SPECTROSCOPIC DETERMINATION OF TRAP DENSITY IN C-60-SENSITIZED PHOTOREFRACTIVE POLYMERS

A new and simple method for the determination of the trap density in C -60-sensitized photonfractive polymers is presented. We show that the radical anion of C-60 acts as the primary photorefractive hole trap, u sing the strong near-infrared absorption of C-60(-) to quantify the an ion concentration in situ. The spectroscopically determined concentrat ion correlates well with the photorefractive trap density obtained fro m analysis of the photorefractive performance. In our model, optical i rradiation is needed to activate the trapping sites, and the nonlinear optical chromophore acts as a temporary reservoir for the photogenera ted holes (compensator). This model is further clarified using cyclic voltammetry. (C) 1998 Elsevier Science B.V. All rights reserved.