A Non-fullerene Acceptor with Enhanced Intermolecular π‑Core Interaction for High-Performance Organic Solar Cells

Understanding
the molecular structure and self-assembly of thia­diazole-derived
non-fullerene acceptors (NFAs) is very critical for elucidating the
origin of their extraordinary charge generation and transport properties
that enable high power conversion efficiencies to be achieved in these
systems. A comprehensive crystallographic study on a state-of-the-art
NFA, Y6, and its selenium analog, CH1007, has been conducted
which revealed that the face-to-face π-core
interaction induced by benzo­[2,1,3]­thia­diazole S–N-containing
moieties plays a significant role in governing the molecular geometries
and unique packing of Y6 and CH1007 to ensure their superior
charge-transport properties. Moreover, benefitting from the red-shifted
optical absorption via selenium substitution, photo­voltaic devices
based on a PM6:CH1007:PC71BM ternary blend
delivered an exceptionally high short-circuit current of 27.48 mA/cm2 and a power conversion efficiency of 17.08%.