Issue 32, 2015

Antireflective gradient-refractive-index material-distributed microstructures with high haze and superhydrophilicity for silicon-based optoelectronic applications

Abstract

We fabricate gradient-index (n) material-based microstructures, i.e., magnesium fluoride (MgF2, n ∼ 1.37) film-coated SU8 ultraviolet curable polymer (n ∼ 1.59) microcones (MCs) with tapered architectures, on silicon (Si, n ∼ 3.9) substrates using a soft imprint lithography method for high-performance Si-based optoelectronic applications. The effects of various geometry parameters (i.e., height, filling ratio, and period) of conical MCs on the SU8 film/Si structure including different thicknesses of MgF2 films on the reflectance properties are investigated by a theoretical analysis using a rigorous coupled-wave analysis simulation. For the fabricated samples, their optical characteristics and surface wetting behaviors are also explored. The MgF2 film-coated SU8 MCs on Si substrates (i.e., MgF2/SU8 MCs/Si) exhibit a superhydrophilic surface with very low water contact angles of <10° and reduce the surface reflection of the bare Si over a wide wavelength of 350–1100 nm, showing the lower average reflectance (Ravg) and solar weighted reflectance (Rsw) values of ∼14% and ∼12.1%, respectively, (i.e., Ravg ∼ 15.1% and Rsw ∼ 13% for the SU8 MCs/Si and Ravg ∼ 38.5% and Rsw ∼ 38% for the bare Si). Furthermore, the MgF2/SU8 MCs on glasses also show strong light scattering in transmissions at wavelengths of 350–1100 nm, which indicates an average haze ratio of ∼89.8%, while maintaining high total transmissions. Both the measured and calculated reflectance spectra showed similar results.

Graphical abstract: Antireflective gradient-refractive-index material-distributed microstructures with high haze and superhydrophilicity for silicon-based optoelectronic applications

Article information

Article type
Paper
Submitted
03 Dec 2014
Accepted
02 Mar 2015
First published
11 Mar 2015
This article is Open Access
Creative Commons BY license

RSC Adv., 2015,5, 25616-25624

Author version available

Antireflective gradient-refractive-index material-distributed microstructures with high haze and superhydrophilicity for silicon-based optoelectronic applications

M. Choi, J. W. Leem and J. S. Yu, RSC Adv., 2015, 5, 25616 DOI: 10.1039/C4RA15686B

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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