Organic photovoltaic (OPV) devices are emerging as a reliable source of energy due to their combination of unique features. Though desired for their flexibility, low cost, light weight, large area fabrication compatibility and eco-friendly nature, these devices face numerous challenges in achieving high performance and stability. The organic-electrode interface specifically plays a key role in controlling device stability. Recent studies have revealed that the stability is heavily affected by the adhesion of the organic-electrode interface. Measurement of adhesion at these interfaces, however, is a challenging task. In this study, Normal Force Adhesion testing was assessed to determine its suitability for organic devices. In this approach, force is applied perpendicular to the substrate, over the entire surface area of one device (9 mm2) until delamination occurs. In addition to the extracted force-distance curves, images of the interfaces before and after each experiment and a real-time, in-situ video taken from a lateral perspective were examined. All three of these critical pieces of information are necessary to obtain a complete picture of the success of a Normal test. A statistical assessment has been made of the testing apparatus, using many samples (> 50) of one metal - organic combination, Al-Alq3 - an archetypal combination for organic electronics. In addition, five other metal-organic combinations widely used in organic electronic devices, have been chosen to assess the Normal force approach. Due to the ease of testing a large number of samples, Normal force testing does appear to be a viable approach to examining interfacial adhesion, though care must be taken in the experimental design to avoid common experimental failures. Based on the results, a few recommendations have been made to improve the utility of the adhesion testing system for rapid quality testing of organic devices. / Thesis / Master of Applied Science (MASc)

Les matériaux conducteurs transparents font partie intégrante de très nombreux dispositifs optoélectroniques (de type cellule solaire, OLED, capteur tactile, etc.). Pour des raisons techniques et économiques (évolution des marchés vers les applications flexibles),d’importantes recherches sont mises en œuvre pour remplacer les couches minces d’oxydes métalliques (principalement en ITO) actuellement utilisées. En effet, de par sa faible résistance mécanique à la flexion et son coût d’élaboration élevé, l’ITO ne répond pas aux besoins de ces marchés émergents. L’utilisation de nanomatériaux en solution, et en particulier de nanofils métalliques, apparaît comme une alternative très prometteuse qui offre la possibilité d’utiliser des méthodes d’impression bas coût et grande surface. Ces travaux de thèse présentent les procédés de synthèse et purification de nanofils d’argent et de cuivre à forme facteur de forme. L’impression par spray de réseaux 2D percolants permet la réalisation d’électrodes flexibles démontrant d’excellentes propriétés optoélectroniques.Les nanofils d’Ag semblent toutefois être de meilleurs candidats que les nanofils de Cu (synthèse multi-grammes, impression grande surface, meilleure stabilité à l’air, etc.). Ainsi,après avoir identifié les principaux verrous technologiques ayant trait à l’utilisation des AgNF (rugosité, adhésion, travail de sortie, stabilités environnementales/électriques), différentes solutions ont été proposées dans le but d’améliorer les performances et de rendre les nanofils d’argent compatibles avec l’intégration en dispositif. Le potentiel des nanofils d’argent en tant que remplaçants de l’ITO a été confirmé grâce à l’intégration d’électrodes dans divers dispositifs fonctionnels (cellule solaire organique, capteur capacitif ou encore film chauffant). / Transparent conductive thin films are widely used in technologies like solar cells, light-emitting diodes, and display technologies. The fabrication of transparent conductive films is currently realized with thin films of transparent conductive oxides (TCOs), and in particular indium tin oxide (ITO). The as-made ITO transparent conductors suffer from limitations like costly fabrication process and brittleness. The use of solution-processable nanomaterials, and especially metallic nanowires, appears as a promising alternative since it affords a large area, low-cost deposition method with high performances.This thesis report that by optimizing synthesis methods and printing methods, flexible electrodes demonstrating excellent opto-electronic properties were performed, either with the use of a percolating network of silver nanowires or copper nanowires. The silver nanowires, however, seem to be better candidates than the copper nanowires (synthesized substantial amount, printing large area, better stability in air, etc.). Thus, having identified the main technological barriers related to the use of Ag NW (roughness, adhesion, work function, electrical/environmental stabilities), different solutions have been proposed in order to make the silver nanowires compatible with as many devices for integration.The potential of silver nanowires as replacements for ITO was confirmed through the integration of electrodes in various functional devices (organic solar cell, capacitive touch sensor or the film heater).

<p dir="ltr">Conjugated polymers are organic macromolecules that are characterized by a backbone chain of alternating double- and single-bonds. This alternating pattern results in delocalized π electronic systems, contributing to electronic conduction. In the solid state, conjugated polymers exhibit weak intermolecular interactions, rendering them soft nature in comparison to many of their inorganic counterparts, such as silicon, which consist of ‘hard' three-dimensional networks of rigid covalent bonds. In electrolyte, this weak intermolecular interaction creates free pathways for ion penetration and facilitates mixed ionic-electronic coupling. The ionic-electronic coupling of conjugated polymers impacts nearly all their properties, including light absorption, electronic conductivity, mechanical strength, etc.</p><p dir="ltr">Organic iono-optoelectronics represent a class of devices where the ionic-electronic coupling in conjugated polymers can be synergistically or independently controlled by light irradiation and electrical voltage, enabling multimode electronic and optical functionalities. This dissertation explores two types of organic iono-optoelectronic devices: electrochromic devices and artificial eyes. In electrochromic devices, the ionic-electronic coupling is dynamically modulated by electrical voltage, which induces optical changes of conjugated polymers for applications in information visualization, thermal management, camouflage, etc. Conversely, artificial eyes utilize optical stimulation to tailor the electronic-ionic coupling, with electrical potential changes serving as readout. This paradigm shift opens the door to the development of light-driven biomedical electronics and intelligent visual systems. In the development of electrochromic devices, we introduce two strategies that expand the color palette and enhance the optical control of electrochromic devices, promoting their potential use in display and camouflage. In the development of artificial eye development, we introduce an electrochemical transistor device with integrated functions of light perception, memorization, and recognition by leveraging photon-modulated ion-electronic coupling. This device demonstrates great potential for intelligent visual systems and promises future optoelectronic neural interfaces.</p>