3D surfactant-dispersed graphenes as cathode interfacial materials for organic solar cells

Graphene dispersions in low-boiling-point green solvents have wide applications in coatings, conducting inks, batteries, electronics and solar cells. Two three-dimensional (3D) cathode interfacial materials (CIMs) (1,3,5,7,9,11,13,15-octa-(9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-vinylpentacyclo-octasiloxane) (POSSFN) and (1,3,5,7-tetra-(9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-adamantane) (ADMAFN) are excellent surfactants for dispersing graphene in ethanol at the concentration of 0.97–1.18 mg mL−1, in agreement with their calculated large adsorption energies on graphene. The results of electron spin resonance, Raman, scanning Kelvin probe microscopy and X-ray photoelectron spectroscopy measurements indicate that the amino groups could n-dope graphene or form dipole interaction with graphene. The two 3D-surfactant-based graphene composites (POSSFN-G and ADMAFN-G) can work as high-performance CIMs in organic solar cells (OSCs), which improve the power conversion efficiency (PCE) of the OSCs based on PM6:Y6 to 15.9%–16.1%. ADMAFN forms dipole interaction with graphene in ADMAFN-G and the composite CIM delivers high PCE of 16.11% in the OSCs, while POSSFN forms n-doped composition with graphene in POSSFN-G which works well as thicker CIM film in the OSCs.