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Novel tandem passivated contact approach for high-efficiency industrial TOPCon solar cells
  • +14
  • Sheng Ma,
  • Baochen Liao,
  • Feiyang Qiao,
  • D.X. Du,
  • D. Ding,
  • Chao Gao,
  • L. He,
  • Zhengping Li,
  • Xinyuan Wu,
  • Shuai Zou,
  • Xiaodong Su,
  • Rui Tong,
  • R. J. Yeo,
  • Xiang Li,
  • Weimin Li,
  • X.Y. Kong,
  • Wenzhong Shen
Sheng Ma
Shanghai Jiao Tong University School of Physics and Astronomy
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Baochen Liao
Nantong University
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Feiyang Qiao
Shanghai Jiao Tong University School of Physics and Astronomy
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D.X. Du
Shanghai Jiao Tong University School of Physics and Astronomy
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D. Ding
Shanghai Jiao Tong University School of Physics and Astronomy
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Chao Gao
Shanghai Jiao Tong University School of Physics and Astronomy
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L. He
Shanghai Jiao Tong University School of Physics and Astronomy
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Zhengping Li
Shanghai Jiao Tong University School of Physics and Astronomy
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Xinyuan Wu
University of New South Wales School of Photovoltaic and Renewable Energy Engineering
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Shuai Zou
Soochow University
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Xiaodong Su
Soochow University
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Rui Tong
JA Solar Technology Co Ltd
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R. J. Yeo
Institute of Materials Research and Engineering
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Xiang Li
Jiangsu Leadmicro Nano-Equipment Technology Ltd
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Weimin Li
Jiangsu Leadmicro Nano-Equipment Technology Ltd
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X.Y. Kong
Shanghai Jiao Tong University School of Materials Science and Engineering
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Wenzhong Shen
Shanghai Jiao Tong University School of Physics and Astronomy

Corresponding Author:[email protected]

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Abstract

Passivating contact solar cells have gradually become the mainstream cell technology due to their excellent performance, and further improving the conversion efficiency has become a focus of subsequent research. Typically, achieving excellent field-effect passivation and low contact resistivity in doped polycrystalline silicon (poly-Si) solar cells requires heavy phosphorus doping. However, this approach can lead to a predicament where excessive phosphorus diffuses into the Si substrate during annealing, causing recombination losses. To address this challenge, a tandem passivation contact structure incorporating an intrinsic amorphous silicon (a-Si ( i)) film within the passivation layers is introduced to retard the diffusion of phosphorus into the Si substrate. Comprehensive characterizations of the tandem structure were carried out to delve into the underlying mechanisms of films with the integrated a-Si ( i) layer, including simulations, surface microscopy, active dopants profiling, crystallographic structure, chemical bonding, elemental distribution, and electrical properties. Simulations revealed that the inserted intrinsic layer effectively counteracts the clustering of phosphorus atoms, leading to a more even distribution during crystal growth. Furthermore, active dopant profiles indicate the potential of the introduced a-Si ( i) layer to tailor the in-diffused dopant profile. Microscopy investigations revealed the occurrence of blistering when the a-Si ( i) thickness exceeds 30 nm. Passivation and contact performances of TOPCon solar cells were assessed as the a-Si ( i) thickness was varied. Notably, optimal electrical properties were achieved with 20 nm a-Si ( i) thickness. At this thickness, the implied open-circuit voltage ( iV OC) of the hydrogenated lifetime sample was promoted to more than 736.6 mV on the polished wafer, corresponding to the lowest single-side saturation current density ( J 0) of 4.3 fA/cm 2. In addition, a low contact resistivity of 1.4 mΩ·cm 2 was achieved. Based on this tandem passivation contact structure, industrial-sized TOPCon solar cells were fabricated, giving an average efficiency of 23.83%, 0.25% higher than that of the baseline counterparts on the production line. The above results demonstrate the role of the a-Si ( i) film as a buffer layer, retarding the diffusion of phosphorus into the Si substrate and obtaining a better passivation effect. This enables us to further tailor the doping profile for high-efficiency solar cells. Our work thus highlights a promising strategy to improve the performance of TOPCon solar cells and showcases its potential for implementation in industrial manufacturing.