Biomimetic broadband antireflection gratings on solar-grade multicrystalline silicon wafers

Abstract

We report a simple and scalable bottom-up technique for fabricating broadband antireflection gratings on solar-grade multicrystalline silicon (mc-Si) wafers. A Langmuir-Blodgett process is developed to assemble close-packed silica microspheres on rough mc-Si substrates. Subwavelength moth-eye pillars can then be patterned on mc-Si by using the silica microspheres as structural template. Hemispherical reflectance measurements show that the resulting mc-Si gratings exhibit near zero reflection for a wide range of wavelengths. Both experimental results and theoretical prediction using a rigorous coupled-wave analysis model show that close-packed moth-eye arrays exhibit better antireflection performance than non-close-packed arrays due to a smoother refractive index gradient. V

An infrared high resolution silicon immersion grating spectrometer for airborne and space missions

“…3.4) appears dark at nearly all viewing angles, indicating an excellent wide-angle AR performance. This result is further confirmed by angleresolved reflection and hemispherical reflection measurements 15 . Moreover, the optical reflection measurements match well with the numerical simulations using the RCWA model.…”

“…The optimal moth-eye AR gratings on a SIG silicon disk are being fabricated by both standard top-down photolithography and nontraditional bottom-up colloidal lithography 11,13,14,15 . Figure 3.3 shows a schematic illustration of these two approaches.…”

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“…134 A simple and potentially roll-to-roll compatible LB particle self-assembly technology has thus been developed to assemble close-packed monolayer colloidal crystals on curved and/or rough surfaces. 115 Nanoparticle antiglare coatings have recently been demonstrated on glass substrates by using this bottom-up technology. 135 Monodispersed silica spheres with diameter ranging from ∼110 nm to ∼30 µm are purified by repeated centrifugation/redispersion cycles in ethanol and are finally redispersed in ethylene glycol with particle volume fraction of 0.20.…”

“…14A and 14B). 115 Importantly, the different crystalline orientations (or domains) of mc-Si wafers do not significantly affect the dry etching rate of silicon during RIE. 116 The specular hemispherical reflectance spectra obtained from a polished sc-Si wafer, a solar-grade mc-Si wafer, and the templated mc-Si grating are compared in Fig.…”

“…1). To resolve the outstanding issues of current colloidal self-assembly and templating nanofabrication, two scalable bottom-up technologies based on spin-coating 102−114 and LB assembly of colloids at a water-air interface 115 have been developed. Spin-coating enables rapid production of colloidal crystals with remarkably large domain sizes and unusual nonclose-packed structures; whereas LB assembly allows for wafer-scale production of close-packed colloidal single crystals.…”