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Solution-Processed Fabrication of One-Dimensional Photonic Crystals: Demonstrating Device Tunability and Perovskite Compatibility for Scalable, Efficient Optoelectronics


As global power consumption continues to rapidly increase the need for efficient, economically feasible, and environmentally conscious energy sources has become clear. In accordance with these sustainable efforts, the presented dissertation details the development of an entirely solution-processed Distributed Bragg Reflector (DBR) continuum which circumvents the energy intensive processes usually needed to fabricate these optoelectronic environments. These mirrors were created through alternative spincoating of titania sol gel and polymethyl methacrylate (PMMA) films atop a glass substrate. A series of tests were conducted to derive a model for the effective titania sol gel film refractive index as a function of wavelength, as this quantity is highly dependent on experimental workup. Atomic force microscopy measurements have confirmed that these individual layers are sufficiently thin (on the order of hundreds of nanometers) and thus the resulting DBR structures have the desired thicknesses (on the order of micrometers) for use in real device applications. The reflectance spectra for these mirrors contain well-defined photonic bandgaps that span nearly 400 nm of the visible light wavelength regime, and retain peak heights on the order of 90%. These attributes make the reflectors suitable for use in lasing, LED, and next-generation solar device applications. Following the success of the DBR continuum, an entirely solution-processed luminescent solar concentrator design was formulated: green-emitting photoluminescent nanocrystals placed between two green-reflecting DBR mirrors. In-air, room temperature CsPbBr3 perovskite syntheses produced nanocrystals with narrow emission bands in this regime that possessed all of the expected absorbance and photoluminescence spectra features. Preliminary work was done to stabilize these perovskites between two titania sol gel films - their effective local environment in the luminescent solar concentrator design that largely extinguishes any emission from these crystals. Power measurements taken inside an integrating sphere setup exemplified the preliminary success of using polystyrene to interface between the nanocrystals and surrounding titania films in this role. Future directions hope to improve upon this result, as well as continue to optimize the DBR mirror geometry. Following the eventual success of the green luminescent solar concentrator, attention will be given to other color domains in pursuit of the ultimate goal of this study: transforming the present DBR continuum into an entirely solution-processed luminescent solar concentrator continuum to be used as a basis for multijunction solar cell design.

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