Donor-acceptor-type polymers, PBDPBT-T, PBDPBT-TT, and PBDPBT-biT, were polymerized via Stille coupling reactions. In the unfavorable mode of DFT calculations, the distance between BDP in the two different polymer main chains showed different distance of repeating unit (Dn) according to the pi-spacers type. Especially, PBDPBT-TT caused larger D2 than PBDPBT-T and PBDPBT-biT. The UV-vis absorption spectra of PBDPBT-T and PBDPBT-biT films were red-shifted compared with the solution absorption, whereas that of a PBDPBT-TT film was blue-shifted. PBDPBT-T and PBDPBT-biT had high crystallinity and a tendency of face-on orientation. In contrast, PBDPBT-TT had low crystallinity. Owing to differences in packing formation, the polymers had different J(SC) values. When a polymer solar cell device was fabricated through a solution process, PBDPBT-biT (in a 1:1.5 ratio with PC70BM) exhibited a PCE of 4.50%, with a J(SC) value of 8.6 mA/cm(2), a V-OC value of 0.88 V, and an FF value of 59.4%. (C) 2016 Elsevier Ltd. All rights reserved.