Three-dimensional nanobranched indium-tin-oxide anode for organic solar cells.

A nanostructured three-dimensional (3D) electrode using transparent conducting oxide (TCO) is an effective approach for increasing the efficiency of optoelectronic devices used in daily life. Tin-doped indium oxide (ITO) is a representative TCO with high conductivity and a high work function for anode applications. This paper reports the fabrication of a large-area ITO nanostructure with a branch shape using an electron beam evaporation process at temperatures as low as 80 °C, which was free of any carrier gas and catalyst. The large surface to volume ratio in the anode by the ITO nanobranches increases both the hole mobility by a 3D pathway and light absorbance by scattering, resulting in organic solar cells with a 12% increase in photocurrent and 20% photoconversion efficiency based on the bulk heterojunction of P3HT [region-regular poly(3-hexylthiophene)] and PCBM [phenyl-C61-butyric acid methyl ester].