Current Photovoltaic Research

Korea Photovoltaic Society (한국태양광발전학회)
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A Review on TOPCon Solar Cell Technology

  • Yousuf, Hasnain (Interdisciplinary Program in Photovoltaic System Engineering, Sungkyunkwan University) ;
  • Khokhar, Muhammad Quddamah (Department of Electrical and computer Engineering, Sungkyunkwan University) ;
  • Chowdhury, Sanchari (Department of Electrical and computer Engineering, Sungkyunkwan University) ;
  • Pham, Duy Phong (Department of Electrical and computer Engineering, Sungkyunkwan University) ;
  • Kim, Youngkuk (Department of Electrical and computer Engineering, Sungkyunkwan University) ;
  • Ju, Minkyu (Department of Electrical and computer Engineering, Sungkyunkwan University) ;
  • Cho, Younghyun (Department of Electrical and computer Engineering, Sungkyunkwan University) ;
  • Cho, Eun-Chel (Department of Electrical and computer Engineering, Sungkyunkwan University) ;
  • Yi, Junsin (Department of Electrical and computer Engineering, Sungkyunkwan University)
  • Received : 2021.06.15
  • Accepted : 2021.09.03
  • Published : 2021.09.30
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Abstract

The tunnel oxide passivated contact (TOPCon) structure got more consideration for development of high performance solar cells by the introduction of a tunnel oxide layer between the substrate and poly-Si is best for attaining interface passivation. The quality of passivation of the tunnel oxide layer clearly depends on the bond of SiO in the tunnel oxide layer, which is affected by the subsequent annealing and the tunnel oxide layer was formed in the suboxide region (SiO, Si2O, Si2O3) at the interface with the substrate. In the suboxide region, an oxygen-rich bond is formed as a result of subsequent annealing that also improves the quality of passivation. To control the surface morphology, annealing profile, and acceleration rate, an oxide tunnel junction structure with a passivation characteristic of 700 mV or more (Voc) on a p-type wafer could achieved. The quality of passivation of samples subjected to RTP annealing at temperatures above 900℃ declined rapidly. To improve the quality of passivation of the tunnel oxide layer, the physical properties and thermal stability of the thin layer must be considered. TOPCon silicon solar cell has a boron diffused front emitter, a tunnel-SiOx/n+-poly-Si/SiNx:H structure at the rear side, and screen-printed electrodes on both sides. The saturation currents Jo of this structure on polished surface is 1.3 fA/cm2 and for textured silicon surfaces is 3.7 fA/cm2 before printing the silver contacts. After printing the Ag contacts, the Jo of this structure increases to 50.7 fA/cm2 on textured silicon surfaces, which is still manageably less for metal contacts. This structure was applied to TOPCon solar cells, resulting in a median efficiency of 23.91%, and a highest efficiency of 24.58%, independently. The conversion efficiency of interdigitated back-contact solar cells has reached up to 26% by enhancing the optoelectrical properties for both-sides-contacted of the cells.

Keywords

Acknowledgement

This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (20203040010320) and (20183010014270).

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