Crystalline microwires of a phenyleneethynylene (PE) macrocycle self-assembled from solution exhibited superior photoconductive properties. Photoswitches fabricated with single wires afforded nA-scale photocurrents with on/off ratios of ca. 103. At a bias of 30 volts highest gain value achieved was up to 4.5. The stable and rapid responses to light qualify these microwire-based devices for excellent photoswitches or photodetectors.