Wang, H.-J.H.-J.WangTzeng, J.-Y.J.-Y.TzengChou, C.-W.C.-W.ChouHuang, C.-Y.C.-Y.HuangLee, R.-H.R.-H.LeeJeng, R.-J.R.-J.JengRU-JONG JENG2018-09-102018-09-102013http://www.scopus.com/inward/record.url?eid=2-s2.0-84872106496&partnerID=MN8TOARShttp://scholars.lib.ntu.edu.tw/handle/123456789/377447We synthesized a series of polythiophenes (PTs) featuring 2-ethylhexyl-substituted terthiophene (T) or quaterthiophene (BT) as the conjugated unit in the polymer backbone with pendant conjugated tert-butyl-substituted triphenylamine (tTPA)- or carbazole (tCz)-containing moieties as side chains, namely PTtTPA, PBTtTPA, PTtCz and PBTtCz. Incorporating T and BT moieties into the polymer backbone and attaching tTPA or tCz units promoted efficient conjugation within the extended conjugated frameworks of the polymers, resulting in lower band-gap energies and red-shifting of the maximal UV-Vis absorption wavelength. The higher electron-donating ability of tTPA resulted in broader absorption bands and lower band-gap energies of PTtTPA and PBTtTPA as compared with PTtCz and PBTtCz. Incorporation of the T and BT moieties into the polymer backbone enhanced the compatibility of PT and the fullerene derivative by reducing the side-chain density of PT, thus providing sufficient free volume for efficient incorporation of [6,6]phenyl-C 61-butyric acid methyl ester (PC61BM) into the polymer chains. Polymer solar cells (PSCs) were fabricated by spin-coating a blend of each PT with the fullerene derivative (PC61BM) as a composite film-type photoactive layer; PBTtTPA/PC61BM-based PSCs showed superior photovoltaic (PV) performance to PTtTPA/PC61BM-based PSCs in terms of conjugation and absorption band broadness. However, PBTtCz/PC 61BM-based PSCs showed inferior PV performance to PTtCz/PC 61BM-based PSCs. The lower HOMO level led to a higher open-circuit voltage (Voc; 0.74 V) and larger photo-energy conversion efficiency (η; 2.77%) of PTtCz/PC61BM-based PSCs. © 2013 The Royal Society of Chemistry.[SDGs]SDG7Composite films; Conversion efficiency; Energy gap; Fullerenes; Open circuit voltage; Photovoltaic cells; Polycyclic aromatic hydrocarbons; Polymers; Solar cells; Thiophene; Band gap energy; Conjugated units; Electron-donating ability; Fullerene derivative; Functionalized; Methyl esters; Photoactive layers; Photovoltaic; Polymer backbones; Polymer chains; Polymer Solar Cells; Polythiophene derivatives; PV performance; Quaterthiophene; Side-chains; Terthiophenes; Triphenyl amines; UV-vis absorptions; Conjugated polymersjournal article10.1039/c2py20477k