Functional Properties of Thin Films of Deoxyribonucleic Acid with Poly(3,4-ethylenedioxythiophene) and Poly(styrenesulfonate) Complex and Bistability of Their Photocurrent

Abstract

Functional photo- and electrical properties of thin films of DNA:PEDT-PSS were investigated. The sample currentvoltage
dependencies were linear and symmetrical down to liquid nitrogen temperature; the sample conductivity at
300 K was found to be 10–10 Ω–1cm–1. The thermal activation energy of the dark conductivity was about 33 meV
independently on the applied bias in the temperature region between 200 K and 300 K. Carrier trapping was evidenced
by the Thermally Stimulated Current method. Nevertheless this effect was weakly expressed, most probably because of
the fast recombination of generated carriers. Notably, a “bistable” photoconduction behaviour was identified below the
room temperature at constant light excitation. Upon illumination of the samples by ~500 nm – 800 nm light a marked
increase of the photocurrent took place by cooling them below 140 K – 160 K. In contrast, by heating the
photosensitivity remained increased up to 230 K – 240 K. This effect could be associated with the light-induced
modification of charge transport conditions in the samples.