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Abstract: Arylenevinylene based bis(arylhalide) monomers were synthesized as low band gap electron-accepting blocks, and were copolymerized with 9,9-dioctyl-2,7-fluorene or 9-(heptadecan-9′-yl)-2,7-carbazole diboronic esters as electron-donating blocks using Suzuki coupling polymerization. Four alternating copolymers were synthesized through the combination of two different bis(arylhalide)s and diboronic esters, and their optical, thermal and electrochemical properties were characterized. The intra-molecular charge transfer interaction between the electron donating and electron accepting blocks in the polymeric backbone induced a broad absorption from 300 to 650nm. The optical band gap energies of the polymers were measured from their absorption onsets to be 1.97–2.18eV depending on the polymer structure. Bulk heterojunction photovoltaic devices were fabricated using the synthesized polymers as the electron donors and 6,6-phenyl C71-butyric acid methyl ester (PC70BM) as the electron acceptor. One of these devices showed a high power conversion efficiency of 3.22%, with an open-circuit voltage of 0.74V, a short-circuit current of 10.60mA/cm2, and a fill factor of 0.41 under air mass (AM) 1.5 global (1.5G) illumination conditions (100mW/cm2). [Copyright &y& Elsevier]

A series of donor-rich semi-random copolymers with various benzodithiophene (donor unit)/fluorinated-thienothiophene (acceptor unit) ratios – D2A, D3A, D5A, D7A – were designed and synthesized for use in polymer solar cells (PSCs). The polymer D1A was also synthesized for comparison. The optical and electrochemical properties of these polymers vary with the number of donor units in their polymer backbones. The device containing the polymer D5A exhibits a best power conversion efficiency (PCE) of 5.52% when the active layer thickness is 340 nm, a value that is 80% of its maximum PCE, whereas the best PCE of the D1A-based device is reduced by 32% when the active layer thickness is 310 nm. A large area (6,270 mm 2 ) D5A-based device prepared with the slot die-coating method was found to exhibit a best PCE of 6.54%, which is significantly better than that of the equivalent D1A-based large area device (4.03%). [ABSTRACT FROM AUTHOR]