Morphological, optical, and electrical investigations of solution-processed reduced graphene oxide and its application to transparent electrodes in organic solar cells

Morphological, optical, and electrical properties of solution-processed reduced graphene oxide (r-GO) thin-films are investigated by varying on the number of spin-coating cycles and annealing temperature. Spin-coated r-GO thin-films all show full-covered morphologies with highly small rms roughness values ranging from ~1 to 2.5. nm. The sheet resistance of r-GO films can be controlled over two orders of magnitude by controlling both the spin-coating cycles and annealing temperature while conserving the transmittance values of 57-87%. The combination of coating cycles and heat-treatment temperature make the r-GO films as a useful transparent hole-extraction electrode for the application to organic photovoltaic cells.