A process detects defects in a semiconductor device, particularly a solar cell or solar cell arrangement, having at least one pn junction in a semiconductor layer of a semiconductor material with an indirect band junction. A voltage is applied to the at least one pn junction to operate it in the transmitting direction; and the radiation behavior of the semiconductor layer generated by the applied voltage, at least for partial ranges of the semiconductor layer, is optically detected and automatically examined for essentially one-dimensional intensity changes in order to detect mechanical defects.