A series of poly(dodecylthienylenevinylenes), C-12-PTVs-a: b, with tunable regioregularity and solubility have been synthesized using two isomeric comonomers with molar ratios from 0:10 to 5:5, and characterized by NMR spectroscopy, differential scanning calorimetry, absorption spectroscopy, cyclovoltammetry, and X-ray diffraction. For the first time, the aromatic and olefinic H-1 NMR peaks of regioregular head-tail C-n-PTVs are dearly assigned. No major difference in XRD peak intensity is observed among regiorandom and fully regioregular C-12-PTVs. V-oc of C-12-PTVs-a:b and PC60BM blend solar cells are in the range of 0.43 to 0.51 V and consistently decrease as regioregularity is reduced. C-12-PTV-3:7:PC60BM solar cells give the highest short-circuit current and practically same efficiency as that of C-12-PTV-1:9:PC60BM devices. The results suggest a new strategy to enhance processability of optoelectronic polymers without sacrificing their crystallinity and device performance.