Design of Highly Efficient Light-Trapping Structures for Thin-Film Crystalline Silicon Solar Cells

We present a design optimization of a highly efficient light-trapping structure to significantly increase the efficiency of thin-film crystalline silicon solar cells. The structure consists of an antireflection (AR) coating, a silicon active layer, and a back reflector that combines a diffractive reflection grating with a distributed Bragg reflector. We have demonstrated that with careful design optimization, the presented light-trapping structure can lead to a remarkable cell-efficiency enhancement for the cells with very thin silicon active layers (typically 2.0-10.0 mum) due to the significantly enhanced absorption in the wavelength range of 800-1100 nm. On the other hand, less enhancement has been predicted for much thicker cells (i.e.,>100 mum) due to the limited absorption increase in this wavelength range. According to our simulation, the overall cell efficiency can be doubled for a 2.0-mum-thick cell with light-trapping structure. It is found that the improvement is mainly contributed by the optimized AR coating and diffraction grating with the corresponding relative improvements of 36% and 54%, respectively. The simulation results show that the absolute cell efficiency of a 2.0-mum-thick cell with the optimal light-trapping structure can be as large as 12%.

[1]  J. Nelson.  The physics of solar cells , 2003 .

[2]  M.A. Green,et al.  High-efficiency silicon solar cells , 1984, IEEE Transactions on Electron Devices.

[3]  R. Morf,et al.  Submicrometer gratings for solar energy applications. , 1995, Applied optics.

[4]  H. Grubin.  The physics of semiconductor devices , 1979, IEEE Journal of Quantum Electronics.

[5]  Yoshihiro Hamakawa.  Background and Motivation for Thin-Film Solar-Cell Development , 2004 .

[6]  Jürgen H. Werner,et al.  Quantum efficiency analysis of thin-layer silicon solar cells with back surface fields and optical confinement , 1996 .

[7]  Craig M. Herzinger,et al.  Ellipsometric determination of optical constants for silicon and thermally grown silicon dioxide via a multi-sample, multi-wavelength, multi-angle investigation , 1998 .

[8]  Yasha Yi,et al.  Efficiency enhancement in Si solar cells by textured photonic crystal back reflector , 2006 .

[9]  Wei-Ping Huang,et al.  Space mapping technique for design optimization of antireflection coatings in photonic devices , 2003 .

[10]  J. P. Connolly,et al.  Advances in Bragg stack quantum well solar cells , 2005 .

[11]  Theodor Tamir,et al.  Modal transmission-line theory of multilayered grating structures , 1996 .

[12]  M. Green,et al.  Light trapping properties of pyramidally textured surfaces , 1987 .

[13]  Alfred Thelen,et al.  Design of optical interference coatings , 1989 .

[14]  Devdas M. Pai,et al.  Analysis of dielectric gratings of arbitrary profiles and thicknesses , 1991 .

[15]  V. M. Andreev,et al.  Radiation resistant AlGaAs/GaAs concentrator solar cells with internal Bragg reflector , 2001 .

[16]  M. Stutzmann,et al.  Periodic light coupler gratings in amorphous thin film solar cells , 2001 .

[17]  T. Gaylord,et al.  Rigorous coupled-wave analysis of planar-grating diffraction , 1981 .