Current Photovoltaic Research

Korea Photovoltaic Society (한국태양광발전학회)
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Improved Carrier Tunneling and Recombination in Tandem Solar Cell with p-type Nanocrystalline Si Intermediate Layer

  • Park, Jinjoo (Major of energy and appllied chemistry, Division of Energy & Optical Technology Convergence, Cheongju University) ;
  • Kim, Sangho (Department of Energy Science, Sungkyunkwan University) ;
  • Phong, Pham duy (College of Information and Communication Engineering, Sungkyunkwan University) ;
  • Lee, Sunwha (College of Information and Communication Engineering, Sungkyunkwan University) ;
  • Yi, Junsin (College of Information and Communication Engineering, Sungkyunkwan University)
  • Received : 2020.02.23
  • Accepted : 2020.03.04
  • Published : 2020.03.31
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Abstract

The power conversion efficiency (PCE) of a two-terminal tandem solar cell depends upon the tunnel-recombination junction (TRJ) between the top and bottom sub-cells. An optimized TRJ in a tandem cell helps improve its open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and efficiency (PCE). One of the parameters that affect the TRJ is the buffer layer thickness. Therefore, we investigated various TRJs by varying the thickness of the buffer or intermediate layer (TRJ-buffer) in between the highly doped p-type and n-type layers of the TRJ. The TRJ-buffer layer was p-type nc-Si:H, with a doping of 0.06%, an activation energy (Ea) of 43 meV, an optical gap (Eg) of 2.04 eV, and its thickness was varied from 0 nm to 125 nm. The tandem solar cells we investigated were a combination of a heterojunction with intrinsic thin layer (HIT) bottom sub-cell and an a-Si:H (amorphous silicon) top sub-cell. The initial cell efficiency without the TRJ buffer was 7.65% while with an optimized buffer layer, its efficiency improved to 11.74%, i.e., an improvement in efficiency by a factor of 1.53.

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References

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