Palestrante: Prof. Dr. Jaime Frejlich Sochaczewsky (IFGW/DFMC/Laboratório de Óptica)

Abstract: We report on the use of Wavelength-Resolved Photoconductivity (WRP) to find out the energetic position of photoactive centers in the Band-Gap of photorefractive crystals. Although our present results are, for the moment, limited to these crystals, that are photorefractive (light may change their refractive index) and also photoconductive (light may excite electrons from photoactive centers into extended states), this technique is expected to be useful for photoconductive materials in general.

We briefly describe the technological interest of these crystals and the home-made instrument here used.

We will also show that a thin photorefractive crystal plate sandwiched between transparent ITO electrodes becomes a photoelectric device, based in the so-called “Dember” effect. Preliminary results show their efficiency to be much weaker than conventional semiconductor devices but the use of different sandwich thicknesses and photoconductive naterials (maybe polymers) may open new possibilities in this fiekd.