New benzothiadiazole derivatives end-functionalized with carbazole and a-carboline, 4,7-di(9H-carbazol-9-yl)benzo[c][1,2,5]thiadiazole (1) and 4-(9H-carbazol-9-yl)-7-(9H-pyrido[2,3-bindol-9-yl) benzo[c][1,2,5]thiadiazole (2) were synthesized and characterized as organic semiconductors for organic thin-film transistors (OTFTs). Thermal, optical, and electrochemical properties of the corresoponding compounds were characterized. Thin films of compound 1 exhibited p-channel characteristics with carrier mobility as high as 10⁻⁴ cm²/Vs and a current on/off ratio of 10⁵ for top-contact/bottom-gate OTFT devices.