Abstract
Applying a periodic light trapping array is an effective method to improve the optical properties in thin-film solar cells. In this work, we experimentally and theoretically investigate the light trapping properties of two-dimensional periodic hexagonal arrays in the framework of a conformal amorphous silicon film. Compared with the planar reference, the double-sided conformal periodic structures with all feature periodicities of sub-wavelength (300 nm), mid-wavelength (640 nm), and infrared wavelength (2300 nm) show significant broadband absorption enhancements under wide angles. The films with an optimum periodicity of 300 nm exhibit outstanding antireflection and excellent trade-off between light scattering performance and parasitic absorption loss. The average absorption of the optimum structure with a thickness of 160 nm is 64.8 %, which is much larger than the planar counterpart of 38.5 %. The methodology applied in this work can be generalized to rational design of other types of high-performance thin-film photovoltaic devices based on a broad range of materials.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-0988-y) contains supplementary material, which is available to authorized users.
Highlights
To reduce the usage of materials and the production cost of modules, a substantial amount of researches have been focused on lightweight and mechanically flexible thin-film solar cells (TFSCs)
It is shown that (1) the planar film is mirror-like and highly reflective, (2) the sample with an infrared wavelength periodicity of 2300 nm reflects less, and (3) the sample based on midwavelength looks green, Fig. 3 Realistic photovoltaic systems. a Schematic drawing of a typical 3a depicts the threedimensional (3D) optical model used in the simulations; the Ag film and amorphous silicon (a-Si) film are strictly deposited on the hexagonal periodic nanospheres. b The unit cells of the 300-nm periodic light trapping structure with 160-nm-thick a-Si
To further explore the benefits brought by the conformal hexagonal configuration, the absorption properties of the structures with different thicknesses of the Ag and a-Si films are investigated in detail
Summary
To reduce the usage of materials and the production cost of modules, a substantial amount of researches have been focused on lightweight and mechanically flexible thin-film solar cells (TFSCs). Due to the significantly reduced thickness, the commercially used light trapping structures based on surface texturing and antireflection coating are insufficient for the broadband light absorption of TFSCs [1]. Nanostructures, such as nanobowls, nanoshells, nanocones, and zigzags on the front side [2,3,4,5,6,7,8] and metal nanoparticles (or reflectors) on the back side [9,10,11,12,13,14], have been extensively studied to achieve advanced light trapping through guiding the incident light into the TFSCs or/and the induced localized surface plasmonics and strongly light scattering for the increase of the optical path length. Iftiquar et al investigated a-Si:H solar cells deposited on pyramidally multitextured substrates and achieved a great improvement in the Jsc by 1.3 mA/cm due to a further
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