Three Types Of Linear And Planar Structured Donor ( D ) -acceptor

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Three types of linear and planar-structured donor (D)–acceptor (A) type alternating copolymers were synthesized by incorporating intrachain noncovalent Coulomb interactions, based on 2,5-bisthieno[3,2-b]thiophene-1,4-bis(decyltetradecyloxy)benzene and benzothiadiazole (BT) moieties. The chain linearity and systematic adjustment of interchain organization was achieved by the incorporation of different number of electronegative fluorine atoms onto BT, which significantly affected the frontier energy levels, film morphology, and the resulting charge transport properties. Bimodal semi-crystalline orientation and charge carrier transport properties were studied by grazing incidence wide-angle X-ray scattering (GIWAXS) and polymer filed effect transistor (PFET) characteristics measurements. The hole mobility as high as 0.1 cm2/Vs in PFET was measured for poly(2,5-bisthieno[3,2-b]thiophene-1,4-bis(decyltetradecyloxy)benzene-alt-4,7-(5,6-difluoro-2,1,3 -benzothiadiazole)) (PPDTT2FBT), suggesting a strong self-organization in the linear configuration with conformation lock with the help of fluorine atoms. The linear and difluorinated PPDTT2FT also showed the highest power conversion efficiency (PCE, 6.4%) by blending with PC71BM, but showed a poorer photovoltaic performance compared to the wavy-structured counterpart, PPDT2FBT, reported previously. The mainly edge-on orientation of PPDTT2FT and poor blend film morphology attributed to the moderate PCE in the blends. Fine modulation
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