Combined Sensitisation of Benzaldehyde Diphenylhydrazones: Effect of Hydrazone Structure on Sensitization Efficiency

E.V Mikubayeva,N.S Kobotayeva,E.E Sirotkina

doi:10.18321/ectj602

E.V Mikubayeva, N.S Kobotayeva + Show 1 more

Open Access

https://doi.org/10.18321/ectj602

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Abstract

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<br />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<br />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<br />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<br />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.

Highlights

The problem of improving of photosensitivity of organic carriers based on organic semiconductors may be solved by applying the sensitisation of different types [1]
In case of the injection sensitisation the photosensitivity is observed only at the negative surface potential. In this case the photosensitivity spectrum corresponds to the spectrum of selenium absorption
The N1 substituent atom, the C2, C3, C5, C7, C8, and C10 benzaldehyde ring atoms, the C12, N14, and N15 hydrazone skeleton atoms, and the C16, C17, C21, C23, and C25 atoms of the phenyl ring lying in the molecular plane participate in conjugation in the H-2 molecule. It follows that H-2 is characterized by the longest conjugation chain and the lowest ionization potential, whereas hydrazone H-7 has the shortest conjugation chain and the highest ionization potential of all hydrazones studied in this work. This conclusion is in accordance with the experimental data obtained during the study of the sensitisation of benzaldehyde diphenylhydrazones, and the ratio between IP values in the series of hydrazones studied coincides with the data calculated by charge transfer complexes (CTC) absorption spectra

Summary

Introduction

The problem of improving of photosensitivity of organic carriers based on organic semiconductors may be solved by applying the sensitisation of different types [1]. We have obtained CTC of benzaldehyde diphenylhydrazones with chloranil and have determined hydrazones IP by electron absorption spectra of the complexes. In the absence of an injection selenium layer the spectrum of hydrazones photosensitivities sensitised by the complexes of pyrylium dyes corresponds to the absorption spectra of these dyes both at the positive and negative surface potentials.

Results

Conclusion