High mobility transparent conductive W-doped In2O3 thin films prepared at low substrate temperature and its application to solar cells

W-doped In2O3 transparent conductive film was developed at a low substrate temperature of 200 °C by reactive plasma deposition technique for the applications to silicon heterojunction solar cell. The maximum Hall mobility of 89 cm2/V s with a corresponding carrier concentration of 1.6×1020 cm−3 was achieved at a relatively high oxygen partial pressure of 7.2×10−4 Torr without any special treatment. According to the Hall effect measurements at variable temperature from 80 K to 300 K, high Hall mobility was mainly attributed to the ionized impurity scattering, neutral impurity scattering and phonon scattering, grain boundary scattering only plays the minor role in the carrier transportation of IWO film in this work. Additionally, XRD results show the samples have a cubic phase of bixbyite-type In2O3 polycrystalline structure with a preferential orientation of (222) plane. The plasma wavelength of larger than 2.3 μm is very beneficial for sunlight transparency. Consequently, IWO is applied to a-Si/c-Si heterojunction solar cells, 20.8% of conversion efficiency has been obtained under the optimized experimental conditions.