Photocarrier generation and transport in<i>σ</i>-bonded polysilanes

Abstract

Polysilanes, even those containing no \ensuremath{\pi} electrons, are found to be excellent photoconductors. In the materials studied to date, only holes are mobile but they have a well-defined mobility of about ${10}^{\mathrm{\ensuremath{-}}4}$ ${\mathrm{cm}}^{2}$/V?at room temperature. In poly(phenylmethylsilane), the material we have studied most intensely, the hole-generation quantum efficiency is about 1% at high electric fields and the experimental results indicate that the holes are generated when excitons, formed when a photon is absorbed, diffuse to the surface of the film. The exciton diffusion length is found to be 500 A\r{}. These results help confirm the existence of extensive conjugation among \ensuremath{\sigma} bonds in polysilanes.