Chemical Design Rules for Non-Fullerene Acceptors in Organic Solar Cells

Efficiencies of organic solar cells have practically doubled since the development of non-fullerene acceptors (NFAs). However, generic chemical design rules for donor-NFA combinations are still needed. Such rules are proposed by analyzing inhomogeneous electrostatic fields at the donor-acceptor interface. It is shown that an acceptor-donor-acceptor molecular architecture, and molecular alignment parallel to the interface, results in energy level bending that destabilizes the charge transfer state, thus promoting its dissociation into free charges. By analyzing a series of PCE10:NFA solar cells, with NFAs including Y6, IEICO, and ITIC, as well as their halogenated derivatives, it is suggested that the molecular quadrupole moment of approximate to 75 Debye angstrom balances the losses in the open circuit voltage and gains in charge generation efficiency.

Automated summary

Efficiencies of organic solar cells have been greatly improved by the development of non-fullerene acceptors (NFAs) and by analyzing the inhomogeneous electrostatic fields at the donor-acceptor interface. It is suggested that a molecular quadrupole moment of around 75 Debye angstrom can balance the trade-offs between open circuit voltage losses and gains in charge generation efficiency in PCE10:NFA solar cells.