Agressologie 1968 Mar-Apr;9(2):225-30.
The photoconductivity of melanin.

Potts A, Pin Chit A.

Biochim Biophys Acta 1978 Jan 3;538(1):164-70
A band model for melanin deducted from optical absorption and photoconductivity experiments.

Crippa PR, Cristofoletti V, Romeo N.

Natural and synthetic melanins have been studied by optical absorption and photoconductivity measurements in the range 200--700 nm. Both optical absorption and photoconductivity increase in the ultraviolet region, and a negative photoconductivity was observed with a maximum near 500 nm. This behaviour has been interpreted by the band model of amorphous materials and an "optical gap" of 3.4 eV has been determined.

J Photochem Photobiol B 2002:66(3):201-6
Photoconductivity of synthetic dopa-melanin polymer.

Jastrzebska M, Kocot A, Tajber L.
Department of Biophysics, Faculty of Pharmacy, Medical University of Silesia, Ostrogorska 30, 41-200, Sosnowiec, Poland

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.