Additive-induced miscibility regulation and hierarchical morphology enable 17.5% binary organic solar cells

Due to barrierless free charge generation, low charge trapping, and high charge mobilities, the PM6:Y6 organic solar cell (OSC) achieves an excellent power conversion efficiency (PCE) of 15.7%. However, the deficient hole transfer from Y6 to PM6 limits the further enhancement of the device performance. Herein, we demonstrate an additive-induced miscibility and morphology control strategy to achieve the balance of exciton dissociation and charge collection, prompting an increase in the PCE of OSCs composed of PM6:Y6 from 15.7% to 17.5%, which stands as the top PCE value of PM6:Y6 binary OSCs. The external quantum efficiency (EQE) of the optimal device significantly improves in the wavelength range where Y6 harvests photons. Therefore, the short-circuit current density (JSC) was enhanced to 26.98 mA cm-2, achieving 94.4% of the maximum theoretical JSC obtained from the identical device configuration. The remarkable performance enhancement mainly results from the miscibility-driven donor and acceptor phase optimization with hierarchical morphology formation, leading to the improved photon-to-electron response of the Y6 phase, enhanced and balanced charge extraction and collection. Our findings highlight the significance of morphology control towards unleashing the full potential of OSC materials.