POLY(SILANE)-BASED HIGH-MOBILITY PHOTOREFRACTIVE POLYMERS

The photorefractive (PR) properties of guest-host polymer systems composed of the high-mobility charge-transporting host polymer poly(4-n-butoxyphenylethylsilane) (PBPES), a nonlinear dopant, and a sensitizer are characterized by four-wave mixing (FWM) and two-beam coupling (2BC). Steady-state diffraction efficiencies as high as 10(-4) (lambda = 753 nm, E0 = 16 V/mum; sample thickness, 175 mum) and rise times as short as 39 ms (lambda = 647 nm, E0 = 11.4 V/mum, 1-W/cm2 intensity) are observed by FWM; to our knowledge this is the fastest response observed in a PR polymer to date. In addition, net 2BC gain was observed in one material combination. The mobilities of PBPES and a mixture consisting of PBPES:Coumarin-153:C60 are measured, and the mobility of the latter is approximately 10(-4) CM2/(V s) at E0 = 10 V/mum, a factor of 10 larger than that of the undoped polymer. The rate of grating growth is analyzed within a charge-generation-limited model. The evidence indicates that carrier mobility is not the limiting factor in the PR response of these materials.