Broadband optical absorption enhancement of hexagonal nanoconical frustum arrays texturing for c-Si film solarcells

In this paper, the optical properties of the silicon hexagonal nanoconical frustum (SiHNF) arrays are theoretically studied via simulation based on the Rigorous Coupled Wave Analysis (RCWA) in detail. The results show that the SiHNF bottom diameter (Dbot) should be equal to the array periodicity for efficient solar energy harvesting, and the optimized light absorption could be realized when the SiHNF height reaches 1000 nm with Dtop equal to100 nm. The optimal SiHNF arrays has the periodicity of 700 nm, the top diameter of 100 nm and the SiHNF height of 1000 nm, yielding an ultimate efficiency of 30.54%, which is more than two times of a 2.33 μm thick Si thin film solar cells. Comparing to nanopillar and square nanoconical frustum structures, the enhanced ultimate efficiency of SiHNF structure is less sensitive to the incident zenith angle and SiHNF top diameter. The possible physical mechanism behind the observation is also explored in thiswork.