Absorption enhancement in thin-film solar cell using grating structure

Abstract

The enhancement of absorption in thin-film amorphous silicon solar cell based on guided mode resonance is theoretically investigated. This is achieved by patterning a grating with waveguide layer in the absorbing layer and an antireflective layer on the top. The optimized grating parameters are obtained by use of rigorous coupled-wave analysis and the simulated annealing algorithm in the visible region. The absorption at normal incidence is higher than 50% in the wavelength range 300-660 nm, and the peak absorption is higher than 95% for both TE and TM polarization. We studied the angle dependence of the integrated absorption spectrum in solar cell structures. The integrated absorption for TM polarization is larger than TE polarization in the angular range of 0-88o. In general, the averaged integrated absorption decreases as the incident angle increasing, but it is higher than 60% in the range 0-66o. So it is very weakly dependent on the angle of incidence. A physical understanding of enhanced absorption based on guided mode resonance effect is presented. It is found that the effect can effectively trap light in the absorber layer and enhance absorption in the active layer. Double-groove grating structure is also discussed for the sake of reducing reflection and enhancing absorption. The designed solar cells have high integrated absorption and are weakly dependent on incident angle, which should be of highly practical significance.