Morphological modulation enabled by non-halogenated solvent-processed simple solid additives for high-efficiency organic solar cells

The simple-structural and volatile solid additive 1,4-dibromobenzene (DBrB) can outperform organic solar cells (OSCs) fabricated with 1,4-diiodobenzene and 1,4-dichlorobenzene in terms of power conversion efficiency (PCE). A remarkable PCE of 17.0% has been achieved in a binary OSC based on DBrB-optimized photoactive materials processed from non-halogenated solvents, which is mainly attributed to the formation of a three-dimensional interpenetrating network and the orderly arrangement of the photoactive materials by improving the intermolecular interaction. This optimized morphology enables efficient charge transfer/transport as well as suppressed charge recombination, resulting in the simultaneous increase in all photovoltaic parameters. More importantly, we demonstrate that non-halogenated solvent-processed DBrB enabled PM6:Y6-HU OSCs with an impressive PCE of 18.6%, which is the highest efficiency yet reported for binary OSCs. This study suggests that the novel DBrB volatile solid additive is an effective approach to optimizing the morphology and thereby improves the photovoltaic performance of OSCs.