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Frontiers in Energy

ISSN 2095-1701

ISSN 2095-1698(Online)

CN 11-6017/TK

Postal Subscription Code 80-972

2018 Impact Factor: 1.701

Front. Energy    2017, Vol. 11 Issue (1) : 78-84    https://doi.org/10.1007/s11708-016-0435-5
RESEARCH ARTICLE
High-quality industrial n-type silicon wafers with an efficiency of over 23% for Si heterojunction solar cells
Fanying MENG1(),Jinning LIU1,Leilei SHEN1,Jianhua SHI1,Anjun HAN1,Liping ZHANG1,Yucheng LIU1,Jian YU1,Junkai ZHANG2,Rui ZHOU2,Zhengxin LIU1
1. Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology (SIMIT), Shanghai 200050, China
2. Xi’an Longi Silicon Materials Corp., Xi’an 710100, China
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Abstract

n-type CZ-Si wafers featuring longer minority carrier lifetime and higher tolerance of certain metal contamination can offer one of the best Si-based solar cells. In this study, Si heterojuction (SHJ) solar cells which was fabricated with different wafers in the top, middle and tail positions of the ingot, exhibited a stable high efficiency of>22% in spite of the various profiles of the resistivity and lifetime, which demonstrated the high material utilization of n-type ingot. In addition, for effectively converting the sunlight into electrical power, the pyramid size, pyramid density and roughness of surface of the Cz-Si wafer were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). Furthermore, the dependence of SHJ solar cell open-circuit voltage on the surface topography was discussed, which indicated that the uniformity of surface pyramid helps to improve the open-circuit voltage and conversion efficiency. Moreover, the simulation revealed that the highest efficiency of the SHJ solar cell could be achieved by the wafer with a thickness of 100 µm. Fortunately, over 23% of the conversion efficiency of the SHJ solar cell with a wafer thickness of 100 µm was obtained based on the systematic optimization of cell fabrication process in the pilot production line. Evidently, the large availability of both n-type ingot and thinner wafer strongly supported the lower cost fabrication of high efficiency SHJ solar cell.

Keywords n-type Cz-Si      thinner wafer      surface texture      high efficiency      SHJ solar cell     
Corresponding Author(s): Fanying MENG   
Just Accepted Date: 12 October 2016   Online First Date: 07 November 2016    Issue Date: 16 November 2016
 Cite this article:   
Fanying MENG,Jinning LIU,Leilei SHEN, et al. High-quality industrial n-type silicon wafers with an efficiency of over 23% for Si heterojunction solar cells[J]. Front. Energy, 2017, 11(1): 78-84.
 URL:  
https://academic.hep.com.cn/fie/EN/10.1007/s11708-016-0435-5
https://academic.hep.com.cn/fie/EN/Y2017/V11/I1/78
Fig.1  SHJ solar cell structure in this paper
Fig.2  Dependence of SHJ solar cell parameters on Si ingot position (6.2 inch wafers)

(a)Normalized Voc; (b) normalized FF; (c) normalized Eff

Fig.3  Surface of Cz-Si wafer

(a) Bare Si wafer; (b) pyramid size of around 10 µm; (c) pyramid size of around 5 µm

Fig.4  Reflectance from wavelength of 300 to1200 nm for various Si wafer surfaces
Fig.5  Influence of pyramid surface on passivation layers of SHJ solar cell

(a)Top-pyramid rough; (b) bottom-pyramid rough; (c) top-pyramid smooth; (d) bottom-pyramid smooth

Fig.6  Dependence of Voc on pyramids on textured Si surface for SHJ solar cells (wafer thickness 100-180 ?m)
Fig.7  (a) (b)

Variation of SHJ solar cell parameters with wafer thickness from simulation and experiment

(a) Simulation data; (b) experiment data

Fig.8  Performance of SHJ solar cell and its bendable PV module

(a) Current-voltage curve of SHJ solar cell with 100 µm thick wafer (5inch size); (b) bendable photovoltaic module with 100 µm thick SHJ solar cell

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