An Amorphous Mesophase Generated by Thermal Annealing for High-Performance Organic Photovoltaic Devices



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Thermal annealing of a p-i-n organic photovoltaic device containing a crystalline benzoporphyrin donor and solvated crystals of a silylmethylfullerene acceptor increases the device performance at a temperature where partial desolvation of the acceptor produces an amorphous mesophase. This suggests that the mesophase improves the hierarchical ordering of the materials, that is, the morphology of the n-layer and the interfacial contact and, hence, the carrier generation efficiency at the donor–acceptor interface.