A high-performance ReS2-based thin-film transistor and photodetector with high on/off-current ratio (10(4)), high mobility (7.6 cm(2) V-1 s(-1)), high photoresponsivity (2.5 x 10(7) A W-1), and fast temporal response (rising and decaying time of 670 ms and 5.6 s, respectively) through O-2 plasma treatment is reported.