu
金额：
$ 4.93万
依托单位：
Yokohama National University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

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.

卤素桥连的混合价态铂配合物是典型的准一维半导体。基本吸收的特征在于Pt^<2+>到Pt^<4+>的价间电荷转移跃迁（CT带）。我们发现，当CT带被激光激发时，在带隙中间附近产生了两个新的吸收带。通过测量光致或卤素掺杂引起的ESR谱和光吸收谱，我们认为这些光致缺陷是单链上的电子和空穴极化子对。在卤素掺杂下，产生了单电荷极化子，并有利于通过P^+P^+ -> S^++S^+（或BP^<2+>）过程形成受限电荷孤子对（双极化子）.通过考虑电子-h距离的分布和极化子迁移率的温度依赖性，很好地解释了CT带低能侧发光峰随着E_X的减小而向低能移动，但在CT带以上保持不变的结果之一。室温下纯晶体和卤素掺杂晶体中的瞬态光电流测量结果表明，卤素掺杂不改变电子和空穴在E B方向（B ;链轴）的漂移迁移率以及E B方向上的电子漂移迁移率。然而，在碘化合物中，空穴在E B方向上的迁移率从2（纯的）变化到12 cm ^2/V·sec（掺杂的）。结果表明，极化子只有在高温下才能移动的，空穴极化子是通过卤素掺杂注入的，掺杂的卤素位于链间，是跳跃中心。