RF sputtered wide work function indium molybdenum oxide thin films for solar cell applications

Indium molybdenum oxide (IMO) thin films were deposited by RF magnetron sputtering on glass substrates at room temperature. The deposition and argon partial pressures were maintained at 6.0 x 10(-1) Pa and 3.0 x 10(-1) Pa, respectively. The oxygen partial pressure (OPP) was varied in the range 1.0-6.0 x 10(-3) Pa. The films were sputtered at 40 W for 30 min using the target consisted In2O3 (98 wt%): Mo (2 wt%). The films are polycrystalline with a slight preferential orientation along (222) plane. The crystallinity is increased with the increasing OPP. The negative sign of Hall coefficient confirmed the n-type conductivity. A maximum mobility similar to 19 cm(2) V-1 S-1 is obtained for the films deposited with OPP of 3.6 x 10(-3) Pa. The average visible transmittance calculated in the wavelength ranging 500-800 nm is ranging between 2% and 77%. The optical band gap calculated from the absorption data is varied between 3.69 and 3.91 eV. A striking feature is that the work function of the films is wide ranging 4.61-4.93 eV. A possibility of using the produced IMO films as transparent conducting oxide in photovoltaic applications such as organic solar cells is discussed in this article. (C) 2008 Elsevier Ltd. All rights reserved.