We 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 tertbutyl-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 UVVis 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 (PC 61 BM) into the polymer chains. Polymer solar cells (PSCs) were fabricated by spin-coating a blend of each PT with the fullerene derivative (PC 61 BM) as a composite film-type photoactive layer; PBTtTPA/PC 61 BM-based PSCs showed superior photovoltaic (PV) performance to PTtTPA/ PC 61 BM-based PSCs in terms of conjugation and absorption band broadness. However, PBTtCz/ PC 61 BM-based PSCs showed inferior PV performance to PTtCz/PC 61 BM-based PSCs. The lower HOMO level led to a higher open-circuit voltage (V oc ; 0.74 V) and larger photo-energy conversion efficiency (h; 2.77%) of PTtCz/PC 61 BM-based PSCs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.