Thieno[3,2-b]thiophene-bridged polymer semiconductor, P(BDT-TT-BO), featuring benzoxadiazole (BO) acceptor unit was designed and synthesized. P(BDT-TT-BO) showed broad absorption, in the wavelength range of 350-700 nm, and low highest occupied molecular orbital (HOMO) energy level (-5.31 eV). The benzoxadiazole-based polymer semiconductor exhibited very promising optoelectronic performance. Power conversion efficiency of the polymer solar cell with P(BDT-TT-BO) as donor reached 7.05%, which is the champion efficiency in benzoxadiazole containing conjugated polymers and comparable to that of the most efficient benzothiadiazole-based donor polymers. The sensitive dependence of carrier mobility on the annealing temperature of the polymer semiconductors was systematic studied. After annealing at 200 degrees C, P(BDT-TT-BO)-based polymer field effect transistor showed a mobility of more than 12 times that of unannealed devices, reached 0.023 cm(2) V-1 s(-1), with a high on/off current ratio of 2.7 x 10(5).