Modulating Acceptor Phase Leads to 19.59% Efficiency Organic Solar Cells.

Nonfullerene acceptors are critical in advancing the performance of organic solar cells. However, unfavorable morphology and low photon-to-electron conversion in the acceptor range continue to limit the photocurrent generation and overall device performance. Herein, benzoic anhydride, a low-cost polar molecule with excellent synergistic properties, is introduced in combination with the traditional additive 1-chloronaphthalene to optimize the aggregation of nonfullerene acceptors. This dual additive approach precisely modulates the morphology of various acceptors, significantly enhancing device performance. Notably, the method induces the formation of fine fibers with dense polymorph structures in BTP-base derivatives, achieving an optimal balance between exciton dissociation and charge collection in the active layers. As a result, the external quantum efficiency of the optimal devices is markedly improved in the wavelength range of 700-850 nm. Ultimately, power conversion efficiencies of 18.27% and 19.59% are achieved for devices comprising PM6:Y6 and PM6:L8-BO, respectively. The results reveal a convenient and effective method to control the morphology of nonfullerene acceptors and improve the photovoltaic performance of organic solar cells, paving the way for more efficient and practical organic photovoltaic technologies.