Prospects and Design Rules for Singlet Fission-Enhanced Visibly Transparent Organic Solar Cells

The quantum mechanical mechanism of singlet fission (SF), in which a singlet exciton rapidly decays to form two low-energy triplet states, has previously been demonstrated as a route to external quantum efficiencies above 100% in organic solar cells (OSCs). Unfortunately, this gain in short-circuit current is offset by a reduction in open-circuit voltage to accommodate efficient triplet dissociation at low-lying charge transfer states. Here, we implement a simple numerical model to assess the potential net effect of SF on the power conversion efficiency (PCE) of OSCs. In particular, we consider the application of SF to semi-transparent OSCs, which are of interest for use in solar windows and necessarily operate at low voltages to allow for visible light transmission. Under the assumptions of our model, the maximum PCE of a conventional (non-transparent) OSC exceeds that of the SF cell by > 1%. The SF cell competes more favorably with semi-transparent OSCs, suggesting that SF is best suited for devices in which power output is primarily limited by current generation, such as tandem solar cells.