Influence of high work function ITO:Zr films for the barrier height modification in a-Si:H/c-Si heterojunction solar cells

Abstract

We report the influence of magnetron sputtered zirconium-doped indium tin oxide (ITO:Zr) films with high mobility and work function on the heterojunction with intrinsic thin layer (HIT) solar cell. The addition of oxygen (O2) to argon (Ar) flow ratio during the deposition process improves the Hall mobility of the ITO:Zr films while the carrier concentration decreased. The small amount of oxygen resulted in an enhancement of work function while excess amount of O2 was not suitable for the electrical and surface properties of ITO:Zr films. The increase of O2/Ar flow ratio from 0% to 0.4% improved the work function from 5.03 to 5.13eV while the conductivity of ITO:Zr films remained about the same. The ITO:Zr films were employed as a front anti-reflection layer in a HIT solar cell and the best photo-voltage parameters were found to be Voc=710mV, Jsc=33.66mA/cm2, FF=72.4%, and η=17.31% for the O2/Ar flow ratio of 0.4%. The increase of ITO:Zr work function leads to an increase in open circuit voltage (Voc) and fill factor (FF) of the device. Therefore, the ITO:Zr films with high work function can be used to modify the front barrier height in the HIT solar cell.