Effective ink-jet printing of aqueous ink for Cu (In, Ga) Se2 thin film absorber for solar cell application

Chalcopyrite Cu (In, Ga) Se-2 (CIGSe(2)) thin film solar cells have emerged as a popular absorber material among thin film technologies, leading with photoconversion efficiency more than 22% on lab scale already being reported. Solution processed absorber ink using non-vacuum route found to be cost effective and for scalable approach of CIGSe(2) thin film solar cells. In this context, Inkjet printing emerges as a feasible technique for manufacturing CIGSe(2) thin film solar cells. Here, inkjet printing of aqueous precursor ink to successfully make high-quality CIGSe(2) absorber layer with controlled thickness and morphology is being presented. Precursor ink in aqueous medium and ink jetting parameters were optimized to obtain stable drop formation, essential for high-quality precursor film. The parameters that are found to strongly influence the formation of quality precursor CIG film were drop spacing and pretreatment temperature, discussed in detail. The effects of ink properties and printing parameters were investigated through rheological studies and optical microscopy; results suggested that uniform coverage of precursor CIG film can be achieved using a drop spacing of 175 mu m and pretreatment temperature of 150 degrees C. A single phase highly crystalline chalcopyrite CIGSe(2) thin film with dense morphology was obtained using atmospheric pressure selenization process. Semiconducting properties of film was studied by Mott-Schottky analysis. The photovoltaic performance of CIGSe(2) film solar cell device fabricated using non-vacuum inkjet route demonstrated 4.0% photoconversion efficiency on active device area of 4 x 4 mm(2).