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Photocurrents in thin YBa2Cu3O6films were measured at 300 K and 77 K. It is demonstrated that the classical semiconductor theory holds for this kind of material. The photocurrent results are discussed and compared with luminescence and optical transmission measurements. A large energy shift (0.63 eV), to date not observed in other semiconductors, between the photocurrent and luminescence maxima was measured. An oxygen surplus in the bulk of the sample is assumed to be the reason. Furthermore, it is demonstrated that at the critical temperature (Tc=93 K) of superconductive YBa2Cu3O7a change in the dark conductance behavior of semiconducting YBa2Cu3O6takes place.