On the Underlying Electronic Transfer of a Photo-Electrode for Developing a Photo-Battery

Abstract

Addressing the current global energy consumption needs and reducing the carbon footprint of primary non-renewable energy resources are key challenges of the 21st century. Solar energy is among one of the best suited candidates to address this along with the current global energy needs. This is because sunlight produces no greenhouse emissions. A major challenge that must be overcome before the benefits of solar energy can be truly realized is the storage of sunlight for use during dark periods. Devices that convert, store, and deliver the stored solar energy during dark periods are therefore of importance.Lithium-ion batteries are proven technologies. They have a high energy density along with a long cycle life. Indeed, they have been successfully coupled to silica-based solar cells such as photovoltaic panels. To expand upon the proven solar-battery technologies and move towards self-sustaining and portable energy devices, our current efforts focus on merging a lithium-ion battery with a photoactive organic dye. The working principle of this all-in-one device is the energy harvesting of sun light by an organic dye and storing the harvesting energy as chemical energy, courtesy of redox reactions that are specific to the lithium-ion battery.The organic dye of choice was selected because it satisfies many of the physical and electrochemical requirements for its use in an integrated photobattery. For example, it possesses an intrinsic broad absorption in the visible spectrum, has a high degree of colorfast, and is photostable. Despite these key properties that are ideal for its use in a photobattery, this dye has not been used as the photoactive layer in a photobattery. In addition, many LIB electrode materials that meet the energetic requirements to be paired with the dye need to be screened.Towards demonstrating the compatibility of the dye-battery active material, the photoreduction of the dye by the battery’s electroactive component will be demonstrated in solution by fluorescence spectroscopy. Both steady-state and time-resolved quenching measurements will be presented as sound evidence of the underpinning electron transfer between the constitutional “solar” and “battery” components. Various common electrode materials have also been screened to provide key knowledge about the materials’ property requirements to sustain intermolecular electronic transfer. Different architectures of photo-electrodes will also be explained and evaluated for an optimal electronic transfer. Steady-state quenching measurements and Raman spectroscopy will be shown to broaden the understanding of the interfacial electron transfer processes.Electrochemical studies will also be presented to complement the photophysical investigation, including galvanostatic cycling with the dye using various photo-cathode architectures. These were investigated to understand the role of the microstructure on the electronic transfer.The collective studies will provide sound evidence that both the photoactive and batteries technologies can be successfully merged, laying the experimental groundwork for an all-in-one photobattery. Towards realizing the true ecological potential of the battery, it will be presented that its conventional organic electrolytic solvents can be replaced with environmentally benign water.