Liquid 4,7-bis(1-decynl)-2,1,3-benzothiadiazole (DOBT) is found to exhibit good photoluminescence (PL) with high PL efficiency up to 17.8%. In particular, DOBT shows electron mobility of 5.2×10-6 cm2V-1s-1, demonstrating a promising n-type liquid semiconductor for optoelectronic application.