Photoconductivity of vinyl polymers

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Abstract
The photoconductivity of vinyl polymers: polyethylene (PE), polyvinyl fluoride (PVF), polyvinyl chloride (PVC), and polyvinyl bromide (PVBr) was investigated in different conditions of UV irradiation and electric field strengths. The degree of crystallinity was determined by x‐rays diffraction. The conductivity was investigated in air and in vacuum, by use of classical d.c. measuring set. Semitransparent, vacuum deposited Al electrodes were applied. The PE and PVF exhibit photoconductivity when irradiated with UV light of λ < 260 mμ. It was found that steady state photocurrents Ip were 10–100 times greater than dark currents Id and fulfilled the relation Ip ∼ Vn, where n > 1. The Ip value depends on the polarity of the illuminated electrode. The PVC films showed a slightly negative conductivity. Because of small stability of PVBr against the UV light, the results concerning photocurrents iu this case could not be interpreted. The kinetic studies of growth and decay of photocurrents showed that reaching steady state current depends upon the polarity of illuminated electrodes. The results were discussed in terms of electron mechanism of conductivity and SCLC theory. A tentative interpretation of the occurrence of steady state and of the possibility of the negative photoconductivity was given.

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