An amorphous mesophase generated by thermal annealing for high-performance organic photovoltaic devices

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.