Nanocrystalline silicon-oxygen based tunneling recombination junctions in perovskite/silicon heterojunction tandem solar cells

Abstract

The tunneling recombination junction (TRJ) of efficient perovskite/silicon heterojunction tandem cells should possess excellent optoelectronic characteristics to minimize light parasitic absorption and carrier transport/recombination losses. One effective approach is the utilization of hydrogenated nanocrystalline silicon-oxygen (nc-SiOx: H) materials, which characteristics can be controlled by adjusting the flow rate of CO2 and doped gas during the fabrication process. By carefully screening the material properties, the suitable n/p-doped nc-SiOx: H materials can be identified. For n-nc-SiOx: H, it is necessary to use a lower CO2 flux and perform moderate doping, while for p-nc-SiOx: H, strict control of CO2 and Trimethylboron (TMB) fluxes at lower levels is essential to preserve the electrical properties. Compared to the TRJ based on nc-Si: H, the TRJ based on nc-SiOx: H exhibits notable improvements in the open-circuit voltage (VOC) and short-circuit current density (JSC) of the tandem cell. The VOC increases by 38 mV (from 1.822 V to 1.864 V), and the JSC gains 0.82 mA/cm2 (from 19.00 mA/cm2 to 19.82 mA/cm2). Consequently, the conversion efficiency of the tandem cell, with an aperture area of 0.5091 cm2, is enhanced from 25.70% to 27.16%. Additionally, by considering the distinct lateral and vertical growth characteristics of nc-SiOx: H, the fill factor (FF) experiences a significant enhancement when applied to the TRJ of large-area tandem cells. Specifically, the FF increases from 55.21% to 69.68%. As a result, for a tandem cell with an aperture area of 12.5 cm2, the conversion efficiency improves from 17.87% to 23.39%.