Towards a manufacturable back-contact emitter-wrap-through silicon solar cell

The emitter-wrap-through (EWT) silicon solar cell is an all back-contact cell design that features a high efficiency while using solar-grade silicon materials. This paper reports on progress towards a low-cost manufacturable back-contact cell using the EWT design. We first show that the EWT cell is particularly well suited for thin (<200 μm) silicon solar cells. In particular, the EWT cell structure is inherently able to obtain high efficiencies (17% range) from low-quality materials by using thinner substrates and due to the double-sided carrier collection afforded by the n⁺pn⁺ structure. Secondly, we show that the manufacturing process is largely similar to conventional solar cells. Detailed estimates of manufacturing costs find that the EWT module could potentially reduce costs by one-half compared to current technology using front-contacted cells with screen-printed metallizations. Finally, we report on progress on several key processing steps required for a low-cost EWT cell design and process.