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(A) study on the growth of multiphase silicon-carbon film for si thin film solar cells 원문보기

  • 저자

    김선호

  • 학위수여기관

    Graduate School, Korea University

  • 학위구분

    국내박사

  • 학과

    新素材工學科

  • 지도교수

    金東煥

  • 발행년도

    2014

  • 총페이지

    xxi, 134장

  • 키워드

    Si thin film solar cell Contact barrier multiphase silicon-carbon Optical emission spectroscopy;

  • 언어

    eng

  • 원문 URL

    http://www.riss.kr/link?id=T13541921&outLink=K  

  • 초록

    Boron doped hydrogenated multiphase silicon-carbon (called as “multiphase silicon-carbon”) film with the properties of high electrical conductivity and low optical absorption coefficient has been grown by a plasma enhanced chemical vapour deposition (PECVD) method to apply to front contact layer in Si thin film solar cell. It consists of amorphous carbon (a-C:H), amorphous silicon (a-Si:H) and a crystalline silicon-like clustering phase (μc-Si:H). It has the advantage of reduces a low optical loss due to a wider band gap of a-C:H phase compared to amorphous silicon carbide (a-SiC:H) phase. The film can be fabricated in low RF power density and high hydrogen flow rate to increase the ratio of the a-C:H phase in amorphous matrix of film. The reaction between Si-based and C-based radicals is able to be suppressed by the deposition condition of low electron temperature (Te) in the plasma and the short residence time of source gases. This result is able to be achieved through the analysis of radicals in plasma, which is evaluated by optical emission spectroscopy (OES). It is used to define the plasma condition for growth of multiphase silicon-carbon film. The multiphase silicon-carbon film showed high electrical conductivity and a low optical absorption coefficient in the short wavelength region, as expected. It also was confirmed that the film is vertically conductive by conductive atomic force microscopy (C-AFM) analysis. In addition, it was verified that the μc-Si:H precipitates with a few nanometer size are uniformly distributed in the amorphous matrix through the transmission electron microscopy (TEM) observation. It can be predicted that the multiphase silicon-carbon film shows a superior property as the front contact layer in simulation result. The current density (Jsc) and external quantum efficiency (EQE) in short wavelength region rarely decreased in Si thin film solar cells with contact layer of multiphase silicon-carbon as the thickness of contact layer increase due to the low absorptance of it. Applying it for use as a front contact layer in a multi-junction Si thin film solar cell, it showed an improvement in the conversion efficiency due to the increase in the quantum efficiency in the short wavelength region. In addition, the fill factor enhanced without reduction of current density as increase of contact layer thickness. It was due to the low optical loss of multiphase silicon-carbon in short wavelength region. However, the hydrogenated silicon-carbon alloy film contained the a-SiC phase don't introduce the superior contact layer properties in Si thin film solar cell, although it has large carbon contents in film. It is understood that the electrical conductivity was deteriorated by large carbon contents, which is obstructed the crystallization of Si. These results showed that the multiphase silicon-carbon film is very effective to enhance the conversion efficiency when applied as the front contact layer in the thin film solar cell. In addition, it can be predicted that the performance of device, which is required the properties of high conductivity and low optical loss, improves by applying multiphase silicon-carbon film.


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