Trapping mechanisms and dynamics in bis-triarylamine based photorefractive polymer composites

We report on the trapping mechanisms in bis-triarylamine (PATPD) based polymer composites. Although exceptional stability under continuous operation has been reported in PATPD-based composites, a small degradation of the response time in photorefractive devices under continuous operation has been found when improved styrene-based chromophores, with high figure-of-merit, are used. The accumulation of relatively large densities (∼10 ¹⁷ cm ^-3) of filled traps is observed even though to first approximation the transport manifold has the lowest ionization potential of all the moieties in the composite, so no apparent deep trapping sites are to be present. The results of spectroscopic studies where the formation of chromophore aggregates is explored and correlated with the formation of hole-trapping sites that dominate the temporal evolution of the photogenerated current density and C ₆₀ anion accumulation after several minutes of continuous operation will be presented and compared with numerical simulations considering a two-trapping site model in materials containing the chromophore DBDC.