Zhengxin Liu

Solar cells

 

Shanghai Institute of Microsystem & Information Technology Chinese Academy of Sciences (SIMIT),No. 235, Chengbei Rd., Jiading, Shanghai 201800, China

 

 

Email: z.x.liu@mail.sim.ac.cn

 

Biography

 

Abstract for Presentation

R&D towards industrialization of silicon heterojunction (SHJ) solar cells

 

 

Silicon heterojunction solar cell was invested by Sanyo in 1990s, it was named as HIT based on its fundamental structure: Heterojunction with Intrinsic Thin layer, and was adopted as a trademark HIT® by Sanyo [1]. The heterojunction structure of HIT solar cell has intrinsic and doped amorphous silicon (a-Si) layers on a randomly texturized mono crystalline silicon (c-Si) wafer, where, the intrinsic (i-) and p-type (p-) doped a-Si layers are deposited on one surface to obtain a p/n heterojunction, and the intrinsic and n-type (n-) doped a-Si layers are formed on the opposite surface to obtain a surface field structure. Transparent conductive oxide (TCO) layers and metal grid electrodes are formed on the doped a-Si layers. TCO layers have both functions of conduction for photo-generated carriers and anti-reflection for sunlight. The surface dangling bonds of c-Si wafer can be well passivated by the high-quality i-a-Si layers between the c-Si wafer and the doped a-Si layers, hence, a high open-circuit voltage (Voc) of more than 740 mV and high efficiency more than 26% can be obtained [2, 3].

The mass production of HIT solar cell was started around 2000s in Sanyo, nearly 1 GW production facilities were founded step by step in Japan, Malaysia and United States. Remarkable milestones have been achieved by Japanese companies, record efficiencies of 23.7% in 2011 and 24.7% were achieved by Sanyo and Panasonic in 2011 and in 2013 using 98-mm-thick Si thin wafers of a size over 100 cm2 [2, 3], which were about 2% absolutely higher than the conventional crystalline silicon solar cells. A record efficiency of 25.1% was reported by Kaneka in 2015 [4].

Research of silicon heterojunction solar cell became active in Europe and Asian countries from 2010s, it has been attracting more and more attentions due to its high energy conversion efficiency and simple batch production process, it is expected as the promising industrialization technology for the next generation. New names, such as SHJ, HJT etc. appeared to replace HIT to avoid trade disputes from the trademark HIT®. Several Chinese research groups and PV companies started R&D of SHJ solar cells around 2012. Recently, this trend was accelerated in China by Longi, Tongwei Soalr, Sunrise, Canadian Solar, and Huasheng, etc., these companies have setup polit production lines, the total production capacity has reached over 5 GW, the first GW manufacture factory will be founded by Tongwei in 2021. This paper will introduce the trends of industrialization an R&D of SHJ solar cell in China.

 

References

[1] M. Taguchi, et al., Proceedings of the Fifth Photovoltaic and Solar Energy Conference, PVSEC, 1990, pp. 689–692.

   [2] K. Yamamoto, et al., Proceedings of the 31st European Photovoltaic Solar Energy Conference and Exhibition,, 2015, pp. 1003–1005.

   [3] Wei Long, et al, Solar Energy Materials & Solar Cells 231 (2021) 111291