Photoluminescence and recombination luminescence in amorphous molecular semiconductors doped with organic dyes

Photoconductivity, photoluminescence (PL), and thermally stimulated luminescence of photoconductive poly-N-epoxypropylcarbazole and poly-N-vinylcarbazole films and non-photoconductive polyvinylbutyral, polyvinyl alcohol, polystyrene, and polyethylene films doped with cationic, anionic, and neutral dyes are studied. It is found that the PL of cationic dyes in photoconductive polymer films is enhanced in comparison to nonphotoconductive ones. The PL enhancement correlates with an increase in photoconductivity, with the quenching effect of an external electric field on the PL intensity, and with an increase in the intensity of the recombination luminescence. It is assumed that this enhancement is related to the presence of predimer traps for holes in the vicinity of dye ions in the films of carbazolyl-containing polymers. A model describing the trap formation upon the photoexcitation of holes into predimer states is suggested.