Transport naboja u organskim elektrolitskim fotokondenzatorima

master's thesis

• Title (english): Charge transport in organic electrolytic photocapacitors
• Author: Katarina Vulić
• Mentor: Vedran Đerek (mentor)
• Committee member: Vedran Đerek (predsjednik povjerenstva)
• Committee member: Hrvoje Buljan (član povjerenstva)
• Committee member: Mario Basletić (član povjerenstva)
• Committee member: Željko Skoko (član povjerenstva)
• Committee member: Nenad Pavin (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2020-07-08, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

Izrada elektroničkih elemenata i njihova implementacija u biološko tkivo u svrhu stimulacije živčanih stanica jedan je od aktualnih izazova biotehnologije i bioelektronike. Optimizacija ovog procesa podrazumijeva postojanje bežičnih, netoksičnih, stabilnih i biološki kompatibilnih elemenata s lokaliziranim djelovanjem. Organski elektrolitski fotokondenzator novi je elektronički element koji zadovoljava sve navedene zahtjeve. Prije implementacije ove vrste elemenata u biološko tkivo i eventualne komercijalne primjene, potrebno je ispitati njegove karakteristike u smislu načina transporta naboja i međudjelovanja s okolinom. Tri su moguće interakcije na granici fotokondenzatora i biološkog tkiva: kapacitivna, faradajska te mješovita, kapacitivna i faradajska. Faradajski prijenos naboja očituje se u postojanju elektrokemijskih reakcija na sučelju tkiva i fotokondenzatora. On je u pravilu nepoželjan jer u organizam potencijalno unosi neželjene spojeve ili pak može uzrokovati oštećenja komponenata fotokondenzatora. Kapacitivni prijenos naboja siguran je i za tkivo i za elektroničke elemente, no ograničen je kapacitetom sustava. U ovom radu analizirat ćemo strujne karakteristike fotokondenzatora izrađenih u našem laboratoriju. Aktivni dio fotokondenzatora sastoji se od dva termalno evaporirana sloja organskih poluvodičkih pigmenata: bezmetalnog ftalocijanina (H_2Pc - p sloj) i derivata perilenskog diimida (PTCDI - n sloj). Pigmenti su evaporirani na vodljivu podlogu od kositrom dopiranog indijeva oksida (ITO). Aktivni dio obasjavat ćemo svjetlosnim pulsevima i pokušati raščlaniti generiranu struju u sustavu na prethodno navedene komponente. Izradit ćemo fotokapacitivni sustav uronjen u elektrolit s protuelektrodama od različitih materijala te međusobno usporediti dobivene rezultate. Promotrit ćemo i kako duljina svjetlosnog pulsa utječe na struju u sustavu. U svrhu kvalitativnog i kvantitativnog opisa kapacitivnih i faradajskih procesa analizirat ćemo dinamiku električnog transporta. Navest ćemo koje su elektrokemijske reakcije redukcije i oksidacije na sučelju elektrolita s komponentama fotokondenzatora potencijalno odgovorne za faradajske procese. Vodeći se rezultatima mjerenja, predložit ćemo i model ekvivalentnog strujnog kruga te povući analogiju fizike fotokondenzatora s fotodiodama i solarnim ćelijama.

Abstract (english)

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.

• Keywords: organski poluvodiči; fotokondenzator; faradajski procesi; kapacitivni procesi; ekvivaletni krug
• Keywords (english): organic semiconductors; photocapacitor; faradaic processes; capacitive processes; equivalent circuit
• Language: croatian
• URN:NBN: urn:nbn:hr:217:098228
• Study programme: Title: Physics; specializations in: Research; Course: Research; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra fizike (magistar/magistra fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2020-08-21 12:46:33