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

halogen - bridged,mixed-valence Platinum complexes are典型quasi-one-dimensional semiconductors. The fundamentalabsorption is characterized by the intervalence charge transfer transition from Pt^<2+> to Pt^<4+>CT band我们已经发现了两个新absorption bands grow up near the midgap when the CT band islaser. These photo-induced defects are concluded to be an electron and hole polarons pairon single chains by measuring the photo-induced or Halogen dope-induced ESR and optical absorptionspectra. 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 dueto the h recombination are studied in details as function of the excitation photon energy （e_x）和temperature. One of sults that the luminescence peak shifts to low energy with decreasing e_xat the low energy side of the CT band but is constant above the CT band良好的explained by taking account of the distribution of the e-h distance and the temperaturedependence of the mobility of polarons. Transient photocurrent measurements in pure andhalogen-doped crystals at room temperature show that the drift mobility of both electron and hole inthe 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 12cm ^2/V·sec (doped) in theiodine compound.这些results lead the conclusions that the polarons are mobile only athightemperature, hole polarons are injected by halogen dopingdoped halogens are located on the interchains and serve as hopping centers。

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.