title: Embedded biomimetic nanostructures for enhanced optical absorption in thin-film solar cells.
abstract: Light-management is critical to thin film solar cells due to their usually limited optical absorption in the active layer. Conventional approaches involve employing separate techniques for anti-reflection and light trapping. Here, we demonstrate an embedded biomimetic nanostructure (EBN) that achieves both effects for hydrogenated amorphous silicon (a-Si:H) solar cells. The fabrication of EBNs is accomplished by patterning an index-matching silicon-nitride layer deposited on a glass substrate using polystyrene nanospheres lithography, followed by reactive ion etching. The profile of EBN is then reproduced layer by layer during the deposition of a-Si:H cells. We show that a solar cell with an optimized EBN exhibits a broadband enhanced external quantum efficiency due to both anti-reflection and light-trapping, with respect to an industrial standard cell using an Asahi U glass substrate which is mostly optimized for light trapping. Overall, the cell with an optimized EBN achieves a large short-circuit current density of 17.74 mA/cm(2), corresponding to a 37.63% enhancement over a flat control cell. The power conversion efficiency is also increased from 5.36% to 8.32%. Moreover, the light management enabled by the EBN remains efficient over a wide range of incident angles up to 60°, which is particularly desirable for real environments with diffused sun light. The novel patterning method is not restricted to a-Si:H solar cells, but is also widely applicable to other thin film materials.
authors: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan.
authors: Min-An
authors: MA
authors: Tsai
authors: Hao-Wei
authors: HW
authors: Han
authors: Yu-Lin
authors: YL
authors: Tsai
authors: Ping-Chen
authors: PC
authors: Tseng
authors: Peichen
authors: P
authors: Yu
authors: Hao-Chung
authors: HC
authors: Kuo
authors: Chang-Hong
authors: CH
authors: Shen
authors: Jia-Min
authors: JM
authors: Shieh
authors: Shiuan-Huei
authors: SH
authors: Lin
mesh_terms: D000042:Absorption; D040761:Biomimetic Materials / Q000737:chemistry*; D011211:Electric Power Supplies; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D055620:Optical Phenomena; D011789:Quantum Theory; D012993:Solar Energy; D013057:Spectrum Analysis