Organic photovoltaic cells with vertically aligned crystalline molecular nanorods

We demonstrate the growth of vertically aligned nanorod arrays of copper phthalocyanine (CuPc) using the oblique angle deposition technique in high vacuum. High density nanorods with diameters down to 20 nm have been achieved with either stationary or rotational substrates. X-ray diffraction reveals the polycrystalline nature of the CuPc nanorods. Photovoltaic cells have been fabricated by spin-coating [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) onto the CuPc nanorod films to form the active region, and scanning electron micrographs show excellent infiltration of PCBM molecules into the gaps between the CuPc nanorods. A maximum power conversion efficiency of ηp = (1.8 ± 0.1)% under 1 sun AM 1.5G illumination has been achieved in a device with ∼40 nm long CuPc nanorods deposited on a 20 nm thick flat CuPc film, approximately twice of that of optimized bilayer CuPc/PCBM devices.