Regulating the Packing of Non-Fullerene Acceptors via Multiple Noncovalent Interactions for Enhancing the Performance of Organic Solar Cells

Abstract

Three noncovalently fused-ring electron acceptors (<b>FOC6-IC</b>, <b>FOC6-FIC</b>, and <b>FOC2C6-2FIC</b>) are synthesized. Single crystals of <b>FOC6-IC</b> and <b>FOC2C6-2FIC</b> are prepared, and structure analyses reveal that the molecular backbone can be planarized via the formation of the intramolecular noncovalent interactions. These acceptor molecules can be packed closely in the solid state via π-π stacking and static interactions between the central phenylene unit and the terminal group with a distance of 3.3-3.4 Å. Besides, multiple intermolecular noncovalent interactions can be observed in the single crystal structure of the fluorinated acceptor <b>FOC2C6-2FIC</b>, which help increase the crystallinity of acceptors and the charge mobility of the blends. Photovoltaic devices based on <b>FOC2C6-2FIC</b> give a power conversion efficiency of 12.36%, higher than 12.08% for <b>FOC6-FIC</b> and 10.80% for <b>FOC6-IC</b>.