Templated Subwavelength-Structured Antireflection Coatings

1. Templated Subwavelength-Structured Antireflection Coatings for High-Efficiency Crystalline Silicon Solar Cells Peng Jiang, Department of Chemical Engineering, University of Florida Because of the high refractive index of silicon, more than 30% of incident light are reflected back from crystalline silicon, thus greatly impeding the conversion efficiency of Si photovoltaic devices. This proposal will develop an inexpensive and scalable templating approach to fabricate broadband moth-eye antireflection coatings. We have successfully demonstrated several templating technologies for fabricating subwavelength-structured moth-eye antireflection coatings (ARCs) on a large variety of technologically important substrates, including Si, GaAs, GaSb, and glass. The templated moth-eye antireflection coatings exhibit much improved broadband antireflection properties than traditional quarter-wavelength dielectric coatings. Normal-incidence reflection of less than 2% can be achieved on silicon, GaAs and GaSb substrates. Optical reflection of less than 1% for all optical wavelengths can be achieved for polymer and glass ARCs on transparent substrates.The moth-eye coating also exhibits superhydrophobic surface state once the aspect ratio of the nanopillars is higher than 10. This is important for developing self-cleaning ARCs for solar cells and many other optoelectronic devices. We have also developed two theoretical models – RCWA and TFM to simulate the optical reflection, transmission, and diffraction from the templated subwavelength-structured ARCs. These models help better understanding of the optical diffraction from subwavelength gratings, as well as rational design of moth-eye antireflection coatings for different applications. We have shown that the RCWA and TFM models create almost equivalent results for subwavelenth-structured moth-eye gratings. Colloidal Crystal Template Templated Si Moth-eye ARC Excellent Broadband Antireflection