Poly N-vinylcarbazole PVK and Related Compounds

Melz (1972) measured photogeneration efficiencies of charge-transfer complexes fonned between PVK and 2,4,7-trinitro-9-fluorenone (TNF). The thermalization distance varied from 25 A for the 1.0 0.06 PVK TNF molar ratio to 35 A for the 1.0 1.0 molar ratio. For all concentrations, the primary quantum 

Okamoto et al. (1973,1973a, 1973b) measured photogeneration efficiencies of PVK. The results were explained by the field-assisted thermal dissociation of an exciplex formed between an excited carbazole group and an acceptor impurity. Okamoto et al. (1975) measured the efficiencies of /3-N-caibazolyl-ethyl vinyl ether, an oligomer of N-vinylcaibazole, and PVK. The efficiencies of the three compounds were comparable. The results were described by the dissociation of singlet excitons. 

Yokoyama et al. (1976, 1977) measured photo generation efficiencies of N-vinylcarbazole (VCZ) and VCZ-1-vinylnaphthalene copolymers. Both the photocurrent and the delayed fluorescence were enhanced in the copolymer. A quadratic dependence of the photocurient on light intensity was observed at high fields. From the photocurrent and emission spectra, it was concluded that photogeneration occurs via energy transfer from the caibazole (Cz) triplet state to the naphthalene (Nap) as 

the superscripts indicate the singlet and triplet states and the single and double asterisks the lowest and next higher excited states. The photogeneration thus involves the autoionization of a higher excited singlet state created by triplet-triplet annihilatioa 

Cherkasov et al. (1980) measured photogeneration efficiencies of PVK TNF charge-transfer complexes. The results show an increase in efficiency as the excitation time decreases. A similar phenomenon was later described by Gaidelis et al. (1984). The results were explained by an argument due to Boon (1972) and Akimov et al. (1980). According to the argument, the increase in efficiency is a result of an increase in the photoexcitation density and occurs in materials where the primaiy event consists of the formation of a bound electron- 

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