Uporaba inverzne geometrijske konfiguracije za razvoj senzorskih in elektrokromnih trakov : doktorska disertacija

slovenian

doktorska dela

2020

diffusion   electrochromism   geometry configuration   inverted sandwich   photovoltaics   stainless steel

Univerza v Mariboru, Fakulteta za kemijo in kemijsko tehnologijo

Optoelectronics forms a branch of natural sciences, which studies conversion of light into electrical response and vice versa. Examples include electronic paper (electrical signal converted to light) and solar cells (light conversion into electricity). When discussing electronic paper, we usually focus on electrochromism, while with solar cells are functioning on the principle of photoeffect. Both systems use similar architectures, since they usually both apply at least one optically transparent electrode (OTE), counter electrode and electrolyte, which interacts with the active component applied on the OTE. Optically transparent electrodes represent a bottleneck in the research of new optoelectronic applications, since they have limited specific electrical conductivity, while the manufacturing of this type of electrodes is more expensive than that of metal sheet electrodes. The main limitation of optoelectronic devices so far has been the choice of materials for OTE, as these are limited to glass or plastic carriers with powdered metal or metal oxide coatings and to conductive transparent polymers. Unlike transparent carriers with a conductive substance and conductive polymers, the technology of making metal foils is much older. These metal foils are not transparent, which makes them undesirable in the screen manufacturing industry, but they are distinguished by excellent mechanical and chemical properties as well as exceptional temperature resistance. Metal foils also possess a higher specific conductivity than OTE in almost all cases, which makes them better electrical conductors. It is clear from the scientific literature that all practical electrochromic devices and photosensors need at least one optically transparent electrode. The purpose of the doctoral dissertation is to discover new possibilities on how to build optoelectronic devices, which will use novel geometric configuration. This configuration should be practically applicable to both electrochromic devices as well as to photosensors. Electrochromic device or photosensor, where the non-transparent electrodes are positioned on top of each other with a layer of electrolyte in between, for the purpose of making a device with qualities of semi-transparent optical electrodes is literally impossible to build on existing systems without extensive modifications. It is however possible, to construct such a device, if we build it in a way, where the transparency of the electrode does not form a requirement. Electrochemical systems can be adapted so that they do not require OTE for their operation. In this way, it is possible to assemble electronic paper or solar cells in the form of a tape, flexible plates or thin ropes. The problem with the geometry of the device is the optimization of the electrochemical system itself. This includes finding an appropriate combination of metal electrodes, electrolyte and electrochromic or photovoltaic reactions as well as optimization of the time response, which in most cases depends on the diffusion of ions in the system. The doctoral thesis introduces the use of a new geometric configuration of the "inverse sandwich" in optoelectronic applications and deals with appropriate mechanisms that can operate in the presented configuration. With new geometric approaches, it would be in the future possible to develop new robust electrochemically active fabrics and strips both for the purpose of changing color (electrochromism) and for the purpose of obtaining cheaper electricity or light response detection (photovoltaics).

07.08.2023