Effect of nanostructured architecture on the enhanced optical absorption in silicon thin-film solar cells

We apply the finite-difference time-domain method to numerically calculate the enhanced optical absorption of three nanostructures (i.e. nanorod, nanocone, and nanolens arrays) that were decorated on the surface of 2 mu m thick crystal silicon (Si) thin-films. Compared with the nanorod and nanocone arrays, the nanolens array exhibits the highest power conversion efficiency. This result is mainly attributed to the natural capability of the nanolens array to optically couple incident light into in-plane guided modes, which increases the optical path of the incident photons in the long-wavelength regime. The power conversion efficiencies of the optimized nanorod, nanocone, and nanolens arrays are eta = 17.4, 18.8, and 22.0%, respectively. These efficiencies correspond to enhancements of 26.1, 36.2, and 59.4% for the nanorod, nanocone, and nanolens arrays, respectively, compared with a planar Si thin-film with a standard quarter-wavelength antireflection layer. These findings show promises for the nanostructured design of Si thin-film solar cells that exhibit enhanced optical absorption.