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Light Trapping Enhancement in a Thin Film with 2D Conformal Periodic Hexagonal Arrays.

Yang X, Zhou S, Wang D, He J, Zhou J, Li X, Gao P, Ye J - Nanoscale Res Lett (2015)

Bottom Line: 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 %.

View Article: PubMed Central - PubMed

Affiliation: Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China, yangx@nimte.ac.cn.

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.

No MeSH data available.


Photographs and the absorption curves of the four samples. a Photographs of 4-in. wafer-sized samples with infrared wavelength (2300 nm), mid-wavelength (640 nm), and sub-wavelength (300 nm) periodicities as well as a planar reference. b The measured absorption spectra of all four samples. The thickness of the a-Si layer and Ag layer is 160 and 200 nm, respectively
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Fig4: Photographs and the absorption curves of the four samples. a Photographs of 4-in. wafer-sized samples with infrared wavelength (2300 nm), mid-wavelength (640 nm), and sub-wavelength (300 nm) periodicities as well as a planar reference. b The measured absorption spectra of all four samples. The thickness of the a-Si layer and Ag layer is 160 and 200 nm, respectively

Mentions: Figure 4a shows photographs of four a-Si samples, i.e., planar setup and periodically arrayed systems under three configurations (P = 300, 640, and 2300 nm) under an identical film thickness (160 nm). 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 mid-wavelength (sub-wavelength) looks green (dark brown), revealing the strong optical absorption capability. The spectrometer is used to quantitatively characterize the absorption of these samples over a broad range of wavelength (λ) from 300 to 900 nm, which covers most of the solar spectrum. Figure 4b shows the measured absorption spectra of the planar structure and hexagonal arrays with three periodicities. Compared with the planar reference, the films with the periodic arrays demonstrate a significantly improved absorption in the longer wavelength range of 600 nm < λ < 900 nm, where Ag-BSR and the parasitic absorption of Ag are dominating. Within 350 nm < λ < 600 nm, the absorption peaks are ascribed to the Fabry-Perot (FP) cavity modes induced by the stacking structure of air/a-Si/Ag. The resonance wavelength of the FP cavity mode has a redshift with decreasing P. In the shorter wavelength range of λ < 350 nm, there is no significant enhancement of the absorption over the planar reference as the absorption is inherently strong for the a-Si material. It is speculated that the average absorption of the film over the whole wavelength increases when the periodicity migrates from the infrared wavelength range to the sub-wavelength range, which is mainly due to the enhancement of the scattering caused by the Ag-BSR. The experimental result also certifies that the samples with P = 300 nm have an average absorption of 60 %, which is nearly twice that of the planar sample, showing the most outstanding light trapping capability among the three periodic structures.Fig. 4


Light Trapping Enhancement in a Thin Film with 2D Conformal Periodic Hexagonal Arrays.

Yang X, Zhou S, Wang D, He J, Zhou J, Li X, Gao P, Ye J - Nanoscale Res Lett (2015)

Photographs and the absorption curves of the four samples. a Photographs of 4-in. wafer-sized samples with infrared wavelength (2300 nm), mid-wavelength (640 nm), and sub-wavelength (300 nm) periodicities as well as a planar reference. b The measured absorption spectra of all four samples. The thickness of the a-Si layer and Ag layer is 160 and 200 nm, respectively
© Copyright Policy - open-access
Related In: Results  -  Collection

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Fig4: Photographs and the absorption curves of the four samples. a Photographs of 4-in. wafer-sized samples with infrared wavelength (2300 nm), mid-wavelength (640 nm), and sub-wavelength (300 nm) periodicities as well as a planar reference. b The measured absorption spectra of all four samples. The thickness of the a-Si layer and Ag layer is 160 and 200 nm, respectively
Mentions: Figure 4a shows photographs of four a-Si samples, i.e., planar setup and periodically arrayed systems under three configurations (P = 300, 640, and 2300 nm) under an identical film thickness (160 nm). 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 mid-wavelength (sub-wavelength) looks green (dark brown), revealing the strong optical absorption capability. The spectrometer is used to quantitatively characterize the absorption of these samples over a broad range of wavelength (λ) from 300 to 900 nm, which covers most of the solar spectrum. Figure 4b shows the measured absorption spectra of the planar structure and hexagonal arrays with three periodicities. Compared with the planar reference, the films with the periodic arrays demonstrate a significantly improved absorption in the longer wavelength range of 600 nm < λ < 900 nm, where Ag-BSR and the parasitic absorption of Ag are dominating. Within 350 nm < λ < 600 nm, the absorption peaks are ascribed to the Fabry-Perot (FP) cavity modes induced by the stacking structure of air/a-Si/Ag. The resonance wavelength of the FP cavity mode has a redshift with decreasing P. In the shorter wavelength range of λ < 350 nm, there is no significant enhancement of the absorption over the planar reference as the absorption is inherently strong for the a-Si material. It is speculated that the average absorption of the film over the whole wavelength increases when the periodicity migrates from the infrared wavelength range to the sub-wavelength range, which is mainly due to the enhancement of the scattering caused by the Ag-BSR. The experimental result also certifies that the samples with P = 300 nm have an average absorption of 60 %, which is nearly twice that of the planar sample, showing the most outstanding light trapping capability among the three periodic structures.Fig. 4

Bottom Line: 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 %.

View Article: PubMed Central - PubMed

Affiliation: Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China, yangx@nimte.ac.cn.

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.

No MeSH data available.