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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.


Realistic photovoltaic systems. a Schematic drawing of a typical 3D optical model used in the simulations (not to scale); the Ag film (green) and a-Si film (orange) are strictly deposited on the hexagonal periodic nanospheres (gray). b The unit cells of the 300-nm periodic light trapping structure with 160-nm-thick a-Si. The PS spheres in b are not indicated because the Ag film is thick enough to prevent light from transmitting
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Fig3: Realistic photovoltaic systems. a Schematic drawing of a typical 3D optical model used in the simulations (not to scale); the Ag film (green) and a-Si film (orange) are strictly deposited on the hexagonal periodic nanospheres (gray). b The unit cells of the 300-nm periodic light trapping structure with 160-nm-thick a-Si. The PS spheres in b are not indicated because the Ag film is thick enough to prevent light from transmitting

Mentions: To further characterize the light trapping effect related to the surface topography and the feature sizes of the structures, the optical behaviors are examined through numerical simulation. Figure 3a depicts the three-dimensional (3D) model of the conformal structures with periodic hexagonal configurations investigated in our simulation. For convenience, we have assumed that the Ag and a-Si films are strictly deposited on the close-packed periodic hexagonal PS nanospheres without any defects, and the configurations are rigorously conformal from bottom to top. The unit cell of the optimized structure is shown in Fig. 3b. The thickness of the a-Si layer is 160 nm, and the periodicity of the hexagonal array is 300 nm, as can be verified from Fig. 2. The incident light is a plane wave with a polar angle, θ, and an azimuthal angle, φ. The light wavelength, λ, is chosen from 300 to 900 nm to match the a-Si absorption band. The layer thicknesses are taken from the cross sections of SEM and SPM measurements in Fig. 2. The optical index of a-Si is based on the ellipsometry measurement (Additional file 1), and the optical parameter of Ag is based on the Palik data [27]. Both the transverse electric (TE) and transverse magnetic (TM) polarizations are simulated. The simulations are performed by finite element method within a unit configuration surrounded by the periodic boundaries along the lateral direction [28]. The perfectly matched layers (PML) are implemented along the incident direction to prevent interference effect. The detailed energy flux distribution inside the structures is calculated under the solar spectrum at air mass 1.5 [29]. The absorption and the reflection at each wavelength are calculated with an interval of 10 nm.Fig. 3


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)

Realistic photovoltaic systems. a Schematic drawing of a typical 3D optical model used in the simulations (not to scale); the Ag film (green) and a-Si film (orange) are strictly deposited on the hexagonal periodic nanospheres (gray). b The unit cells of the 300-nm periodic light trapping structure with 160-nm-thick a-Si. The PS spheres in b are not indicated because the Ag film is thick enough to prevent light from transmitting
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4495099&req=5

Fig3: Realistic photovoltaic systems. a Schematic drawing of a typical 3D optical model used in the simulations (not to scale); the Ag film (green) and a-Si film (orange) are strictly deposited on the hexagonal periodic nanospheres (gray). b The unit cells of the 300-nm periodic light trapping structure with 160-nm-thick a-Si. The PS spheres in b are not indicated because the Ag film is thick enough to prevent light from transmitting
Mentions: To further characterize the light trapping effect related to the surface topography and the feature sizes of the structures, the optical behaviors are examined through numerical simulation. Figure 3a depicts the three-dimensional (3D) model of the conformal structures with periodic hexagonal configurations investigated in our simulation. For convenience, we have assumed that the Ag and a-Si films are strictly deposited on the close-packed periodic hexagonal PS nanospheres without any defects, and the configurations are rigorously conformal from bottom to top. The unit cell of the optimized structure is shown in Fig. 3b. The thickness of the a-Si layer is 160 nm, and the periodicity of the hexagonal array is 300 nm, as can be verified from Fig. 2. The incident light is a plane wave with a polar angle, θ, and an azimuthal angle, φ. The light wavelength, λ, is chosen from 300 to 900 nm to match the a-Si absorption band. The layer thicknesses are taken from the cross sections of SEM and SPM measurements in Fig. 2. The optical index of a-Si is based on the ellipsometry measurement (Additional file 1), and the optical parameter of Ag is based on the Palik data [27]. Both the transverse electric (TE) and transverse magnetic (TM) polarizations are simulated. The simulations are performed by finite element method within a unit configuration surrounded by the periodic boundaries along the lateral direction [28]. The perfectly matched layers (PML) are implemented along the incident direction to prevent interference effect. The detailed energy flux distribution inside the structures is calculated under the solar spectrum at air mass 1.5 [29]. The absorption and the reflection at each wavelength are calculated with an interval of 10 nm.Fig. 3

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.