Conductive and flexible nanocomposites can have wide applications in textiles, including wearable sensors, antenna, electrodes, etc. The objective of this research is to develop electrically conductive fibers and films that are flexible and deformable for use in textile structures able to accommodate the drape and movement of the human body. To achieve this objective, we evaluate the electrical properties of PEDOT:PSS/nickel nanostrand as well as nylon 6/nickel nanostrand nanocomposites. Nickel nanostrands (NiNS) were first used to reinforce an intrinsically conductive polymer, Poly(3,4-ethylenedioxythiophene) (PEDOT:PSS), in order to fabricate nanocomposite films with high electrical conductivity. The electrical properties of the films were evaluated by the Van der Pauw method. The addition of 10 wt% nanostrands in PDOT:PSS provided a two order of magnitude improvement in electrical conductivity. In addition to PDOT:PSS, nylon 6/NiNS nanocomposite fibers were produced using electrospinning and exhibited diameters in the sub-micron range. The NiNS-reinforced fibers had electrical conductivity that exceeded the ESD range, which offers the potential for use in protective textile applications. / text

O presente trabalho apresenta resultados de preparação, caracterização e aplicação de membranas de DNA e DNA-PEDOT:PSS como material transportador de buracos (HTM) em células solares sensibilizadas por corante (DSSC). As análises por UV-Vis das amostras revelaram 80% de transparência em 600 nm para o DNA-isolado e diminuindo para 62% em 550 nm para o DNA-2% PEDOT:PSS. As análises das amostras por FTIR revelaram os picos característicos tanto do DNA quanto do PEDOT:PSS, confirmando a incorporação deste último nas membranas. Os resultados de análises térmicas DSC evidenciaram a presença de Tg em -67ºC e o seu desaparecimento com a adição de PEDOT:PSS na formulação de HTM. As análises de TGA mostraram o aumento da estabilidade das amostras com a adição de PEDOT:PSS atingindo 200ºC. Todas as amostras apresentaram 19% de resíduos em 900ºC. As membranas a base de DNA também foram submetidas às medidas de condutividade iônica revelando o maior valor de 3,2x10-4 S/cm2 em temperatura ambiente e aumentando para 0,1x10-3 S/cm2 em temperatura de 75ºC, para a amostra de DNA-isolado. As amostras de DNA-PEDOT:PSS mostraram valores de condutividade de 4,67x10-5 S/cm2 para a amostra DNA -2% PEDOT:PSS, em temperatura ambiente e diminuíram com o aumento de porcentagem de PEDOT:PSS. Dos difratogramas de raios-X observou-se um aumento da cristalinidade das amostras com a adição de PEDOT:PSS sendo o maior valor encontrado de 77,8% foi para a amostra de DNA-10% PEDOT:PSS. As DSSCs apresentaram a diminuição de eficiência solar após a introdução de membranas de DNA de 2.04% para 1,49% fenômeno explicado em termos de aumento de reflectância e rugosidade das amostras que dificultou o transporte de carga e recombinação do par redox do eletrólito nas células solares sensibilizadas por corante. / This paper presents results of preparation, characterization and application of DNA and DNA-PEDOT:PSS-based membranes as hole-carrier material (HTM) in dye-sensitized solar cells (DSSC). The UV-Vis analysis of the samples revealed 80% of transparency at 600 nm for the isolated DNA and 62% at 550 nm for DNA-2% PEDOT:PSS. The FTIR analysis of the samples showed characteristic peaks of both the DNA and PEDOT:PSS, confirming its incorporation into membranes. The results of DSC analysis revealed the presence of Tg at -67ºC and its disappearance with the addition of PEDOT:PSS to the formulation of HTM. The TGA analysis showed increased stability of the samples with the addition of PEDOT:PSS reaching 200ºC. All samples showed 19% of ashes at 900ºC. The DNA-based membranes were also subjected to ionic conductivity measurements showing the highest value of 3.2x10-4 S/cm2 at room temperature and of 0.1x10-3 S/cm2 at 75ºC for the isolated DNA. Samples of DNA-PEDOT:PSS showed conductivity value of 4.67x10-5 S/cm2 for DNA-2% PEDOT:PSS sample at room temperature which decreased with increasing percentage of PEDOT:PSS. X-ray diffraction revealed an increase of the crystallinity of the samples with the addition of PEDOT:PSS and the highest value found was 77.8% for the sample of DNA-10% PEDOT:PSS. The DSSCs showed a reduction of solar efficiency from 2.04% to 1.49% after the introduction of DNA-based membranes. This phenomenon was explained in terms of increased reflectance and surface roughness of the samples that difficult the transport and recombination of charge carrier species.

Master of Science / Department of Chemistry / Daniel A. Higgins / Lithography techniques have been widely used to fabricate optical, electronic and optoelectronic devices with sub-micron scale spatial resolution. In the most common lithographic procedures, a light sensitive polymer, called a photoresist, is exposed and developed to form a binary relief pattern on a substrate. The finest features are produced by X-ray or electron-beam methods, both of which are very expensive to employ. Less expensive methods use ultraviolet (UV) light to expose the photoresist through a photomask. The resolution in these methods is somewhat lower and is governed by diffraction of light by the photomask, the quality of the photomask, and by any chemical/physical development steps subsequently employed. Due to the above limitations, we have been investigating direct-write, ablative multiphoton lithography as an alternative method for preparing high-resolution patterns. With this method, near-IR light from an ultrafast pulsed laser source is focused into a polymer film, leading to depolymerization and vaporization of the polymer. Arbitrary binary patterns can be produced by raster scanning the sample while controlling exposure of the film to the laser. Importantly, high-resolution etching of the polymer film is achieved without the use of a photomask and without chemical development steps. While arbitrary patters are easily prepared, it is also possible to prepare three-dimensional (i.e. grayscale) surface relief structures. In this study, ablative multiphoton photolithography is used to prepare binary and grayscale structures in thin films of PEDOT:PSS, an electrically conductive organic polymer blend. A simple kinetic model is proposed to explain the etching process. Data on the power-dependence of polymer etching can be fit to this model and is used to determine the order of the nonlinear optical process involved. The etch depth as a function of laser focus is also investigated and shown to follow the same kinetic model. The results show that three-dimensional (grayscale) patterns can be prepared by modulating either the laser power or the laser focus. Images of several binary and grayscale structures prepared by this method are presented.

L'utilisation de matériaux transparents et conducteurs a subi une croissance exponentielle lors de la dernière décennie, puisque faisant partie intégrante de nombreux dispositifs optoélectroniques tels que les écrans tactiles & les cellules solaires. Parmi ces matériaux, l'oxyde d'indium-étain occupe la quasi-totalité du marché puisqu'il associe une conductivité élevée et une transparence supérieure à 90% sous forme de film mince. Cependant, le développement de technologies flexibles pousse à rechercher des alternatives à son utilisation car son cout élevé et sa faible flexibilité le rendent incompatible. Au milieu des alternatives carbonées (graphène et nanotubes), les nanomatériaux métalliques ou les polymères conducteurs se présentent comme des alternatives intéressantes : bas cout et facilité à mettre en forme pour les polymères conducteurs, hautes performances pour les nanofils métalliques. Cette thèse présente la mise en œuvre de ces matériaux alternatifs par la méthode originale d'électrofilage et l'étude de leurs propriétés optoélectroniques. La maitrise des conditions de mise en forme (champ, débit, paramètres environnementaux) et l'optimisation des solutions utilisées (rhéologie, concentration en polymère, co-solvants) nous a permis d'obtenir 2 types de nanostructures : des nanofibres 100% polymériques à base de PEDOT:PSS et des nanofibres composites PVP:Nanofils d'argent. L'étude des propriétés opto-électroniques des réseaux ainsi obtenus a aussi été étudiée / The use of transparent and conductive materials has been growing exponentially in the last decade as they are part of many optoelectronic devices such as touch screens and solar cells. Among these materials, Indium-Tin Oxide (ITO) is the market reference since it combines a low resistivity and a high transparency up to 90% in the form of thin film. However, the growing in the development of flexible technologies created a real need in alternatives as ITO has poor mechanical properties. Carbon nanotubes and graphene are potential substitutes, but metallic nanowires and conductive polymers have been developed for their high performances and low cost respectively.This thesis presents the implementation of these alternatives by the original method of electrospinning and the study of their optoelectronic properties. The optimization of the experimental setup (field, rate, environmental parameters) and solutions (rheology, polymer concentration, co-solvents) allowed us to obtain 2 different kinds of nanostructures: fully polymeric with PEDOT:PSS and composite with PVP and silver nanowires. The study of the optoelectronic properties of the resulting networks has also been investigated

In organischen Leuchtdioden (OLEDs) werden üblicherweise anorganische Materialien wie Indium-Zinn-Oxid (ITO) als transparente leitfähige Anoden verwendet. ITO besitzt allerdings eine geringe Austrittsarbeit und kann deshalb Löcher nicht effizient in organische Materialien injizieren. Weiterhin ist ITO eine Quelle von Indium- und Sauerstoff-Ionen, die in die organischen Materialien diffundieren und dort mit der Organik reagieren bzw. als effiziente Exzitonenvernichter agieren. Eine mögliche Alternative zu ITO sind hoch leitfähige Polymere wie PEDOT:PSS und Polyaniline. Diese Studie untersucht die physikalischen Aspekte von OLEDs mit elektrisch dotierten Ladungstransportschichten auf Polymeranoden. Hierbei werden pin-OLEDs auf ITO mit OLEDs auf Polymeranoden direkt verglichen und mit dem derzeitigen Stand der Technik diskutiert. Die Untersuchungen zeigen, daß OLEDs auf PEDOT:PSS Anoden eine höhere Effizienz erreichen als OLEDs auf ITO Anoden. Um die physikalischen Unterschiede von pin-OLEDs auf ITO und PEDOT:PSS Anoden zu untersuchen, werden optische Simulationen sowie Ultraviolett-Photoemissions-Spektroskopie (UPS) und Lebensdauermessungen durchgeführt. Die optischen Simulationen zeigen, daß die Polymeranoden durch ihren geringen Brechungsindex eine höhere Lichtauskopplungseffizienz besitzen als OLEDs mit einer ITO-Anode. Außerdem finden UPS-Messungen eine geringere Löcherinjektionsbarriere von PEDOT:PSS zu dotierten und undotierten Lochtransportschichten. Aus diesem Grund ist die Ladungsträgerinjektion an der Anoden-Organik-Grenzfläche effizienter, wenn eine PEDOT:PSS-Anode verwendet wird. Lebensdauermessungen von pin-OLEDs auf PEDOT:PSS-Anoden zeigen eine vergleichbare Lebensdauer zu OLEDs auf ITO-Anoden. Die Ergebnisse dieser Untersuchungen zeigen eindeutig, daß Polymeranoden das Potential besitzen, ITO als Anode zu ersetzen und zusätzlich die OLED-Effizienz zu erhöhen.

As aplicações dos dispositivos conversores de energia luminosa, principalmente da luz solar, em energia elétrica são muito variadas e com freqüência surge a possibilidade de uma nova aplicação. Muito tem sido discutido sobre aplicações de células solares em vestimentas, mochilas, tetos de estacionamentos e em embalagens eletrônicas. Esses tipos de aplicações não exigem dispositivos de alto desempenho, porém exigem que seja de baixo custo de processamento e, principalmente, que sejam flexíveis. Dispositivos fotovoltaicos flexíveis devem então ser fabricados por técnicas simples de processamento para permitir sua eventual produção em massa. Esse trabalho pretende dar uma contribuição na escolha dos materiais a serem usados em dispositivos fotovoltaicos flexíveis, focando seu desenvolvimento em células solares orgânicas de heterojunção de volume (BHJ), que são comumente processadas por solução. A estrutura escolhida foi a convencional de multicamadas onde o anodo transparente é o ITO (óxido de índio-estanho), seguida de uma camada transportadora de buracos (PEDOT:PSS), da camada ativa, e do cátodo, que em nosso caso foi formado por cálcio e alumínio, ambos depositados a vácuo. Como camada ativa, principal elemento de estudo nesse trabalho, foram estudados o P3HT:PC61BM, e o PTB7-Th:PC71BM, como elementos doador de elétrons (polímero) e aceitador de elétrons (derivado de fulereno). Em especial com o dispositivo fabricado com o PTB7-Th:PC71BM foi possível elaborar mudanças de processamento e assim melhorar consideravelmente a sua eficiência de conversão de potência. Em seguida, através de medidas de corrente-tensão (J-V) no escuro e sob iluminação, pudemos analisar a evolução dos parâmetros das células, como as resistências série (Rs) e paralelo (Rp), e também aqueles que definem a qualidade da célula solar: a corrente de curto-circuito (Jsc), a tensão de circuito aberto (Voc), o fator de preenchimento (FF), e a eficiência (η). Através dos ajustes das curvas J-V, no escuro e sob iluminação, usando expressões de J(V) extraídas de circuitos equivalentes, respectivamente, dos diodos e das células solares, pudemos realizar uma análise mais efetiva de como as resistências série e paralelo mudam com os elementos da camada ativa e também com diferentes processamentos. O fator de preenchimento (FF) é outro parâmetro importante que determina a eficiência de conversão de energia de uma célula solar orgânica, e existem vários fatores que podem influenciar significativamente o seu valor. Essa é uma das razões do porquê é difícil identificar a real origem desse parâmetro. Essa tese também deu elementos que correlacionam a estrutura química e morfológica da camada ativa com o fator de preenchimento. / The applications of light energy converters, especially the sunlight, in electrical energy are very varied and there is often the possibility of the appearance of new applications. Much has been discussed about solar cell applications in clothing, backpacks, parking ceilings and in electronic packaging. These types of applications do not require high-performance devices, but they do require low-cost processing and, above all, that they are flexible. Flexible photovoltaic devices must then be manufactured by simple processing techniques to allow their eventual mass production. This work intends to contribute to the choice of materials to be used in flexible photovoltaic devices, focusing their development on organic bulk heterojunction solar cells (BHJ), which are commonly processed via solution. The structure chosen for the device was the multilayer one, where the transparent anode is the ITO (indium- tin oxide), followed by a hole transport layer (PEDOT:PSS), the active layer, and the cathode, which in our case was formed by calcium and aluminum, both deposited under vacuum. As active layer, the main element of study in this work, we studied the P3HT: PC61BM and the PTB7-Th: PC71BM, as electron donor (polymer) and electron acceptor elements (derived from fullerene). In particular with the device made with the PTB7-Th:PC71BM it was possible to changes processing parameters and thus enhancing its power conversion efficiency. Then, through current-voltage measurements (J-V), in the dark and under illumination, we were able to analyze the evolution of the cell parameters, such as the series (Rs) and shunt (Rp) resistances, as well as those that define the solar cell quality: short-circuit current (Jsc), open-circuit voltage (Voc), fill factor (FF), and efficiency (η). Through the adjustments of the J-V curves, in the dark and under illumination, using J(V) expressions, for equivalent circuits of the diodes and solar cells respectively, we were able to perform a more effective analysis of how the series and shunt resistances change with the elements of the active layer and also with its processing. Fill factor (FF) is another important parameter that determines the energy conversion efficiency of an organic solar cell, and there are several factors that can significantly influence its value. This is one of the reasons why it is difficult to identify the true source of this parameter. This thesis also gave elements that correlate the chemical and morphological structure of the active layer with the fill factor.

Στην παρούσα εργασία μελετήθηκε η θερμική γήρανση του poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS), με μετρήσεις ειδικής αγωγιμότητας συνεχούς ρεύματος, φασματοσκοπίας φωτοηλεκτρονίων και ηλεκτρονίων Auger από ακτίνες-Χ (XPS και ΧΑΕS) και φασματοσκοπίας φωτο-ηλεκτρονίων από υπεριώδη ακτινοβολία (UPS). Για τη μελέτη αυτή χρησιμοποιήθηκαν δείγματα PET (Polyethylene terephthalate) PEDOT:PSS, υπό μορφή λεπτών υμενίων (films), πάχους επίστρωσης 50 nm και 180 nm. Οι θερμοκρασίες στις οποίες καταπονήθηκαν τα δείγματα ήταν οι 120οC, 150οC και 170οC, ενώ οι χρόνοι καταπόνησης κυμάνθηκαν από 0 έως 100 ώρες περίπου. Για την επεξεργασία των μετρήσεων θερμικής γήρανσης, χρησιμοποιήθηκε το μοντέλο Variable Range Hopping (VRH) του Mott που προβλέπει μια εξάρτηση της σ(Τ) της μορφής: (VRH) Στη σχέση αυτή σ είναι η ειδική ηλεκτρική αγωγιμότητα, Τ η θερμοκρασία, σο, Το σταθερές που εξαρτώνται από το υλικό και α εκθέτης που σχετίζεται με τον αριθμό των διαστάσεων που πραγματοποιείται η μετάβαση με άλματα ενός φορέα ηλεκτρικού φορτίου στις αλυσίδες του PEDOT. Τα αποτελέσματα αυτών των μετρήσεων έδειξαν ότι η θερμική ταλαιπωρία, οδηγεί στη θερμική γήρανση των δειγμάτων, με ταχύτερο ρυθμό στα λεπτότερα υμένια των 50 nm, καταδεικνύοντας ότι το πάχος επίστρωσης αποτελεί σημαντικό παράγοντα στην επιβράδυνση της γήρανσης. Οι φασματοσκοπικές μετρήσεις έδειξαν ότι η θερμική καταπόνηση οδηγεί στην μείωση του ποσοστού PSS στην επιφάνεια του δείγματος. Επίσης βρέθηκε ότι μειώνεται η τιμή του έργου εξόδου. Στην συνέχεια εξετάσθηκε η επίδραση παραγόντων, όπως ο χρόνος και ρυθμός θέρμανσης, καθώς και η περιβάλλουσα ατμόσφαιρα στην ηλεκτρική αγωγιμότητα. Παρατηρήθηκε ότι σε όλες τις περιπτώσεις κοντά στους 400 Κ σημειώνεται μετάβαση μονωτή-μετάλλου (Insulator-Metal Transition, IMT). Διαπιστώθηκε ότι το σημείο μετάβασης εξαρτάται σημαντικά από τις αλλαγές που προκαλούνται στη δομή των υμενίων. Από τις καμπύλες που προέκυψαν μετά από σταθερή θέρμανση δειγμάτων πάχους 120 nm, σε θερμοκρασίες από 100 oC έως 190 οC, παρατηρήθηκε ότι ανάλογα το χρόνο και τη θερμοκρασία καταπόνησης, είναι δυνατόν να σημειωθεί άλλοτε υποβάθμιση και άλλοτε βελτίωση της αγωγιμότητας. Τα φαινόμενα αυτά αποδόθηκαν στη δράση δύο ανταγωνιστικών μηχανισμών. Τέλος, η σύγκριση αποτελεσμάτων θερμικής καταπόνησης σε ατμοσφαιρικές συνθήκες και σε αδρανή ατμόσφαιρα He, έδειξε ότι η θερμική γήρανση ήταν πιο έντονη στην περίπτωση δειγμάτων που καταπονήθηκαν στον ατμοσφαιρικό αέρα, οφειλόμενη στις μη αντιστρεπτές δομικές αλλαγές που επιφέρει η οξείδωση παρουσία του οξυγόνου στις αλυσίδες του PEDOT. Αντίθετα, σε αδρανή ατμόσφαιρα Ηe οι ηλεκτρικές ιδιότητες βελτιώνονται σημαντικά με τη θέρμανση. / In this work the thermal aging of the copolymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) has been investigated by measuring the d.c. conductivity σ and photoelectron spectroscopy data (XPS, XAES, UPS). For this study thin films of PET PEDOT:PSS of 50 and 180 nm of thickness were used. The temperatures of the thermal treatment were 120 0C, 150 0C and 170 0C and the times of this process varied between 0 and 100 hours approximately. For the d.c. conductivity data, the Mott’s variable range hopping model was used, described by the following relation: (VRH) where T is the absolute temperature, σ0, T0 parameters depending on the material and α an exponent, which is related to the number of dimensions of the transport by hopping of a carrier in and between the PEDOT chains. These measurements showed that the thermal treatment has as a result the aging of the samples, which was more intense for the 50 nm films, proving that the increase of the samples thickness reduces significantly the thermal aging. The spectroscopic measurements showed that the thermal treatment leads to the removal the PSS percentage on the surface of the specimen. It was found also, that the value of the work function of the samples decreases with aging. Finally, the effect of the stability of d.c. conductivity value during prolonged heating at constant temperature, as well as the rate of the thermal treatment and the composition of the surrounding atmosphere on the electrical conductivity were investigated. It was found that in all cases, an insulator – metal transition (IMT) was taking place near the temperature of 400 K. The exact temperature of this transition depends on the changes taking place in the structure of the films. From the experimental curves after heating the 120 nm samples with constant rate for temperatures between 100 0C and 190 0C, it was found that it is possible to have either, deterioration or improvement of the conductivity. These phenomena were attributed to two different competitive mechanisms. Finally, the comparison of the results of the thermal treatment under atmospheric conditions and under inert atmosphere of He, showed that thermal aging is more intense in the first case, due to irreversible structural changes brought about by oxidization in the presence of moisture and oxygen in the PEDOT chains. On the other hand, it was found that the electrical properties were improved significantly by heating under the inert atmosphere of He.

This thesis studies the degradation of perovskite photovoltaic cells placed in atmospheres of different moisture. Samples with inverse structure: ITO/ PEDOT:PSS/ CH3NH3PbI3–XClX / PC70BM/ Ca/ Al were prepared. Electrical characteristics were measured for 2 months and similar degradation trend was observed for all the samples. Perovskite cell efficiency PCE decreased to 20 % of the initial value in t80= 46±3 days in laboratory, t80=23±1$ days in nitrogen atmosphere and t80=25,7±0,6 dní days in dry atmosphere. For the initial 27 days of the experiment, a faster degradation linked with the decrease of ISC, FF and VOC was observed. After this period, the value of FF has stabilised at 0,777±0,009 % and the value of VOC at 0,70±0,02 % of their original value (in the laboratory atmosphere). Additional fall of PCE resulted only from the decrease of ISC and was slower than in the initial period. From the results acquired, it has emerged that during the experiment, the cell encapsulation provided a sufficient barrier against outer moisture. Residual moisture present in the sctructure, was labeled as the source of the degradation. The moisture is believed to enter with the hygroscopic material PEDOT:PSS during the samples preparation procedure. During the degradation, absorption measurements of photovoltaic cells were executed. The absorption spectra didn't change. That indicates, that the decrease of ISC is not caused by the reduction of light absorption. The thesis also studied the degradation of perovskite solar cells under illumination. The samples were exposed to UV radiation for 55,5 hours. The PCE time of decrease to 20 % of the initial value was t80 = 6±2 days. It was revealed, that UV radiation significantly accelerates the decrease of ISC.

During the last 30 years a new research and technology field of organic electronic materials has grown thanks to a groundbreaking discovery made during the late 70’s. This new field is today a worldwide research effort focusing on exploring this new class of materials that also enable many new areas of electronics applications. In the organic electronics research field conducting organic molecules and polymers are synthesized and used in devices. The reason behind the success of conducting polymers is the flexibility to develop materials with new functionalities via clever chemical design and the possibility to use low-cost production techniques to manufacture devices. This thesis reviews and describes different aspects of the organic electronics, here focusing on electrochromic displays; device improvements, the study of degradation and also patterning technology for rational manufacturing processing. The color contrast in electrochromic displays based on conjugated polymers was increased with approximately a factor of two by adding an extra electrochromic polymer. It was found that electrochemical over-oxidation (ECO) limits the flexibility in choosing desired electrochromic materials. ECO is one of the main degradation mechanisms in electrochromic displays. ECO is an efficient and fast process to permanently reduce the electronic conductivity in polythiophenes. From this, a novel patterning process was developed, in which the films of polythiophenes can be patterned through local and controlled deactivation of the conductivity. The ECO has been combined with different patterning tools to enable the use of existing printing tools for manufacturing. In combination with screen-printing, low-cost and high volume roll-to-roll patterning was demonstrated, while together with photolithography, patterning down to 2 µm can be achieved. Systematic studies have shown that conductivity contrasts beyond 107 can be achieved, which is enough for various simple electronic systems. To generate better understanding of the ECO phenomena the effect of pH on the over-oxidation characteristics was studied. The results suggest that a part of the mechanism for over-oxidation depends on the OH– concentration of the electrolyte used.

Organic solar cells have been showing promise as a way of producing renewableenergy with the help of light, flexible, and production effective materials.The efficiencies and lifetimes reached in organic solar cells have steadily beenincreasing over the years as more research in the field is being conducted.One way of increasing the efficiency in organic solar cell devices is introducingan interlayer between the photoactive material and the anode, referred toas the ’hole transport layer’. Most commonly used as a hole transport layer isthe material PEDOT:PSS, which offers desired properties such as transparency,simple processing and good ohmic contact between anode and photoactive material.PEDOT:PSS is also known to be a degradation site in organic solar cells,as it will corrode the electrode in the presence of water.This project has consisted of investigating PEDOT:PSS along with two othercandidates that may one day come to replace PEDOT:PSS as the most commonlyused material, molybdenum trioxide (MoO3) and phosphomolybdic acid(PMA). The aim was to investigate how the different materials energy bandstructure would be affected upon exposure to sunlight, air and annealing, byobserving the work function under different conditions.