Light Management in Chiral Optical Metamaterials and Photovoltaic Modules

Abstract

Engineered design of nanophotonic structures enables exemplary control over the generation and propagation of electromagnetic radiation. This thesis explores two promising applications of nanophotonic design, polarization control and photovoltaic light management. Materials with strong and selective interactions with circularly polarized light have wide ranging applications from document security to biological detection. We show that light emitting metasurfaces can be designed with tailored directionality and polarization state of photoluminescence outcoupling through the judicious placement of light emitters within the metasurface’s unit cell. Additionally, the effects of Mie resonances on the circular dichroism (CD) response of a chiral medium are studied. Large CD and dissymmetry factor enhancements are observed by designing the chiral medium to support spectrally overlapping electric and magnetic dipolar resonances. Lastly, the origin of the strong CD responses generated by chiral, single gyroid metamaterials is studied, a metamaterial design that can be fabricated through block copolymer self-assembly templating. The CD responses are found to be dominated by surface interactions, allowing for double gyroid metamaterials, which are achiral in the bulk, to support strong CD responses. The second half of the thesis examines methods to improve the light management in photovoltaic modules. We find that bifacial photovoltaic modules operate at high temperatures due to their increased absorption of rear-side incident light, decreasing their energy yield and operating lifetime. Spectrally selective photonic mirrors that simultaneously provide above-bandgap antireflection and sub-bandgap increased reflection are found to be a promising passive thermal management strategy for bifacial photovoltaics. A spectrally selective mirror is fabricated for outdoor field testing. Lastly, the optical losses in a four-terminal CdTe/Si tandem module are studied and mitigated though rational nanophotonic design.