Spectroscopic determination of trap density in C60-sensitized
A. Grunnet-Jepsen, D. Wright, B. Smith, M. S. Bratcher, M. S.
DeClue, J. S. Siegel, and W. E. Moerner
A new and simple method for the determination of the trap density
in C60-sensitized photorefractive polymers is presented. We show
that the radical anion of C60 acts as the primary photorefractive
hole trap, using the strong near-infrared absorption of C60-
to quantify the anion concentration in situ. The spectroscopically
determined concentration correlates well with the photorefractive
trap density obtained from analysis of the photorefractive performance.
In our model, optical irradiation is needed to activate the trapping
sites, and the nonlinear optical chromophore acts as a temporary
reservoir for the photogenerated holes (compensator). This model
is further clarified using cyclic voltammetry.