Synergistically optimizing the optoelectronic properties and morphology using a photo-active solid additive for high-performance binary organic photovoltaics

Additive engineering is one of the most effective strategies to manipulate the morphology and optoelectronic properties of bulk-heterojunction organic photovoltaics (OPVs). In this work, we explored a novel class of non-volatile photo-active additives with thermally activated delayed fluorescence (TADF) properties for high-performance OPVs. We found that energy levels play a key role in determining device performance. With a proper energetic structure and morphological features, a photo-active TADF-additive, i.e. 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN), could not only tune the morphology of the active layer, but also facilitate the diffusion and separation of excitons, as well as enhance charge transport properties. As a result, OPVs with 4CzIPN showed a better performance compared to those without 4CzIPN and achieved an impressive power conversion efficiency of 19.4%, which was one of the highest among binary OPVs. Thus, this work opens a new avenue of using TADF-based photo-active solid additives for high-performance OPVs. This work explores a new solid additive with TADF properties for high-performance OPVs. The TADF additive fine-tunes the morphology and enhances exciton diffusion and dissociation, resulting in an efficiency of 19.4%, making it one of the top binary OPVs.