Browsing by Subject "Solar-cells"
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Item The development of scalable, self-assembled, low-cost nanophotonic structures for enhanced photocurrent generation for light-weight, portable, and high-efficiency III-V solar cells(2021-01-21) Cossio, Gabriel; Yu, Edward T.; Korgel, Brian A; Bonnecaze, Roger T; Sreenivasan, S V; Bank, Seth RNanosphere lithography is a versatile and low-cost method for defining two dimensional periodic lithographic patterns on the nanoscale. However, nanosphere lithography suffers from a lack of scalability that has prevented its low-cost nature from being successfully integrated into any commercialized processes. This dissertation investigates methods to improve the scalability of nanosphere lithography in order to enable the development of low-cost nanophotonic light management structures which increase the photogenerated current in portable, light-weight, high-efficiency III-V solar cells. A new physical model for monolayer self-assembly via the injection of colloidal nanoparticles onto an air-water interface is presented. The physical model is verified by experiment and shows that particle-particle interactions play an important role in increasing the growth rate of self-assembled nanoparticle monolayers on an air-water interface. Experiments show that by increasing particle closeness, as measured by the magnitude of the zeta potential, a ~7x improvement in monolayer growth-rate can be achieved. The physical model is verified for the injected self-assembly of polystyrene and SiO2 nanospheres monolayers, as well as for particles in the range of 200 nm – 2μm. Experimental techniques are presented for the successful transfer of large area (>200cm2) self-assembled nanosphere monolayers onto rigid or flexible substrates, demonstrating that the scalability of nanosphere lithography is in fact possible. The improved nanosphere lithography method is utilized to fabricate large-area moth-eye nanopatterned on PET polymer packaging sheets for flexible solar modules. The moth-eye textured PET sheets are optically characterized and are shown to provide broadband, omnidirectional reduction in specular and diffuse reflectance. The moth-eye textured PET sheets are shown to survive an industrial lamination procedure and are utilized to encapsulate a light-weight, portable, flexible solar module made from an array of triple junction III-V based epitaxial lift-off solar cells. Maximum photogenerated current enhancement due to the omnidirectional antireflection properties of the moth-eye textured encapsulant is measured to be ~60% higher at ~80o angle of incidence relative to a solar module without any nanotexturing of the PET packaging layer. Lastly, future work that can benefit from the enhanced nanosphere lithography method are outlined, particularly the fabrication of low-cost self-assembled light trapping structures.