Multifunctional process to improve surface passivation and carrier transport in industrial N-type silicon heterojunction solar cells by 0.7% absolute

Abstract

The commercial uptake of silicon solar cells with passivating contacts is set to accelerate over the next ten years, due to the potential for very high efficiency modules. Of particular interest are silicon heterojunction (SHJ) solar cells, which achieve high voltages by hydrogenated amorphous silicon (a-Si:H) passivation layers. A key challenge for the commercialization of SHJ solar cells is ensuring perfectly tuned a-Si:H and transparent conductive oxide (TCO) layers for optimal surface passivation and avoiding current-transport issues. Here, we demonstrate a new multifunctional post-cell fabrication process to address these challenges and improve both surface passivation and carrier transport in heterojunction solar cells. N-type silicon heterojunction solar cells with a 5-busbar metallisation scheme were fabricated in an industrial environment by CIE Power and subsequently received a high-throughput, multifunctional treatment at UNSW. This leads to significant improvements in the surface passivation, resulting in an increase in the open circuit voltage of 7 mV, from 730 mV to 737 mV, as well as improved carrier transport in the device, resulting in a significant reduction in series resistance from 0.79 Ω·cm2 to 0.37 Ω·cm2, and hence, an improvement in the fill factor of almost 2% absolute. This leads to an improvement in efficiency of 0.7 0.16% absolute, from 22.05% to 22.75%, with a peak efficiency of 22.93%.