Solubility, highly efficient polymer donors

Due to the successful use of PCBM as acceptor material in solar cells, various attempts have been made to link Ceo covalently to an oligothiophene backbone in order to prepare D-A-based materials for photovoltaic devices by tuning their electronic properties [45, 46, 200, 201]. The attachment of fullerene units prevented large-scale phase separation in thin films and, despite the inclusion of bulky fullerene units, the soluble polymers retained their high order in thin films. However, the efficiency of such devices has been limited by competition between photoinduced electron transfer and energy transfer which occurs from the donor component to the fullerene. 

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