Sulfone-Modified Perylene Acceptors with Improved Permittivity for Bilayer Organic Solar Cells Processed from Non-halogenated Solvents

Abstract

Organic photovoltaics show high promise as a technology for sustainable energy conversion. A prominent strategy to reduce the substantial energy loss of organic solar cells is to synthesize high-permittivity (high-ε) active layer materials. However, despite the increase in permittivity, many of the high-ε materials achieved only inferior efficiencies, which is generally explained with a worse bulk heterojunction morphology. In this work, we tackled this issue by preparing high-ε acceptors and incorporating them in a bilayer setup, which we optimized using the systematic Design of Experiment (DoE) approach. The prepared acceptors are based on a perylene-linker-perylene scaffold, to which we attached polar sulfone-containing side chains. The relative permittivity of these acceptors increased by over 50% compared to their alkylated analogues. Simultaneously, some of the acceptors have greatly improved solubilities in non-halogenated “green” solvents. Both improvements enabled us to build bilayer organic solar cells from o-xylene and THF with PTQ10 as the donor, while simultaneously increasing the efficiency to 5.51% with a high open-circuit voltage of 1.3 V. Our results show that using a bilayer setup can successfully prevent morphology-related efficiency losses when employing high-ε materials. Combining this approach with a systematic optimization method (DoE) can unlock the theoretical potential of permittivity modification in organic solar cell research.