Narrow Line Width Ni-Cu-Sn Front Contact Metallization Patterns for Low-Cost High-Efficiency Crystalline Silicon Solar Cells using Nano-Imprint Lithography

An in-house-developed nanoimprint lithography system is designed and developed to demonstrate a commercially viable method for creating Ni-Cu-Sn-based narrow linewidth finger patterns capable of effectively reducing shadow loss in the front contact metallization on industrial silicon solar cells. Finite element analysis simulation studies estimate that an optimal force of 138 MPa is required to generate damage-free patterns during nanoimprinting process. The poly (methyl methacrylate) residual layer is removed using reactive ion etching, which enhances the adhesion strength of Ni-Cu-Sn metallization. A low ohmic contact layer at the Si/Ni interface develops after sintering at 420 degrees C and formation of NiSi layer is confirmed through X-ray photoelectron spectroscopy analysis as a function of Ar+ ion etching time. An average cell efficiency of 18.10% is achieved for silicon solar cells with micropatterned Ni/Cu/Sn-based narrow linewidth front contact grid design, which can exhibit approximate to 1% enhancement in cell efficiency compared to commercial Ag screen-printed solar cells. The Ni/Cu/Sn-based front contact metallization can improve the cell performance by approximate to 6% compared to the commercial Ag screen-printed metallization by reducing shadow loss and thereby indicating its suitability toward deploying for cost-effective industrial solar cell manufacturing.