Ameliorated trap density and energetic disorder via a strengthened intermolecular interaction strategy to construct efficient non-halogenated organic solar cells

Abstract

In light of environmental considerations, non-halogenated solvent casting is of critical importance for the commercialization of organic solar cells (OSCs). However, the severe traps and energetic disorder induced by the uncontrollable aggregation and anisotropic packing distribution in photoactive layers treated with non-halogenated solvents significantly limit the photovoltaic performance. In this work, a strengthened intermolecular interaction (SII) strategy is proposed, in which a non-halogenated dibenzyl ether (DBE) additive is developed and incorporated into non-halogenated OSC devices. The functional oxygen atom in the DBE molecule, together with the planar and rigid configuration, can induce collaborative hydrogen-bond and pi-pi intermolecular interaction with acceptors to construct a polycrystalline structure and further trigger the pre-aggregation process in the liquid-solid transition period. Consequently, the SII treatment can induce enhanced crystallinity and more favorable molecular orientation simultaneously, which can ameliorate the detrimental energetic disorder and efficiently elevate the carrier generation rate and transport, in addition to the diminished trap densities. Thus, the efficiency of non-halogenated OSC is upgraded from 17.1% to 19.4% after SII treatment, marking one of the highest performances for non-halogenated OSC devices. More strikingly, the roll-off of photovoltaic performance under the thick-film condition is appreciably mitigated, with a champion efficiency of 17.4% being achieved when the thickness reaches 300 nm, representing the superiority of SII strategy in the construction of eco-friendly, efficient, and thickness-insensitive OSCs.