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Formation of lotus surface structure for high efficiency silicon solar cell

고효율 실리콘 태양전지를 위한 lotus surface 구조의 형성

  • Jung, Hyun-Chul (Korea Institute of Ceramic Engineering and Technology) ;
  • Paek, Yeong-Kyeun (Department of Materials science and Engineering, Andong National University) ;
  • Kim, Hyo-Han (Korea Institute of Ceramic Engineering and Technology) ;
  • Eum, Jung-Hyun (Korea Institute of Ceramic Engineering and Technology) ;
  • Choi, Kyoon (Korea Institute of Ceramic Engineering and Technology) ;
  • Kim, Hyung-Tae (Korea Institute of Ceramic Engineering and Technology) ;
  • Chang, Hyo-Sik (Korea Institute of Ceramic Engineering and Technology)
  • 정현철 (한국세라믹기술원 이천분원) ;
  • 백용균 (국립안동대학교) ;
  • 김효한 (한국세라믹기술원 이천분원) ;
  • 음정현 (한국세라믹기술원 이천분원) ;
  • 최균 (한국세라믹기술원 이천분원) ;
  • 김형태 (한국세라믹기술원 이천분원) ;
  • 장효식 (한국세라믹기술원 이천분원)
  • Published : 2010.02.28

Abstract

The reduction of optical losses in mono-crystalline silicon solar cell by surface texturing is a critical step to improve the overall cell efficiency. In this study, we have changed the sub-micrometer structure on the micrometer pyramidal structure by 2-step texturing. The Ag particles were coated on the micrometer pyramid surface in $AgNO_3$ solution, and then the etching with hydrogen fluoride and hydrogen peroxide created even smaller nano-pyramids in these pyramids. As a result, we observed that the changes of size and thickness of nano structure on pyramidal surface were determined by $AgNO_3$ concentration and etching time. Using 2-step texturing, the surface of wafers is etched to resemble the rough surface of a lotus leaf. Lotus surface can reduce average reflectance from 10% to below 3%. This reflectance is less than conventional textured wafer including anti-reflection coating.

단결정 실리콘 태양전지의 광학적 손실을 감소시키는 표면 텍스쳐링은 최종 셀의 효율을 향상시키기 위하여 매우 중요하다. 본 연구에서는 2-step texturing의 공정으로 기존의 텍스쳐링에서 이루어진 피라미드에 수 많은 sub-micrometer 사이즈의 구조를 형성시켰다. $AgNO_3$ 용액으로 웨이퍼 표면에 Ag코팅을 한 후, 그 웨이퍼를 다시 HF/$H_2O_2$ 용액으로 수십초 동안 식각을 거치게 된다. 결과적으로, 피라미드 위에 생성된 수 nm사이즈의 구조물들은 $AgNO_3$의 농도 및 식각 시간의 변화에 의해 그 크기와 굵기가 변화하는 것을 알 수 있었다. 웨이퍼의 표면이 2-step texturing에 의해 식각이 이루어지면 연잎의 거친 표면과 비슷해지고, 그 결과 평균 10% 이상의 반사율을 보이던 기존 웨이퍼에서 3% 이하의 낮은 반사율을 얻을 수 있었다. 이는 일반적인 텍스쳐링과 anti-reflection coating을 거친 웨이퍼의 반사율보다 낮은 결과이다.

Keywords

References

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