Two new donor acceptor type of conjugated polymers derived from naphtho[1,2-c:5,6-c]bis(2-octyl[1,2,3]triazole) and dithieno[3,2-1E2',3'-d]silole were prepared by Stille polymerization. The thermal, electrochemical and photophysical properties of these copolymers were studied. Both polymers have excellent thermal stability with decomposition temperature up to 430 degrees C. The copolymers show medium band gap of 1.8 eV. Inverted bulk heterojunction solar cells in which these copolymers are used as electron donors in combination with PC61BM as the electron acceptor were fabricated. Under AM 1.5 G illumination at 100 mW/cm(2), device based on P1:PC61BM as the photoactive layer displays a moderate power conversion efficiency of 2.58% with an open-circuit voltage of 0.83 V, a short circuit current of 5.53 mA/cm(2), and a fill factor of 56.13%. Our work indicates that naphtho[1,2-c:5,6-clbis(2-octyl-[1,2,3] triazole) can be a promising electron-deficient building block for designing donor acceptor type of polymeric materials. (C) 2015 Elsevier Ltd. All rights reserved.