Can Singlet Fission Enhance the Performance of Organic Solar Cells?

The high efficiency of pentacene-fullerene (Pc-C$_{60}$) donor-acceptor solar cells has been ascribed to singlet fission, which generates two spin triplet excitons that each undergo ionization to give two pairs of electrons and holes [1,2]. For triplet ionization to give charge generation, the charge-transfer exciplex in the Pc-C$_{60}$ heterostructure should be energetically below the the molecular triplet state in Pc.Our initial calculations show that this is not a plausible scenario. We propose an alternate mechanism for the relatively high efficiencies of solar cells constructed from donors such as Pc, based on correlated-electron configuration interaction calculations [3] of ground state and photoinduced charge-transfer. \\[4pt] [1] Wilson M. W. B.; et al., J. Am. Chem. Soc, v133, 31, 11830-11833 (2011)\\[0pt] [2] Rao A.; et al., J. Am. Chem. Soc, v132, 36, 12698-12703 (2010)\\[0pt] [3] Yi Y.; Coropceanu V.; Br??das J. L.; J. Am. Chem. Soc, v131, 43, 15777-15783 (2009)