Non-Fullerene Acceptors with an Extended Pi-Conjugated Core: Third Components in Ternary Blends for High-Efficiency, Post Treatment-Free, Organic Solar Cells
Résumé
We report the synthesis of four non-fullerene acceptors (NFAs) with a "A-π-D-π-A" structure, in which the electron-donating core is extended. The molecules are differing by the nature of the solubilizing groups on the π-spacer and/or the presence of fluorine atoms on the peripheral electron-accepting units. The optoelectronic properties of the molecules are characterized in solution, in thin film and in photovoltaic devices. The nature of the solubilizing groups has a minor influence on the optoelectronic properties but affects the organization in the solid state. On the other hand, the fluorine atoms influence the optoelectronics properties and increase the photostability of the molecules in thin films. Compare to reference ITIC, the extended molecules show a wider absorption across the visible range and higher LUMO energy levels. The photovoltaic performances of the four NFAs were assessed in binary blends using PM6 (PBDB-T-2F) as the donating polymer and in ternary blends with ITIC-4F. Solar cells (active area 0.27 cm²) show power conversion efficiencies of up to 11.1% when ternary blends are processed from non-halogenated solvents, without any thermal posttreatment nor use of halogenated additives, making this process compatible with industrial requirements.
