Photosensitization of ZnO single crystals by means of dyes

Photoconductivity in single crystalline ZnO sensitized by Eosine (p-type) and Rhodamine 6 G (n-type) has been measured in the temperature region 80–300 K. The dependence on wavelength of the exciting light shows in both cases a structure with three peaks. Measurements of the dependence on time tell that rise and decay times are strongly wavelength dependent, and indicate further that at least two processes are involved in the build up and decay of the photocurrent. The activation energies found confirm this. A model with two different kinds of surface traps, including both energy and electron transfer is proposed.