Ribbons of an air-stable, n-type organic single-crystal semiconductor, F16CuPc, are used to study photoswitches and phototransistors. High-quality, reversibly switching, fast photoswitches together with strongly photodependent field-effect phototransistors (see figure) of F16CuPc are made. The high light sensitivity and large on/off ratio of the phototransistors realize a new way to detect light and magnify signals in a single organic device, indicating a future in low-cost, ultrahigh density, organic photoelectric integration.