Enhanced Light Trapping in a-Si:H/μc-Si:H Tandem Solar Cells via Nanopatterning Top Absorber and Embedding Wavelength-Selective Intermediate Reflectors

Output photocurrent of a-Si:H/μc-Si:H tandem solar cells is usually determined by the unsatisfactory absorption of a-Si:H layer restricted by its thin thickness required by the very limited carrier diffusion length and low absorption coefficient at wavelengths over 550 nm. In this paper, we present a new configuration to enhance the light-trapping performance and the output photocurrent of a-Si:H/μc-Si:H tandem solar cells via the nanopatterning a-Si:H layer and embedding wavelength-selective intermediate reflector layer (WSIRL) between the top and bottom cells. Our simulations indicate that absorption and photocurrent of the tandem cells in the proposed scheme exhibit a significant and wide-angle enhancement compared with the planar cases with or without WSIRL and the nanopatterned case without WSIRL. An ultimate photocurrent density, which is obtained under normally incident AM1.5G solar irradiation and ideal internal quantum efficiency, is 37.56% higher than that of the planar counterpart with a normal ZnO intermediate reflector. Moreover, the attenuation ratio of the output photocurrent in the proposed configuration is only 2.95% when the incident angle alters from 0° to 60°.