Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (6): 1207-1214.doi: 10.3866/PKU.WHXB201504142

• PHYSICAL CHEMISTRY OF MATERIALS • Previous Articles    

Optimization of Intrinsic Silicon Passivation Layers in nc-Si:H/c-Si Silicon Heterojunction Solar Cells

QIAO Zhi1,2, XIE Xin-Jian1, XUE Jun-Ming3, LIU Hui1, LIANG Li-Min1, HAO Qiu-Yan1, LIU Cai-Chi1   

  1. 1 Engineering Laboratory of Photoelectric Functional Crystals in Hebei Province, Hebei University of Technology, Tianjin 300130, P. R. China;
    2 Institue of Applied Physics, Department of Mathematics and Physics, Shijiazhuang Tiedao University, Shijiazhuang 050043, P. R. China;
    3 China Hisun PV Technology Co., Ltd., Hengshui 053000, Hebei Province, P. R. China
  • Received:2015-01-05 Revised:2015-04-09 Published:2015-06-05
  • Contact: LIU Cai-Chi E-mail:ccliu@hebut.edu.cn
  • Supported by:

    The project was supported by the National High Technology Research and Development Program of China (863) (2012AA050301) and Scientific Research Program of Hebei Education Department, China (Z2010304).

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Abstract:

A series of intrinsic silicon thin films were prepared using radio- frequency plasma-enhanced chemical vapor deposition (RF-PECVD) at low temperature and low power density. We investigated the influence of silane concentration (CS) on the structural, optical, and electronic properties, and passivation quality of the intrinsic silicon films, and the performances of hydrogenated nanocrystalline silicon/crystalline silicon (nc-Si:H/ c-Si) silicon heterojunction (SHJ) solar cells. The results show that with decreasing silane concentration, substantial changes in the crystalline volume fraction, hydrogen concentration, structure factor, optical bandgap, and photosensitivity of the film take place in the transition zone. The passivation quality of intrinsic silicon thin films is decided by the hydrogen content and bonding structure of the film. Films close to the transition zone show good compactness and photosensitivities, high hydrogen content, and low state densities, and contain abundant SiH bonds. The films provide excellent passivation for c-Si surfaces and significantly enhance the open-circuit voltages of nc-Si:H/c-Si SHJ solar cells. However, the passivation quality deteriorates seriously when the film is too thin. In this work, the optimum silane concentration was found to be 6% (molar fraction). By optimizing the film thickness of the passivation layers with CS=6%, we obtained an nc-Si:H/c-Si SHJ solar cell with an open-circuit voltage of 672 mV, short-circuit current density of 35.1 mA·cm-2, fill factor of 0.73, and efficiency of 17.3%.

Key words: Intrinsic silicon thin film, Radio-frequency plasma enhanced chemical vapor deposition, Interface passivation, Minority carrier lifetime, Silicon heterojunction solar cell