Band-offset reduction for effective hole carrier collection in bifacial silicon heterojunction solar cells

Abstract

Bifacial silicon heterojunction (SHJ) solar cells are gaining popularity owing to their potential for high performance. To achieve bifacial illumination, wide-gap hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) materials are used as front and rear surface fields, which significantly enhance the light absorbed into the cells. In this study, we reduced the band offset at the p/i interface of bifacial SHJ solar cells using an ultra-thin buffer layer of hydrogenated amorphous silicon oxide (a-SiOx:H) to increase the efficiency of hole carrier transport and collection. Effectively, we were able to enhance the open-circuit voltage (Voc) and fill factor (FF) by 0.97% and 9.59%, respectively. These results were confirmed through experimental procedures and simulations. Subsequently, the experimental efficiency with respect to the bifacial illumination of a rear emitter silicon heterojunction solar cell was increased by 23.6%, with a Voc of 729 mV, FF of 80%, and short-circuit current density of 40.5 mA/cm2.