1 Polarization - dependent discharge in fibers of semiconducting ladder - type polymer

We report results on polarization-dependent photoinduced discharge in oriented fibers and films of ladder-type, electron-transporting polymer poly (ben-zimidazobenzophenanthroline), BBL. The photocarrier generation efficiency (φ) in the fiber which is indicated by the rate of discharge, is found to be distinctly higher for light polarized parallel to the fiber axis (P) as compared to the radially perpendicular direction (P ⊥). Similar results, with φ anisotropy ∼ 10 are obtained for oriented films. These observations are different from previously obtained results on polyparaphenylenevinylene (PPV). The results are compared with the polarization-dependent steady-state photoconductiv-ity measurements. We interpret these results on the basis of molecular and macroscopic features of the material.