Photoconductivity of synthetic dopa–melanin polymer

The photoconductivity effect in synthetic dopa–melanin polymer with relation to the charge hopping conduction has been investigated. Measurements of the rise and decay of photocurrents upon visible radiation (400–800 nm) and at temperatures of 293–326 K allowed the determination of the major trapping levels as follows: 56, 35 and 26 kJ/mol. Spectral response of the steady-state photocurrent in the range 367–1100 nm showed significant departures from the absorption spectrum of melanin. The high concentration of traps or recombination centers can explain the long time-constants calculated from the photocurrent rise and decay curves. The results obtained can support the postulated earlier polarons and hopping model of conductivity in synthetic dopa–melanin.