Barium titanate (BaTiO 3 , BTO) is a perovskite class material of remarkable dielectric, ferroelectric and ferromagnetic properties. Our previous studies on optical properties of BTO thin films proved high visible transmittance and sharp absorption edge at ~ 300 nm. Therefore the usage of BTO as a UV blocker or an antireflection (AR) coating in visible region is straightforward. AR coatings are agreed to be important parts of many photonic devices, among them also of solar cells. In this paper, single layers of amorphous BTO are numerically and experimentally investigated as promising AR coatings for achieving increased light trapping in thin film silicon solar cells. Reduced reflections achieved by BTO thin films deposited using RF magnetron sputtering on a-Si:H/SiO 2 compared with pristine a-Si:H/SiO 2 system are clearly demonstrated. Antireflection effects are analyzed using simple AR systems comprising BTO.
We have synthesized silicon nanocrystalline structures from thermal annealing of thin film amorphous silicon-based multilayers. The annealing procedure that was carried out in vacuum at temperatures up to 1100°C is integrated in a X-ray diffraction (XRD) setup for real-time monitoring of the formation phases of the nanostructures. The microstructure of the crystallized films is investigated through experimental measurements combined with atomistic simulations of realistic nanocrystalline silicon (nc-Si) models. The multilayers consisting of uniformly alternating thicknesses of hydrogenated amorphous silicon and silicon oxide (SiO 2 ) were deposited by plasma enhanced chemical vapor deposition on crystalline silicon and Corning glass substrates. The crystallized structure consisting of nc-Si structures embedded in an amorphous matrix were further characterized through XRD, Raman spectroscopy, and Fourier transform infrared measurements. We are able to show the different stages of nanostructure formation and how the sizes and the crystallized mass fraction can be controlled in our experimental synthesis. The crystallized silicon structures with large crystalline filling fractions exceeding 50% have been simulated with a robust classical molecular dynamics technique. The crystalline filling fractions and structural order of nc-Si obtained from this simulation are compared with our Raman and XRD measurements.
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