Dielectric gratings for efficient light trapping in thin-film silicon solar cell

Efficient light trapping structure is needed for thin film silicon solar cell. We have investigated that dielectric diffraction grating structures have the potential to increase the efficiency by excellent light absorption. In order to boost up the efficiency of the solar cell optimized diffraction grating is designed which cause the optical path length enhancement within the silicon (Si) absorber layer. In our simulation Si square grating and titanium oxide (TiO₂) pyramid grating is integrated separately on the illuminated surface of a 3.0 μm - thick-solar cell. Numerical simulation is performed with Finite Difference Time Domain (FDTD) method over a wavelength range of 400-1100 nm. The resultant potential short circuit current density is compared with the planar and ideal Lambertian case. Solar cell with TiO₂ pyramid diffraction grating on the front surface results better light trapping than the cell with Si square grating. Simulation result shows that TiO₂ pyramid grating provides a short circuit current density, Jsc, of 24.7mAcm^-2 which is 67.2% of ideal Lambertian case.