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A donor-acceptor (D-A) conjugated copolymer PSBT-FTT , incorporating alkylthiophenylthienyl ( SBT ) side chains on benzo[1,2- b :4,5- b ']dithiophene units (BDT), was designed and synthesized. Compared to the analogical polymer PSB-FTT with alkylthiophenyl ( SB ) side chains, PSBT-FTT exhibits stronger interchain π-π interaction, more redshifted absorption spectrum, stronger absorption coefficient, better compatibility with (7,7)-phenyl-C 71 -butyric acid methyl ester (PC 71 BM), more effective exciton dissociation and higher hole mobility. Therefore, the PSBT-FTT -based bulk heterojunction polymer solar cells (PSCs) achieved a PCE value of 7.06% that is almost 50% higher than 4.83% of the PSB-FTT based PSCs. The result indicates that the introducing SBT side chains is an excellent strategy for designing high performance photovoltaic polymers. [ABSTRACT FROM AUTHOR]

A trilobal non-fullerene electron acceptor, BTT-3PDI , incorporating benzo[1,2- b :3,4- b ′:5,6- b ″]trithiophene (BTT) as the core and three bay-substituted perylenediimides (PDIs) as the arms, was designed and synthetized. It shows a high electron mobility of 3.69 × 10 −3 cm 2 V −1 s −1 because it is a crystalline semiconductor for the partially conjugated structure between PDI units and BTT core. BTT-3PDI shows a matched energy levels and a complementary absorption spectrum with PTB7-Th. The conventional polymer solar cells were fabricated without any processing additive or posttreatment. It showed a power conversion efficiency (PCE) of 1.35% because the unconspicuous microphase separation of the blend film leads to low electron mobility (1.67 × 10 −5 cm 2 V −1 s −1 ) and hole mobility (2.80 × 10 −5 cm 2 V −1 s −1 ). The study provides a proof that the crystalline PDI derivative with small dihedral angles between a core and PDI units can also avoid serious molecular aggregation and large phase separation in the active layer. [ABSTRACT FROM AUTHOR]

Two novel acceptor pended push–pull conjugated polymers PTT–DTBT and PT–DTTBT ，incorporating thieno[3,2– b ] thiophene in the backbone chain and conjugated side chains respectively, were designed and synthesized. The effects of the location of thieno[3,2– b ]thiophene units on the thermal, photophysical, electrochemical and photovoltaic properties of the polymers were investigated. Compared to the polymer PTT–DTBT , the polymer PT–DTTBT with thieno[3,2– b ]thiophene units in the side chains shows more broadened and red–shifted absorption, smaller band gap and higher hole mobility. Bulk heterojunction solar cells with the polymers as electron donors and (6,6)–phenyl–C 61 –butyric acidmethyl ester as the electron acceptor were fabricated, and the PT–DTTBT –based device exhibits a higher power conversion efficiency of 4.07% than that of the PTT–DTBT –based device (3.05%) without any processing additives or posttreatments. [ABSTRACT FROM AUTHOR]

Two conjugated polymers have been designed and synthesized by introducing benzothienoisoindigo as electron-withdrawing moieties on side chains. PBDTT-TBID based on alkylthienyl-substituted benzo[1,2- b :4,5- b ']dithiophene (BDT) derivative as electron-donating moieties possesses a low-lying highest occupied molecular orbital energy level of −5.38 eV, so its polymer solar cells (PSCs) shows a high open-circuit voltage (V oc) of 0.96 V, which is one of the highest V oc values among benzothienoisoindigo-based polymers. PBDT-TBID based on alkoxyl-substituted BDT derivative possesses better molecular coplanarity, stronger intramolecular charge transfer, stronger intermolecular π-π stacking, more suitable microphase separation with PC 71 BM, more effective exciton dissociation, and higher hole mobility than PBDTT-TBID , which lead to higher short-circuit current density (J sc = 11.81 mA cm−2), fill factor (FF = 0.58) and power conversion efficiency (PCE = 5.87%) values than those based on PBDTT-TBID. The PCE value is still higher than those of the reported benzothienoisoindigo-based polymers though it lags behind those of recent non-fullerene PSCs. Image 1 • Benzothienoisoindigo-based polymer achieves a V oc of 0.96 V. • PBDT-TBID shows the best photovoltaic performance in benzothienoisoindigo -based polymers. • The effects of the side chains on the properties of the polymers are studied. [ABSTRACT FROM AUTHOR]