Dataset Information

Optically Graded Ultra Dark Absorber for Visible and Near-infrared Wavelength Range.

ABSTRACT: Near perfect absorbers find application in many areas including solar cells, energy harvesting and antireflection coatings for space applications. Here we report the use of optical gradation concept to fabricate a near perfect absorber on etched Si wafer. As a proof of concept, 99.4% absorption is achieved in the broad range of 300?nm to 2000?nm. Moreover, absorption capacity of optically graded surface remains higher than 99% up to beam incident angle of 50°. While carbon nanotubes (index ~1.1) are used as top layer, subsequent layers with increasing optical index across the thickness are chosen so as to satisfy zero reflection condition on multilayered assembly. Inward bending of incident beam and total internal reflection of reflected beam caused due to optical index gradient contributes to absorb the incident beam more efficiently. In addition, multiple scattering of incident beam due to the presence of multiscale feature size in graded assembly helps to absorb shorter as well as longer wavelengths of incident light. The graded assembly shows contact angle of 160° with roll-off angle equal to 5° implying that the graded absorber is not only super black but also superhydrophobic and self-cleaning in nature. The combination of properties shown by the super absorber makes it very attractive, especially for next generation solar cells to harness energy in the wavelength range of 1000?nm to 2000?nm.

SUBMITTER: Agnihotri PK

PROVIDER: S-EPMC6098028 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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Optically Graded Ultra Dark Absorber for Visible and Near-infrared Wavelength Range.

Agnihotri Prabhat K PK Ghai Viney V Singh Harpreet H

Scientific reports 20180817 1

Near perfect absorbers find application in many areas including solar cells, energy harvesting and antireflection coatings for space applications. Here we report the use of optical gradation concept to fabricate a near perfect absorber on etched Si wafer. As a proof of concept, 99.4% absorption is achieved in the broad range of 300 nm to 2000 nm. Moreover, absorption capacity of optically graded surface remains higher than 99% up to beam incident angle of 50°. While carbon nanotubes (index ~1.1) ...[more]

PMID: 30120373

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Project description:Soil salinization is the primary obstacle to the sustainable development of agriculture and eco-environment in arid regions. The accurate inversion of the major water-soluble salt ions in the soil using visible-near infrared (VIS-NIR) spectroscopy technique can enhance the effectiveness of saline soil management. However, the accuracy of spectral models of soil salt ions turns out to be affected by high dimensionality and noise information of spectral data. This study aims to improve the model accuracy by optimizing the spectral models based on the exploration of the sensitive spectral intervals of different salt ions. To this end, 120 soil samples were collected from Shahaoqu Irrigation Area in Inner Mongolia, China. After determining the raw reflectance spectrum and content of salt ions in the lab, the spectral data were pre-treated by standard normal variable (SNV). Subsequently the sensitive spectral intervals of each ion were selected using methods of gray correlation (GC), stepwise regression (SR) and variable importance in projection (VIP). Finally, the performance of both models of partial least squares regression (PLSR) and support vector regression (SVR) was investigated on the basis of the sensitive spectral intervals. The results indicated that the model accuracy based on the sensitive spectral intervals selected using different analytical methods turned out to be different: VIP was the highest, SR came next and GC was the lowest. The optimal inversion models of different ions were different. In general, both PLSR and SVR had achieved satisfactory model accuracy, but PLSR outperformed SVR in the forecasting effects. Great difference existed among the optimal inversion accuracy of different ions: the predicative accuracy of Ca2+, Na+, Cl-, Mg2+ and SO4 2- was very high, that of CO3 2- was high and K+ was relatively lower, but HCO3 - failed to have any predicative power. These findings provide a new approach for the optimization of the spectral model of water-soluble salt ions and improvement of its predicative precision.

Dataset Information

Optically Graded Ultra Dark Absorber for Visible and Near-infrared Wavelength Range.

Publications

Optically Graded Ultra Dark Absorber for Visible and Near-infrared Wavelength Range.

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