A novel alternating D-A copolymer, PPor-BT, with dioctylporphyrin (Por) as a donor unit and 5,6-bis(octyloxy)benzo-2,1,3-thiadiazole (BT) as an acceptor unit, was designed and synthesized by Pd-catalyzed Sonogashira-coupling reaction. The copolymer showed good solubility and film-forming ability. PPor-BT exhibited a broad absorption band from 350 to 950 nm with two peaks centered at 456 and 818 nm corresponding to the Soret band and Q-bands absorption of porphyrin segments, respectively. The employment of electron deficient BT unit to construct donor-acceptor structure observably broadened the absorption spectrum and enhanced the Q-band absorption of the porphyrin-based polymer. The HOMO and LUMO energy levels of the polymer are -5.06 eV and -3.63 eV, respectively. The solution-processed organic field-effect transistors (OFETs) were fabricated with bottom gate/top-contact geometry. The mobility of PPor-BT based OFEFs reached 4.3 x 10(-5) cm(2) V-1 s(-1) with an on/off current ratio of 10(4). This mobility is among the highest values for porphyrin-based polymers. (C) 2012 Elsevier Ltd. All rights reserved.