Broadband light trapping with disordered photonic structures in thin-film silicon solar cells

We theoretically investigate light trapping with disordered 1D photonic structures in thin-film crystalline silicon solar cells. The disorder is modelled in a finite-size supercell, which allows the use of rigorous coupled-wave analysis to calculate the optical properties of the devices and the short-circuit current density Jsc. The role of the Fourier transform of the photonic pattern in the light trapping is investigated, and the optimal correlation between size and position disorder is found. This result is used to optimize the disorder in a more effective way, using a single parameter.We find that a Gaussian disorder always enhances the device performance with respect to the best ordered configuration. To properly quantify this improvement, we calculate the Lambertian limit to the absorption enhancement for 1D photonic structures in crystalline silicon, following the previous work for the 2D case [M.A. Green, Progr. Photovolt: Res. Appl. 2002; 10(4), pp. 235–241]. We find that disorder optimization can give a relevant contribution to approach this limit. Finally, we propose an optimal disordered 2D configuration and estimate the maximum short-circuit current that can be achieved, potentially leading to efficiencies that are comparable with the values of other thin-film solar cell technologies.