Combined Sensitisation of Benzaldehyde Diphenylhydrazones: Effect of Hydrazone Structure on Sensitization Efficiency
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Injection, spectral and combined (injection-spectral) sensitisations of several benzaldehyde diphenylhydrazones have been studied using the layers of amorphous selenium and complex compounds based on pyril dyes to broaden photosensitivity spectrum of electrophotographic carrier and to study sensitisation mechanism. Two photogeneration mechanisms for charge carriers have been shown to exist at a combined sensitisation, i.e. generation in the injection layer followed by the injection into a transport layer and generation in a transport layer on a dye. The excited dye molecules have been established to create hole strapping sites in a transport layer: it is exhibited in a different nature of photodischarge curves in selenium- and dye-absorbing regions at the negative surface potential. The effect of the substituent in a benzaldehyde fragment on the efficiency of injection, spectral and combined sensitisations of benzaldehyde diphenylhydrazones has been studied. The ionization potentials of hydrazones were determined by the two following methods: according to the charge transfer band of hydrazone-chloranil charge transfer complexes and by means of quantum-chemical calculations of hydrazone molecules to interpret the results obtained. In the course of quantum-chemical calculations the conjugation character was also determined in the molecules of benzaldehyde diphenylhydrazones.