A new conjugated copolymer, poly{4,8-bis(triisopropylsilylethynyl)benzo[1,2-b:4,5-b']dithiophene-alt-4,7- bis(5-thiophen-2-yl)-5,6-difluoro-2-(heptadecan-9-yl)-2H-benzo[d][1,2,3]triazole} (PTIPSBDT-DFDTBTz), is synthesized by Stille coupling polycondensation. The synthesized polymer has a band gap energy of 1.9 eV, and it absorbs light in the range 300-610 nm. The hole mobility of a solution-processed organic thin-film transistor fabricated using PTIPSBDT-DFDTBTz is <TEX>$3.8{\times}10^{-3}cm^2V^{-1}s^{-1}$</TEX>. Bulk heterojunction photovoltaic cells are fabricated, with a conventional device structure of ITO/PEDOT:PSS/polymer:<TEX>$PC_{71}BM$</TEX>/Ca/Al (<TEX>$PC_{71}BM$</TEX> = [6,6]-phenyl-<TEX>$C_{71}$</TEX>-butyric acid methyl ester); the device shows a power conversion efficiency (PCE) of 2.86% with an open-circuit voltage (<TEX>$V_{oc}$</TEX>) of 0.85 V, a short-circuit current density (<TEX>$J_{sc}$</TEX>) of 7.60 mA <TEX>$cm^{-2}$</TEX>, and a fill factor (FF) of 0.44. Inverted photovoltaic cells with the structure ITO/ethoxylated polyethlyenimine/ polymer:<TEX>$PC_{71}BM/MoO_3$</TEX>/Ag are also fabricated; the device exhibits a maximum PCE of 2.92%, with a <TEX>$V_{oc}$</TEX> of 0.89 V, a <TEX>$J_{sc}$</TEX> of 6.81 mA <TEX>$cm^{-2}$</TEX>, and an FF of 0.48.