Effects of indium concentration on the properties of In-doped ZnO films: Applications to silicon wafer solar cells

• ZnO:In thin films were prepared by rf-magnetron sputtering.
• No significant changes were observed in the ZnO:In properties.
• In-doped ZnO shows superior electric properties compared with pure ZnO.
• Interesting photovoltaic effect observed in ITO/ZnO:In(n)/c-Si(p) heterostructure
• Good quality of p–n junction in the ZnO:In(n)/c-Si(p) solar cell

In the present paper, high-quality In-doped ZnO (ZnO:In) thin films have been prepared by rf-magnetron sputtering on glass and p-type monocrystalline silicon substrates from an aerogel nanopowder target material. The nanoparticles with the [In]/[Zn] ratio varying between 0.01 and 0.05 were synthesized by the sol–gel method and the structural properties have been analyzed. The effect of different dopant concentrations on the electrical, optical, structural and morphological properties of the films has been investigated. The obtained ZnO:In films at room temperature are polycrystalline with a hexagonal structure and a highly preferred orientation with the c-axis perpendicular to the substrate. Scanning electron microscopy and atomic force microscopy have been applied for a morphology characterization of the films' cross-section and surface. The results revealed a typical columnar structure and very smooth surface. Films with good optical transmittance, around 85%, within the visible wavelength region, and low resistivity in the range of 10− 3 Ω·cm and high mobility of 4 cm2/Vs, were produced at low substrate temperature. On the other hand, we have studied the position of the p–n junction involved in an Au/In2O3:SnO2/ZnO:In(n)/c-Si(p)/Al structure by electron beam induced current. Current density–voltage characterizations in the dark and under illumination were also performed. The cell exhibits an efficiency of 6%.