Room-Temperature Indium-Free Ga:ZnO/Ag/Ga:ZnO Multilayer Electrode for Organic Solar Cell Applications

We reported on the characteristics of an indium-free Ga-doped ZnO (GZO)/Ag/GZO multilayer electrode for use in bulk heterojunction organic solar cells. By inserting a very thin Ag layer between two GZO layers, we can fabricate a GZO-based transparent electrode with a low sheet resistance of 6 /square and a high optical transmittance of 87% at room temperature without postannealing. The power conversion efficiency (2.84%) of the organic solar cell fabricated on the GZO/Ag/GZO multilayer using neutral poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is much higher than that of the organic solar cell fabricated on the GZO electrode (1.57%) annealed at 500 degrees C. Indium-free GZO/Ag/GZO multilayer electrodes are expected to substitute for expensive indium tin oxide (ITO) electrode and decrease the cost of organic solar cells or flexible organic solar cells due to their comparable electrical and optical properties to those of crystalline ITO electrodes.