Optimal design of periodic surface texture for thin-film a-Si:H solar cells

Optical analysis of hydrogenated amorphous silicon (a-Si:H) solar cells with a periodic texture applied to the interfaces was carried out by two-dimensional optical simulator. The optical simulator solves the electromagnetic wave equations by means of finite element method using triangular elements for the discretization of space. The periodic texture with rectangular-like shape acts as a diffraction grating which scatters light into selective angles and thus gives a potential for significant prolongation of optical paths in thin absorber layers of the cells. Optimization of the geometrical parameters (period, height and duty-cycle) of the periodic texture was carried out in order to obtain the highest photocurrent from a-Si:H solar cells. The a-Si:H solar cell with the optimal periodic texture parameters (period of 300¿nm, height of 300¿nm and duty cycle of 50%) and the absorber layer thickness of 300¿nm generates up to 35% more photocurrent in comparison to the cell with flat interfaces. The optical analysis demonstrates that the optimal periodic texture in the a-Si:H solar cell results in the best trade-off between the antireflection effect at front interfaces, light scattering efficiency and the absorption losses at realistic metal back contact.