Characterization of faradaic and capacitive processes in organic photoelectrodes for artificial retina prosthesis

An increasing number of studies about artificial retinal prothesis have been carried out recently demonstrating the possibility to restore sight in partially sighted or blind patients. In all of such devices the fundamental component is an opotobioelectronic layer. When illuminated, this layer produces ionic current pulses of enough intensity to activate the visual cortex’s neurons. The principal objective to achieve is the deep understanding of the processes that occur at the semiconductor-liquid interface, with the purpose to develop materials that present flexibility and biocompatibility and are not subject to deterioration when in contact with an acqueous electrolyte. In this thesis I have analysed organic semiconducting pigments developed by the Linkoping University as active optobioelectronic layer. The purpose of the thesis is to investigate and characterize the faradaic and capacitive processes that occur at the interface when a light stimulated current pulse is generated. The results show that faradaic processes are favoured by a negative potential applied to the optobioelectronic layer, while with a positive potential the photocurrent is almost completely capacitive. The wavelength of the stimulating light pulse has instead no significant effect on the ratio between capacitive to faradaic current generation processes.