Volatile solid additives (SADs) are considered as a simple
yet
effective approach to tune the film morphology for high-performance
organic solar cells (OSCs). However, the structural effects of the
SADs on the photovoltaic performance are still elusive. Herein, two
volatilizable SADs were designed and synthesized. One is SAD1 with
twisted conformation, while the other one is planar SAD2 with the
S···O noncovalent intramolecular interactions (NIIs).
The theoretical and experimental results revealed that the planar
SAD2 with smaller space occupation can more easily insert between
the Y6 molecules, which is beneficial to form a tighter intermolecular
packing mode of Y6 after thermal treatment. As a result, the SAD2-treated
OSCs exhibited less recombination loss, more balanced charge mobility,
higher hole transfer rate, and more favorable morphology, resulting
in a record power conversion efficiency (PCE) of 18.85% (certified
PCE: 18.7%) for single-junction binary OSCs. The universality of this
study shed light on understanding the conformation effects of SADs
on photovoltaic performances of OSCs.