Electronic Structure of Radical Anions and Cations of Polysilanes with Structural Defects

Abstract

The electronic structure of a charged polysilane molecule is studied. The transient absorption spectroscopy was carried out for radical cations and anions of aryl-substituted polysilane molecules with Si-based defects by means of the nanosecond pulse radiolysis technique. Radical cations and anions of polysilanes displayed near-UV and IR absorption maxima at ca. 3.2−3.4 and 0.5−1 eV, respectively. They are ascribed to interband and subband transitions of polaron states and/or charge resonance states (CR) between σ-conjugated segments. The transition energy of the bands was strongly affected by the defects, showing a remarkable blue shift in IR absorption. The energy of the IR absorption band was interpreted as the degree of electron−phonon coupling. The energy rapidly increased from ca. 0.5 eV with an increase in the defect density and saturated at ca. 0.85 eV for radical cations and 0.95 eV for radical anions. It indicated that excess electrons and holes relatively localized at the defect structures, whe...