Effect of Zr doping power on the electrical, optical and structural properties of In–Zr–O anodes for P3HT : PCBM thin-film organic solar cells

Abstract

We investigated the effect of Zr doping power on the electrical, optical, structural and morphological properties of ZrO2 and In2O3 co-sputtered In–Zr–O (IZrO) thin films as transparent anodes for bulk-heterojunction organic solar cells (OSCs). Increased Zr doping power led to increased resistivity of as-deposited IZrO films while decreased resistivity of IZrO films annealed at 500 °C. Regardless of the Zr doping power, the IZrO film showed a high optical transmittance in the visible wavelength region and near infrared (NIR) wavelength region. The optimized IZrO film doped with 50 W ZrO2 radio frequency power showed a sheet resistance of 20.71 Ω/square and transmittance of 83.9%, which is comparable to the value of conventional In–Sn–O (ITO) films. The electronic structures measured by spectroscopic ellipsometry indicated expansion of unoccupied states near the conduction band with increased ZrO2 doping power. OSCs with transparent IZrO anodes exhibited similar performances to OSCs with reference ITO anodes due to the similar optical properties of IZrO and ITO films in the visible wavelength region. Due to their high transmittance in the NIR wavelength region, IZrO films are a promising replacement for ITO anodes in NIR absorbing OSCs.