Non‐Fullerene Acceptors with an Extended π‐Conjugated Core: Third Components in Ternary Blends for High‐Efficiency, Post‐Treatment‐Free Organic Solar Cells

• Published in: ChemSusChem 2021-09, Vol.14 (17), p.3502-3510
• Main Authors: Avalos‐Quiroz, Yatzil Alejandra, Bardagot, Olivier, Kervella, Yann, Aumaître, Cyril, Cabau, Lydia, Rivaton, Agnès, Margeat, Olivier, Videlot‐Ackermann, Christine, Vongsaysy, Uyxing, Ackermann, Jörg, Demadrille, Renaud
• Format: Article
• Language: English
• Subjects: Additives; bulk-heterojunction; Energy conversion efficiency; Energy levels; Fluorine; Fullerenes; Heat treatment; Humanities and Social Sciences; Molecular orbitals; non-fullerene acceptors; Optoelectronics; organic photovoltaics; organic solar cells; Photovoltaic cells; Polymer blends; Solar cells; ternary blend; Thin films
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202101005

The synthesis of four non‐fullerene acceptors (NFAs) with a “A–π–D–π–A” structure, in which the electron‐donating core is extended, was achieved. The molecules differed 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 were characterized in solution, in thin film, and in photovoltaic devices. The nature of the solubilizing groups had a minor influence on the optoelectronic properties but affected the organization in the solid state. On the other hand, the fluorine atoms influenced the optoelectronics properties and increased the photo‐stability of the molecules in thin films. Compared to reference ITIC, the extended molecules showed a wider absorption across the visible range and higher lowest unoccupied molecular orbital 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) showed power conversion efficiencies of up to 11.1 % when ternary blends were processed from non‐halogenated solvents, without any thermal post‐treatment or use of halogenated additives, making this process compatible with industrial requirements. The third component: Four non‐fullerene acceptors (NFAs) with an extended π‐conjugated core are synthesized and their optoelectronic properties are fully described. The fluorinated NFAs are soluble in non‐halogenated solvents and demonstrate a high photochemical stability. It is shown that they can be advantageously used as third components in ternary blends with PM6 and ITIC‐4F for the fabrication of high‐efficiency, post‐treatment‐free organic solar cells.