The effect of trap density on the space charge formation in polymeric photorefractive composites

The effect of trap density on the space charge formation of polymeric photorefractive (PR) composites was studied using the modified Schildkraut differential equation. The densities of electrons, holes, and traps, as well as the rates of generation, recombination, trapping, and detrapping are examined. The steady-state and temporal behaviors of photocurrent and space charge field (E(sc)) formation dependence on the trap density are also discussed. The charge transport dynamics influenced by the presence of the trap molecules controls the formation of E(sc) via charge trapping, charge detrapping, and charge recombination. Experimental studies of photocurrent and E(sc) in poly[methyl-3-(9-carbazolyl) propylsiloxane]-based polymeric PR composites were carried out to demonstrate the applicability of the model.This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MEST) (Grant No. R11-2007-050-01003-0) and by the research fund of HYU (Grant No. HYU-2008-T)