Improvement of solar cell efficiency using nano-scale top and bottom grating

Abstract

We study solar-cell designs using nano-grating on both top (transmission) and bottom (reflection) of the solar cell. First, we perform simulations based on rigorous coupled wave analysis (RCWA) to evaluate the diffraction top gratins. In RCWA method, we calculate up to 20 harmonics, and sweep the launch angle of incident light from 0 to 90 degree. The incident light varies from100nm to 1200nm wavelength. Triangular grating can achieve higher light absorption compared to the rectangular grating. The best top grating is around 200nm grating period, 100nm grating height, and 50% filling factor, which responses to 37% improvement for triangular grating and 23% for rectangular grating compared to non-grating case. Then, we use Finite-Difference Time-Domain (FDTD) to simulate transmission/reflection double grating cases. We simulated triangular-triangular (top-bottom) grating cases and triangular-rectangular (topbottom) grating case. We realize solar cell efficiency improvement about 42.4%. For the triangulartriangular (top-bottom) grating case, the 20% efficiency improvement is achieved. Finally, we present weighted-light simulation for the double grating for the first time and show the best grating can achieve 104% light improvement, which is quite different from traditional non-weighted calculation.

Study of Top Triangular Nano-Grating on Solar Cell Using Rigorous Coupled Wave Analysis

“…It is very hard to judge which period is the best case for the figure. Also for solar cell study, it is very important to consider the Sun spectrum and Silicon photo detector responsivity into our simulation, which are highly wavelength dependent [10]. The weighted factor for solar cell simulation is obtained from the Sun spectrum times Silicon photo detector responsivity with respect of different wavelength.…”

“…At the end of calculation, we obtained the total weighted transmittance by summing all the diffraction efficiencies of the entire wavelength from 300nm to 1100nm according to sum spectrum and Si photodetector responsivity [10]. Compared to other methods, RCWA is a simple and quick method to design the top grating.…”