Transport naboja u organskim elektrolitskim fotokondenzatorima

Constructing electronic elements and embedding them into biological tissue for neuronal stimulation represents one of the crucial current challenges in biotechnology and bioelectronics. The optimisation of this process implies the availability of wireless, non-toxic, stable, and biocompatible elements with localised impact. Organic electrolytic photocapacitor is a new electronic element which satisfies these requirements. Before embedding it into biological tissue and its potential commercial deployment, it is necessary to investigate its properties related to electronic transport, and its interaction with biological tissue. There are three possible interactions at the photocapacitor-tissue interface: faradaic, capacitive and mixed, both faradaic and capacitive. Faradaic charge transport considers electrochemical reactions at the photocapacitor-tissue interface. This charge transport type may insert undesirable chemical compounds into a living organism, or damage the electronic components of the photocapacitor. Capacitive charge transfer is safe both for the biological tissue and for the electronic components, but it is limited by the system capacitance. In this thesis we analyse current characteristics of the photocapacitors fabricated in our laboratory. Their active part consists of two thermally evaporated organic semiconducting pigments: metal-free phthalocyanine (H_2Pc - p layer), and perylene diimide derivative (PTCDI - n layer). The pigments are evaporated on the conductive tin-doped indium oxide (ITO) surface. The active part is exposed to light pulses and we aim to profile the generated current based on its faradic or capacitive origin. We fabricate a photocapacitive system immersed into the electrolyte with counter electrodes made of different materials, and then compare and analyse the obtained results. We also analyse how the light pulse length impacts the properties of the current. In order to qualitatively and quantitatively describe faradaic and capacitive processes, we analyse the dynamics of electronic transport. We also provide an insight into oxidation and reduction reactions that occur at the electrolyte interface. Following the measurement results, we propose an equivalent circuit model, and also introduce an analogy between the studied photocapacitors and photodiodes and solar cells.