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The sensitization in photoconductive poly-N-vinylcarbazole was studied systematically. The sensitizers were conveniently divided into two types, opticaland chemical. The optical sensitization occurs with a smaller content of a dye, which extends the photoconductivity spectrum to its absorption band. Effective optical (or dye) sensitizers are found to be themselves photoconductive and n-type cationic and to have a slow photoresponse. The chemical sensitization occurs through the formation of a charge transfer complex with a considerable amount of a Lewis acid. The simultaneous addition of optical and chemical sensitizers induces amplified or additive effects; an amplified effect is observed when a strong acid is employed as a chemical sensitizer. A sensitized system with a strong acid shows a very slow photoresponse and may have fairly deep traps which act as a cause of the memory effect.

A photoconductive polymer, poly[1, 3-diphenyl-5-(4-vinylphenyl)-2-pyrazoline], has been synthesized from polystyrene via polyvinyl-acetophenone and polyvinylbenzalacetophenone. Under carefully controlled preparative conditions, a high degree of substitution has been obtained without its being insoluble. The photoconductive behavior of the polymer has been measured using a sandwich-type cell. The current obeyed Ohm’s law, and the value of Ip/Idwas 34 or 147 depending on whether the illuminated electrode was positive or negative respectively.

The photoconductive properties of polyacenaphthylene and nitrated polyacenaphthylene have been studied using both the sandwichcell method and the relative-surface-potential method. The polyacenaphthylene shows little photoconductivity, while the nitrated polymer obtained by the partial nitration of polyacenaphthylene shows considerable photoconductivity. The photocurrent depends on the degree of nitration.