A novel trapezoidal profile of optimized diffraction grating for light trapping in thin silicon solar cells

In this paper, we propose a new design and comprehensive optimization process for improving the diffraction gratings used as the back reflector of silicon solar cells. For this process, the optimum refractive index and its corresponding available material which can be used as the grating material has been chosen as 1.57 and SiO₂, respectively. Also, all of geometric parameters which affect the performance of the grating, such as periodicity, height and depth of grating profiles have been studied and the appropriate values for each of them have been proposed. In order to optimize the profile of grating, a transition from triangular to rectangular structure has been considered and finally a specific trapezoidal profile has been chosen as the optimized grating back reflector which enhances the cell efficiency up to 6%. Simulation results show that the different grating profiles have the same duty cycle and therefore use the same amounts of materials.