Enhancing the thermal stability of polythiophene:fullerene solar cells by decreasing effective polymer regioregularity.

Kevin Sivula, Christine K Luscombe, Barry C Thompson, Jean M J Fréchet

Index: J. Am. Chem. Soc. 128 , 13988, (2006)

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Abstract

Regioregularity has been shown to be an important aspect for the properties of poly(3-hexylthiophene) both in the pristine material and in bulk heterojunction photovoltaics with the fullerene derivative PCBM. Here we present a straightforward method to adjust the effective regioregularity of poly(3-hexylthiophene) by introducing 3,4-dihexylthiophene into the polymer chain. By investigating bulk heterojunction morphology and photovoltaic performance upon annealing, we observe that polythiophene with 91% regioregularity maintains equivalent electronic properties but forms a more thermally stable interpenetrating network with PCBM than polythiophene with regioregularity >96%.