>24% Silicon Heterojunction Solar Cells on Meyer Burger’s on Mass Production Tools and How Wafer Material Impacts Cell Parameters

Abstract

The PV market has grown strongly in the last year again. More and more solar cell manufacturers focus on high efficiency solar cells with low cost. The industry is moving towards PERC Technology and the cell efficiency has been improving progressively. As theworldwide major PV market, China required since 2017 via ‘Top Runner’ Program high performance cell/module for module powerup to 325W on 60 cells. To reach this high performance, the hydrogenated amorphous (a-Si:H) /crystalline silicon (c-Si) hetero-junction technology(HJT) and other n-type technologies were discussed as the next candidate for mass production high efficiency solar cells beyondPERC. Additionally, HJT provides extra advantages: it offers a well suited application to achieve efficiencies above 23% with process temperatures below 200° C. The whole process flow is simple and with less process steps compared to the standard solarcell process [1]. HJT solar cells have $>90$% module bifaciality and a low temperature coefficient (-0.2 %/K), which provides additional benefit to the LCOE and output power for PV systems. The technology is compatible with extremely thin wafers below $130 \mu \mathrm{m}$ for mass production conditions. The recent world record HJT cell with an efficiency of 26.33% on a 180cm$^{2}$ n-type solar cell has been reached by Kaneka Corporation. This promising technology has shown even more potential for future mass production. In this study, we investigate the stability of HJT in mass production to process variationsand incoming wafer quality. By comparing various measurements during the manufacturing of more than 500,000 solar cells, we find thatwafer quality plays big role for cell efficiency. We propose a metric related to the bulk lifetime and bulk resistivity of incoming wafers as a requirement for stable cell efficiency in mass production.