Zirconium doped indium oxide thin films as transparent electrodes for photovoltaic applications

In this work we report on ultra-thin Zirconium doped In₂O₃ transparent conductive films grown at room temperature via RF-Magnetron co-sputtering. Samples from 15 nm to 90 nm thick, and low Zr atomic concentration (0.6-0.9 at., were annealed at T = 200° C after the deposition. The phase-transition from amorphous to crystalline, confirmed by XRD measurements, leads to an improvement of both electrical and optical properties. The thinnest film (15 nm) shows electrical resistivity as low as 5 x 10^-4 Ωcm, with carrier mobility of 20 cm²V^-1s^-1, and optical transmittance up to 80 infrared range. IZrO electrode performances were tested through external quantum efficiency (EQE) measurements on a semi-finite Silicon Heterojunction bifacial solar cell. The EQE values for 90 nm thick film are comparable to that of standard ITO when IZrO films are implemented as front electrodes. These results suggest that ultra-thin IZrO films may be successfully used to reduce costs and the amount of Indium used in Indium-based transparent conductive oxide layers for solar cells.