Highly photoconductive poly(vinylcarbazole)/2,4,7-trinitro-9-fluorenone sol-gel material that follows a classical charge-generation model

Highly photoconductive properties are reported for organic-inorganic hybrid sol-gel thin film materials composed of a classical poly(vinylcarbazole)/2,4,7-trinitro-9-fluorenone (PVK/TNF) polymeric mixture, entrapped in a SiO2 matrix, whose pores have been chemically modified by organic functional groups. The highest photosensitivity obtained, 3.4 x 10(-10) cm Omega(-1) W-1 at E approximate to 22 V mu m(-1), at the optimum molar ratio between the active components, TNF, PVK, and SiO2, is in the range of the highest values ever reported for any PVK/TNF-based classical photoconductive material. It is demonstrated that the PVK/TNF-based sol-gel films follow Onsager's classical charge-generation model. The analysis of the photocurrent efficiency (Phi) of PVK/TNF-based sol-gel films by such a model provides the primary quantum yield of thermalized pair formation and the initial thermalized pair distance, phi(0) = 0.12 and r(0) = 66.1 angstrom, respectively, for the optimized sample. As a result of Onsager's analysis, a notorious improvement of the photocurrent generation process was achieved for low TNF concentrations.