Absorption Enhancement by Light Scattering for Solar Energy Applications

In this thesis, I discuss few novel approaches to enhance the light-matter interaction, which have applications in solar energy. Enhancement of absorption/ fluorescence is a topic of immense interest in recent years for its importance in various fields: bio-sensing and diagnostics, solar energy, imaging, forensics, etc.. Often, applications involving fluorescence are quite low efficient, and which is mainly attributed to poor fluorescence from constituent fluorescent molecules. Enhancing fluorescence of molecules can enable to realize very efficient applications. And, one such application which needs attention is Luminescent solar concentrator, which is a main topic of discussion in this thesis. Luminescent solar concentrators (LSCs) are polymer slabs filled with fluorescent molecules which absorb incoming sunlight and emit fluorescence inside the slab, and which is partially guided to the edges where photovoltaic cells are attached. Poor absorption/fluorescence of organic molecules is due to their intrinsic chemical structure, due to which either they display huge non-radiative decay losses or poor absorption efficiency, etc.. It is well know that the amount of light emitted by molecules also depends on their surrounding medium properties. Modifying the surrounding environment very close to the molecules can actually modify the intrinsic fluorescence properties of molecules. This idea has been applied quite a lot to modify the properties of molecules close to metallic nanostructures/nanoparticles. When it comes to enhance the fluorescence of molecules embedded in polymer slabs like LSCs all existing approaches fail to work. In thesis, I discuss elaborately, in particular answering following questions: why existing approaches fail to work, essentially what kind of approaches are needed, and how they should be implemented.