Two new donor-acceptor (D-A) copolymers containing dithienosilole (DTS) donor unit and benzotriazole (BTA) acceptor unit without and with thiophene bridge, PDTS-BTA and PDTS-DTBTA, were synthesized to study their structure-property relationships for the application in polymer solar cells (PSCs). Compared to PDTS-BTA, adding thiophene bridges in PDTS-DTBTA improves planarity and increases effective conjugation of the polymer main chain, which translated into broader and stronger absorption, higher hole mobility, and better photovoltaic performance. Under the illumination of AM1.5G, 100 mW/cm(2), the PSC based on PDTS-DTBTA/PC70BM demonstrated a power conversion efficiency of 3.80%, which is significantly improved in comparison with that (1.64%) of the device based on PDTS-BTA/PC70BM under the same experimental conditions.