Contact resistance of indium tin oxide and fluorine-doped indium oxide films grown by ultrasonic spray pyrolysis to diffusion layers in silicon solar cells

• A unique bifacial low-concentrator ITO/(p++nn++)Si/IFO solar cell was improved.
• ITO (or IFO)/n++-(or p++-)Si contact resistances were studied using a new method.
• The process for IFO deposition on n++-Si layers has been modified.
• ITO/(p++nn++)Si/IFO solar cell’s series resistance reduced from 0.39 to 0.26 Ω cm2.
• Solar cell extended its operating range of concentration ratios by a factor of 1.5.

A simple method is described for estimating the contact resistance between a transparent conducting oxide film and a diffusion layer in a silicon solar cell. We have investigated the effect of film growth temperature on the contact resistance between n++-Si and p++-Si layers and In2O3:Sn (ITO) and In2O3:F (IFO) films grown by ultrasonic spray pyrolysis. The effect of growth temperature on the properties of the SiOx layer in IFO/SiOx/n++-Si structures has been studied by Fourier transform infrared absorption spectroscopy. The process for IFO deposition on n++-Si layers has been modified in order to reduce the IFO/SiOx/n++-Si contact resistance. The use of modified IFO has reduced the series resistance of an ITO/(p++nn++)Cz-Si/IFO bifacial solar cell for low-concentration applications by 0.13 Ω cm2, from 0.39 to 0.26 Ω cm2; extended its operating range of concentration ratios by a factor of 1.5, from 1–3.5× to 1–5.3×; and improved its efficiency in the operating range from 17.6–17.9 to 17.7–18.2%.