Solution-grown thin polystyrene films. I. DC electrical conduction

Abstract

The variation of electrical conduction with applied voltage and temperature has been studied in solution-grown pure and iodine-doped (PS) films 2500 AA thick. The study of the conductivity variation with the polymer thickness and with its temperature shows that only the Poole-Frenkel effect can explain the experimental results. Also, hysteresis and polarisation effects were observed in the I-V characteristics. The resistivity of the PS films was about 1015 Omega cm at room temperature and at a field of 105 V cm-1. An increase of about 102-103 orders of magnitude in conductivity was observed due to the doping of iodine in PS at room temperature. This is interpreted on the basis of the formation of charge transfer complexes in the film. The activation energy for conduction decreased from 0.79 to 0.67 eV at temperatures below Tg and from 1.0 to 0.89 eV above Tg on doping PS films with iodine (0.2 g of iodine per 100 ml PS solution).