Heterojunction organic solar cells based on donor-π-acceptor small molecule layers with controlled interface morphology

Small molecules have a great potential in developing organic solar cells owing to their well-controlled structure and tunable electronic properties by functionalization. Here, we use a classical fluorescent dye with a D-π-A structure, 4-(dicyanomethylene)-2-methyl-6-(4-dimethyl-aminostyryl)-4H-pyran (DCM), as an efficient light absorption layer with sensitivity at wavelengths of 400–600 nm where the aromatic amine/C60 cells have low absorbance. Combined with a p-type transporting layer of selected aromatic amines, the much improved layer and interface morphology yield solar cell power conversion efficiency up to 1.68% under AM 1.5 and 100 mW cm−2 illumination. The morphology of active organic layers, their interface, and the influence on the cell performance have been systematically studied.