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 ca 75 Debye A balances the losses in the open circuit voltage and gains in charge generation efficiency.
@article{arxiv.2201.11626,
title = {Chemical design rules for non-fullerene acceptors in organic solar cells},
author = {A. Markina and K. -H. Lin and W. Liu and C. Poelking and Y. Firdaus and D. R. Villalva and J. I. Khan and S. H. K. Paleti and G. T. Harrison and J. Gorenflot and W. Zhang and S. De Wolf and I. McCulloch and T. D. Anthopoulos and D. Baran and F. Laquai and D. Andrienko},
journal= {arXiv preprint arXiv:2201.11626},
year = {2022}
}