Fullerene-based electron acceptors have provided the foundation for advances in fundamental understanding of charge photogeneration and practical developments in organic photovoltaics (OPVs) in the last 20 years. The use of fullerene derivatives such as [6,6]-phenyl-C<sub>70</sub>-butyric acid methyl ester (PC<sub>70</sub>BM) in combination with advances in the synthesis of narrow band gap polymer semiconductors have led to major progress in achieving power conversion efficiencies of up to11%. The prospects of enabling new pathways to more efficient OPVs while overcoming the small photovoltage, high cost, poor photochemical stability, and other limitations of fullerene-based OPVs have motivated efforts to discover alternative electron acceptor materials. Our recent efforts have led to the discovery of fullerene-free electron-accepting (n-type) polymers that result in all-polymer bulk heterojunction solar cells with efficiencies comparable to fullerene-based OPVs. We have also discovered small-molecule non-fullerene electron acceptors that enable highly efficient solar cells comparable to fullerene-based OPVs. In both cases higher photovoltages and increased charge photogeneration via photoinduced hole transfer were observed compared to fullerene systems. These recent advances suggest that molecular engineering of next generation non-fullerene organic photovoltaics are poised to move the field beyond the limitations of fullerene-based polymer solar cells.

High efficiency non-fullerene polymer solar cells

253rd National Meeting (2017)

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