Dissertations / Theses on the topic 'Ternary Blend Organic Solar Cells'

L’objectif final de la thèse est l'impression de la couche photo-active ternaire d'une cellule solaire organique en utilisant deux approches: l'une concerne l'apport de nanotubes de carbone (SWCNT) pour améliorer les propriétés de transport, l'autre concerne la préparation de mélanges ternaires de matériaux pour contrôler la couleur des cellules. Les encres pour la couche active incluant des SWCNT fonctionnalisés sont composées d’un donneur d'électron (polymère) (poly(3-hexylthiophène), [P3HT]) et d’un accepteur d'électron ( [6,6]-phényl C61-butyrique ester méthylique d'acide [PCBM]) et ont été développées pour la fabrication de cellules inversées. Ces cellules sont réalisées sur substrats de verre pour l'optimisation de leurs performances, puis sur substrats plastiques pour les applications. Diverses couches d'interfaces ont été testées, qui incluent l'oxyde de zinc (ZnO, couches obtenues par pulvérisation ionique (IBS) ou à partir de solutions de nanoparticules) pour la couche de transport d'électrons et le PEDOT:PSS, le P3MEET, le V2O5 et le MoO3 pour la couche de transport de trous. Des essais ont été effectués avec et sans CNT afin d’étudier leur impact sur les performances. Des résultats similaires sont obtenus dans les deux cas. Il était attendu que les CNT améliorent les performances, ce qui n’a pas été observé pour le moment. Des travaux supplémentaires sont donc nécessaires au niveau de la formulation de la couche active.Avec trois polymères de couleur rouge (P3HT), bleu (B1) et vert (G1), nous avons préparé des mélanges ternaires efficaces permettant l'obtention de couleurs jusque là indisponibles . Nous avons fait une étude sur le piégeage et les mécanismes de diodes parallèles associés aux mélanges. En général, nous avons constaté que les mélanges ternaires de polymères bleu et vert peuvent être décrits par une mécanisme de diodes parallèles, sans entrainer de perte de performances, ce qui n'est pas possible pour les systèmes P3HT:B1 :PCBM et P3HT:G1:PCBM qui se piègent mutuellement. L’objectif final du projet est l'impression de la couche photo-active ternaire d'une cellule solaire organique, composites ternaires (polymère:polymères:acceptor) ou dopés avec les SWCNT. Cette étape nécessite encore des développements futurs
Two approaches were followed to achieve increased control over properties of the photo-active layer (PAL) in solution processed polymer solar cells. This was accomplished by either (1) the addition of functionalized single-walled carbon nanotubes (SWCNTs) to improve the charge transport properties of the device or (2) the realization of dual donor polymer ternary blends to achieve colour-tuned devices.In the first component of the study, P3HT:PC61BM blends were doped with SWCNTs with the ambition to improve the morphology and charge transport within the PAL. The SWCNTs were functionalized with alkyl chains to increase their dispersive properties in solution, increase their interaction with the P3HT polymer matrix, and to disrupt the metallic characteristic of the tubes, which ensures that the incorporated SWCNTs are primarily semi-conducting. P3HT:PCBM:CNT composite films were characterized and prepared for use as the photoactive layer within the inverted solar cell. The CNT doping acts to increase order within the active layer and improve the active layer’s charge transport properties (conductivity) as well as showed some promise to increase the stability of the device. The goal is that improved charge transport will allow high level PSC performance as the active layer thickness and area is increased, which is an important consideration for large-area inkjet printing. The use of ternary blends (two donor polymers with a fullerene acceptor) in bulk-heterojunction (BHJ) photovoltaic devices was investigated as a future means to colour-tune ink-jet printed PSCs. The study involved the blending of two of the three chosen donor polymers [red (P3HT), blue (B1), and green (G1)] with PC61BM. Through EQE measurements, it was shown that even devices with blends exhibiting poor efficiencies, caused by traps, both polymers contributed to the PV effect. However, traps were avoided to create a parallel-like BHJ when two polymers were chosen with suitable physical compatibility (harmonious solid state mixing), and appropriate HOMO-HOMO energy band alignment. The parallel diode model was used to describe the PV circuit of devices with the B1:G1:PC61BM ternary blend

Polymer photovoltaic systems whose photoactive layer is a blend of a semiconducting polymer with a fullerene derivative in a bulk heterojunction configuration are amongst the most successful organic photovoltaic devices nowadays. The three-dimensional organization in these layers (the morphology) plays a crucial role in the performance of the devices. Detailed characterization of this organization at the nanoscale would provide valuable information for improving future material and architectural design and for device optimization. In this thesis, the results of morphology studies of blends of several polyfluorene copolymers (APFOs) blended with a fullerene derivative are presented. Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy was combined with dynamic Secondary Ion Mass Spectrometry (dSIMS) for surface and in-depth characterization of the blend films. NEXAFS was performed using two different electron detection methods, partial (PEY) and total (TEY) electron yield, which provide information from different depth regimes. Quantitative compositional information was obtained by fitting the spectra of the blend films with a linear combination of the spectra of films of the pure components. In blends of APFO3 with PCBM in two different blend ratios (1:1 and 1:4 of polymer:fullerene) NEXAFS data show the existence of compositional gradients in the vertical direction for both blend ratios, with clear polymer enrichment of the free surface. A series of APFOs with systematic changes in the side-chains was studied and it was shown that those small modifications can affect polymer:fullerene interaction and induce vertical phase separation. Polymer-enrichment of the free surface was clearly identified, in accordance with surface energy minimization mechanisms, and a compositional gradient was revealed already in the first few nanometers of the surface of the blend films. dSIMS showed that this vertical phase separation propagates throughout the film. It was possible to determine that as the polar character of the polymer increases, and thus the polymer:fullerene miscibility is improved, the tendency for vertical phase separation becomes stronger.

Paper II was not published at the time of the licentiate defence and had the title: NEXAFS spectroscopy study of the surface composition in APFO3:PCBM blend films

L’énergie solaire photovoltaïque organique (OPV) est une technologie émergente exempte de matériaux rares et à faibles coûts énergétiques de production. Ces modules, composés de plusieurs couches minces empilées, peuvent être souples, semi-transparents et de différentes formes et couleurs, permettant de les intégrer dans le paysage urbain ou aux objets du quotidien. A l’échelle laboratoire, les rendements de conversion énergétique reportés en OPV n’ont cessé de croitre d’année en année, grâce en particulier à l’émergence de nouvelles couches actives, classiquement composées de deux semi-conducteurs organiques, l’un donneur d’électrons, l’autre accepteur d’électrons (système binaire). Il a été montré qu’il est possible d’en ajouter un troisième pour former un mélange ternaire afin d’améliorer les performances tout en gardant les mêmes coûts de production. Le but de cette thèse est donc de comprendre l’impact du troisième composé et de développer des solutions innovantes tout en intégrant les contraintes liées à leur industrialisation. Dans un premier temps, des couches binaires à base des polymères DT-PDPP2T-TT et PTQ10 ont été mises au point en respectant ces contraintes. Leurs performances prometteuses ont servi de socle à l’étude des mélanges ternaires. Le premier raisonnement s’est basé sur l’augmentation de la densité de courant de court-circuit en ajoutant un composé présentant un spectre d’absorption solaire complémentaire. Cette démarche n’a pas été concluante car le facteur de forme diminuait fortement. Il a alors été décidé de se concentrer sur ce paramètre en ajoutant du PC61BM, accepteur à forte mobilité d’électrons. Cette stratégie a permis de porter les rendements de conversion jusqu’à 10.3% en conditions semi-industrielles avec un solvant non toxique et jusqu’à 14.7% avec un solvant halogéné. Cette amélioration a été attribuée à des changements morphologiques impactant le transport de charge. De plus, lorsque les accepteurs sont miscibles, la tension en circuit ouvert est proportionnelle au ratio entre les deux accepteurs. Une approche prédictive basée sur les énergies de surface a ensuite été menée pour mesurer la compatibilité des matériaux entre eux. Les dispositifs ternaires à base de PTQ10 : 4TIC-4F : PC61BM ont montré une meilleure photostabilité. Pour finir, une étude de pré-industrialisation s’est avérée concluante en vue d’essais à plus grande échelle
Organic photovoltaics (OPV) is a promising solar energy technology excluding the usage of rare elements and with low production costs. These multilayer OPV modules can be flexible, semi-transparent and with various colors enabling innovative usage in the urban landscape and on our everyday technological items. At lab scale, over the years, the power conversion efficiency of OPV cells grew up dramatically, especially thanks to the development of novel active layers, blends of two organic semiconductors, one electron donor and one electron acceptor (binary system). Recently, it has been shown that adding a third material in the active layer, forming a ternary blend, increases the performances. This strategy is of interest for the OPV industry by maintaining the low production costs of the modules. Therefore, this work aims to understand the role of this third component and to develop innovative active layers while respecting the industrial requirements for large-scale production. First, we focused on binary blends with PTQ10 and DT-PPDT2T-TT as polymeric donors. Promising efficiencies were achieved on these binary systems as a base for our ternary studies. We tried to increase the short circuit current by adding a third organic semiconductor with complementary light absorption. This approach was not successful because the fill factor dropped drastically. Thus, we focused on improving this parameter by adding the well-known fullerene acceptor PC61BM. This strategy enabled to increase the efficiency up to 10.3% in semi-industrial conditions with a non-toxic solvent and up to 14.7% in halogenated solvent. Morphological changes were responsible of charge transport improvement, which has proven to be one of the key factor in ternary blends. In addition, the open circuit voltage has been shown proportional to the weight ratio between both acceptors when they form an alloy. Based on these studies, we developed a predictive approach to assess the compatibility between the materials. Finally, ternary PTQ10:4TIC-4F:PC61BM devices turned out to be the most promising in terms of pre-industrialization and photostability

This study focuses on the architectural modification of pin-type small-molecule organic solar cells, in particular on the absorption layer and its influence on the key solar cell parameters, such as short circuit current density, fill factor and open circuit voltage. Three different approaches have been applied to improve the match between the solar spectrum and the spectral sensitivity of organic solar cells. In the first part, deposition parameters such as substrate temperature, gradient strength and (graded) absorption layer thickness are evaluated and compared to organic solar cells with homogeneously deposited absorption layers. Moreover, the gradient-like distribution of the absorption layer is characterized optically and morphological effects have been extensively studied. In order to isolate the origin of the efficiency improvement due to the graded architecture, voltage-dependent spectral response measurements have been performed and gave new insights. The second part concentrates on the efficient in-coupling of converted UV light, which is usually lost because of the cut off properties of organic light in-coupling layers. Via Förster resonance energy transfer, the absorbed UV light is re-emitted as red light and contributes significantly to higher short circuit current densities. The correlation between doping concentration, simple stack architecture modifications and the performance improvement is duly presented. In the third and last part, the impact of tri-component bulk heterojunction absorption layers is investigated, as these have potential to broaden the sensitivity spectrum of organic solar cells without chemical modification of designated absorber molecules. Along with the possibility to easily increase the photocurrent, an interesting behavior of the open circuit voltage has been observed. Knowledge about the impact of slight modifications within the solar stack architecture is important in order to be able to improve the device efficiency for the production of cheap and clean energy.

In the last 25 years, organic or "plastic" solar cells have gained commercial interest as a light-weight, flexible, colorful, and potentially low-cost technology for direct solar energy conversion into electrical power. Currently, organic solar cells with a maximum power conversion effciency (PCE) of 12% can compete with classical silicon technology under certain conditions. In particular, a variety of strongly absorbing organic molecules is available, enabling custom-built organic solar cells for versatile applications. In order to improve the PCE, the charge carrier mobility in organic thin films must be improved. The transport characterization of the relevant materials is usually done in neat layers for simplicity. However, the active layer of highly efficient organic solar cells comprises a bulk heterojunction (BHJ) of a donor and an acceptor component necessary for effective charge carrier generation from photo-generated excitons. In the literature, the transport properties of such blend layers are hardly studied. In this work, the transport properties of typical BHJ layers are investigated using space-charge limited currents (SCLC), conductivity, impedance spectroscopy (IS), and thermally stimulated currents (TSC) in order to model the transport with numerical drift-diffusion simulations. Firstly, the influence of an exponential density of trap states on the thickness dependence of SCLCs in devices with Ohmic injection contacts is investigated by simulations. Then, the results are applied to SCLC and conductivity measurements of electron- and hole-only devices of ZnPc:C60 at different mixing ratios. Particularly, the field and charge carrier density dependence of the mobility is evaluated, suggesting that the hole transport is dominated by exponential tail states acting as trapping sites. For comparison, transport in DCV5T-Me33:C60, which shows better PCEs in solar cells, is shown not to be dominated by traps. Furthermore, a temperature-dependent IS analysis of weakly p-doped ZnPc:C60 (1:1) blend reveals the energy-resolved distribution of occupied states, containing a Gaussian trap state as well as exponential tail states. The obtained results can be considered a basis for the characterization of trap states in organic solar cells. Moreover, the precise knowledge of the transport-relevant trap states is shown to facilitate modeling of complete devices, constituting a basis for predictive simulations of optimized device structures
Organische oder "Plastik"-Solarzellen haben in den letzten 25 Jahren eine rasante Entwicklung durchlaufen. Kommerziell sind sie vor allem wegen ihres geringen Gewichts, Biegsamkeit, Farbigkeit und potentiell geringen Herstellungskosten interessant, was zukünftig auf spezielle Anwendungen zugeschnittene Solarzellen ermöglichen wird. Die Leistungseffzienz von 12% ist dabei unter günstigen Bedingungen bereits mit klassischer Siliziumtechnologie konkurrenzfähig. Um die Effzienz weiter zu steigern und damit die Wirtschaftlichkeit zu erhöhen, muss vor allem die Ladungsträgerbeweglichkeit verbessert werden. In organischen Solarzellen werden typischerweise Donator-Akzeptor-Mischschichten verwendet, die für die effziente Generation freier Ladungsträger aus photo-induzierten Exzitonen verantwortlich sind. Obwohl solche Mischschichten typisch für organische Solarzellen sind, werden Transportuntersuchungen der relevanten Materialien der Einfachheit halber meist in ungemischten Schichten durchgeführt. In der vorliegenden Arbeit wird der Ladungstransport in Donator-Akzeptor-Mischschichten mithilfe raumladungsbegrenzter Ströme (space-charge limited currents, SCLCs), Leitfähigkeit, Impedanzspektroskopie (IS) und thermisch-generierter Ströme (thermally stimulated currents, TSC) untersucht und mit numerischen Drift-Diffusions-Simulationen modelliert. Zunächst wird mittels Simulation der Einfluss exponentiell verteilter Fallenzustände auf das schichtdickenabhängige SCLC-Verhalten unipolarer Bauelemente mit Ohmschen Kontakten untersucht. Die Erkenntnisse werden dann auf Elektronen- und Lochtransport in ZnPc:C60-Mischschichten mit verschiedenen Mischverhältnissen angewendet. Dabei wird die Beweglichkeit als Funktion von elektrischem Feld und Ladungsträgerdichte dargestellt, um SCLC- und Leitfähigkeitsmessungen zu erklären, was mit einer exponentiellen Fallenverteilung gelingt. Zum Vergleich werden dieselben Untersuchungen in DCV2-5T-Me33:C60, dem effizientesten der bekannten Solarzellenmaterialien dieser Art, wiederholt, ohne Anzeichen für fallendominierten Transport. Des weiteren werden erstmals schwach p-dotierte ZnPc:C60-Mischschichten mit temperaturabhängiger IS untersucht, um direkt die Dichte besetzter Lochfallenzustände zu bestimmen. Dabei werden wiederum exponentielle Fallenzustände sowie eine Gaußförmige Falle beobachtet. Insgesamt tragen die über Fallenzustände in Mischschichten gewonnenen Erkenntnisse zum Verständnis von Transportprozessen bei und bilden damit eine Grundlage für die systematische Identifizierung von Fallenzuständen in Solarzellen. Außerdem wird gezeigt, dass die genaue Beschreibung der transportrelevanten Fallenzustände die Modellierung von Bauelementen ermöglicht, auf deren Grundlage zukünftig optimierte Probenstrukturen vorhergesagt werden können

This work deals with the investigation and research on organic solar cells. In the first part of this work we focus on the spectroscopical and electrical characterization of the acceptor molecule and fullerene derivative C70. In combination with the donor molecule zinc-phthalocyanines (ZnPc) we investigate C70 in flat and bulk heterojunction solar cells and compare the results with C60 as acceptor. The stronger and spectral broader thin film absorption of C70 and thus enhanced contribution to photocurrent as well as the similar electrical properties with respect to C60 result in higher power conversion efficiencies. In the second part, modifications of the blend layer morphology of a C60:ZnPc bulk heterojunction solar cell are considered. Using substrate heating during co-deposition of acceptor and donor, the molecular arrangement is influenced. Due to the additional thermal energy at the substrate the blend layer morphology is improved and optimized for a substrate heating temperature of 110°C. With transmission electron microscopy, molecular phase separation of C60 and ZnPc and the formation of polycrystalline ZnPc domains in a lateral dimension on the order of 50 nm are detected. Mobility measurements show an increased ZnPc hole mobility in the heated blend layer. The improved charge carrier percolation and transport are confirmed by the enhanced performance of such bulk heterojunction solar cells. Furthermore, we show a strong influence of the pre-deposited p-doped hole transport layer on the molecular phase separation. In the third part, we study the dependency of the open circuit voltage on the mixing ratio of C60 and ZnPc in bulk heterojunction solar cells. For the different mixing ratios we determine the ionization potentials of C60 and ZnPc. Over the various C60:ZnPc blends from 1:3 - 6:1, the ionization potentials change linearly, but different from each other and exhibit a correlation to the change in open circuit voltage. Depending on the mixing ratio an intrinsic ZnPc layer adjacent to the blend leads to injection barriers which result in reduced open circuit voltage. We hence determine a voltage loss dependent on ZnPc layer thickness and barrier height
Diese Arbeit beschäftigt sich mit der Untersuchung und Forschung an organischen Solarzellen und gliedert sich in drei Teile. Im ersten Teil wird auf die spektroskopische und elektrische Charakerisierung des Fullerenderivates C70 eingegangen, welches als Akzeptormolekül in Kombination mit dem Donormolekül Zink-Phthalocyanin (ZnPc) in Flach- und Mischschichtheteroübergänge organischer Solarzellen Anwendung findet. Dabei wird das Molekül mit dem bisherigen Standard Akzeptormolekül C60 verglichen. Die deutlich stärkere und spektral verbreiterte Dünnschichtabsorption von C70, sowie die vergleichbaren elektrischen Eigenschaften zu C60 führen zu einer Effizienzsteigerung in den Flach- und Mischschichtsolarzellen, welche maßgeblich durch die Erhöhung des Kurzschlussstromes erreicht wird. Im zweiten Teil widmet sich diese Arbeit der Morphologiemodifizierung des Mischschichtsystems C60:ZnPc, welche durch Heizen des Substrates während der Mischverdampfung von Akzeptor- und Donormolekülen in organischen Mischschichtsolarzellen erreicht werden kann. Es wird gezeigt, dass mit der zusätzlichen Zufuhr thermischer Energie über das Substrat die Anordnung der Moleküle in der Mischschicht beeinflusst werden kann. Unter Verwendung eines Transmissionselektronmikroskops lässt sich für die Mischschicht mit der optimalen Solarzellensubstrattemperatur von 110°C eine Phasenseparation von C60 und ZnPc unter Ausbildung von polykristallinen ZnPc Domänen in der lateralen Dimension von 50 nm nachweisen. Mit zusätzlichen Messungen der Ladungsträgerbeweglichkeiten des Mischschichtsystems kann die verbesserte Perkolation und Löcherbeweglichkeit von ZnPc für die Steigerung der Performance geheizter Solarzellen bestätigt werden. Desweiteren wird gezeigt, dass die Ausbildung einer Phasenseparation sehr stark von der darunter liegenden Molekülschicht z.B. der p-dotierte Löchertransportschicht abhängig ist. Im letzten und dritten Teil geht die Arbeit auf die Abhängigkeit der Klemmspannung von der Mischschichtkonzentration von C60 und ZnPc ein. Für die unterschiedlichen Volumenkonzentrationen von C60:ZnPc zwishen 6:1 und 1:6 kann gezeigt werden, dass sich die Ionisationspotentiale von C60 und ZnPc über einen großen Bereich linear und voneinander verschieden verändern und mit den absoluten Änderung der offenenen Klemmspannung korrelieren. Desweiteren wird gezeigt, dass sich durch eine zusätzlich an die Mischschicht angrenzende intrinsische ZnPc Schicht, abhängig von der Mischschichtkonzentration, Injektionsbarrieren ausbilden, welche nachweislich einen Spannungsverlust bedingen. Dabei kann gezeigt werden, dass der Spannungsverlust mit der ZnPc Schichtdicke und der Barrierenhöhe korreliert

Les propriétés des matériaux organiques pour l'optoélectronique à base de polymères ou de petites molécules sont fortement influencées par l'organisation moléculaire. En particulier, l'efficacité de la photoconversion dans les dispositifs à base de films minces organiques peut être corrélée directement à la morphologie de leurs mélanges actifs. Par conséquent, une meilleure compréhension de l'évolution de la morphologie des films minces pendant les divers traitements effectués lors de leur élaboration est essentielle et nécessaire. D'autre part, l'ingénierie moléculaire est un outil crucial pour l'obtention de molécules basées sur des alternances de fragments accepteurs d'électrons ou donneurs d'électrons et présentant des valeurs de gap électronique optimales et conduisant à des dispositifs aux paramètres de photoconversion optimisés.Dans le présent travail, nous présentons une étude approfondie en solution et sur des films minces de poly-3-hexylthiophène (P3HT) pur et en mélange avec des complexes de nickel (Ni-bdt). Le but était de comprendre comment le P3HT interagit avec les complexes de nickel pour contrôler des phénomènes d'organisation éventuels. L'objectif principal de cette étude est de comprendre l'organisation moléculaires au sein des films organiques et son impact sur le transfert de charge entre les matériaux afin d'optimiser les rendements de photoconversion. En outre, nous avons conçu et synthétisé trois nouvelles molécules à faible gap électronique, nommées SilOCAO, Bz(T1CAO)2 et Bz(T1CAEH)2 selon des méthodologies de synthèse optimisées. Ces molécules ont été conçues avec l'appui de calculs semi-empiriques effectués avec le programme Gaussian 09 au niveau B3LYP/6-31G* dans le but de les associer éventuellement aux complexes de nickel. Leurs synthèses et caractérisations complètes sont décrites en détail. Les techniques analytiques utilisées sont la spectroscopie d'absorption UV-visible, la photoluminescence, la résonance magnétique nucléaire (RMN), la spectroscopie de masse, l'électrochimie, l'analyse thermogravimétrique (TGA) et la calorimétrie différentielle à balayage (DSC). Ces molécules présentant des propriétés intéressantes pour leur utilisation en photovoltaïque organique, nous avons réalisé des cellules solaires organiques prototypes. Les résultats obtenus sont prometteurs, en particulier dans le cas de la molécule SilOCAO, utilisée ici comme donneur d'électrons en association avec le PC71BM. Ce travail est le fruit d'une collaboration précieuse entre plusieurs chercheurs, des théoriciens et expérimentateurs, des laboratoires LAAS et LAPLACE à Toulouse (France), de l'Université Autonome Nationale de Mexico (UNAM) et du Centre de Recherche en Optique (CIO) de Leon (Mexique)
Optoeletronic properties of semiconducting polymeric/small molecules materials are highly influenced by molecules organization. In particular, photoconversion efficiency of organic devices may be correlated directly with their blend morphology. Therefore, a better understanding of the blend film morphology evolution during postproduction treatment and device performance is essential and needed. On the other hand, molecular engineering is a good way to module the band gap of molecules by alternating different electron acceptor or electron donor moieties which may lead to an improved internal charge transfer and a low band gap to achieve important Voc and Jsc, and consequently a good OPV performance. In the present work, we present a comprehensive study in solution and on thin films of pristine P3HT and of some nickel bisdithiolene complexes (Ni-bdt), and their blends, in order to understand how poly(3-hexylthiophene) P3HT interacts with the nickel core with the aim of understanding eventual organization phenomena. The main goal of this study is to understand materials organization and the charge transfer effect between donor and acceptor molecules, rather than focalize on a high photoconversion yields. In addition, we have developed 3 new low band gap small molecules, SilOCAO, Bz(T1CAO)2 and Bz(T1CAEH)2 with innovating synthetic methodologies and interesting applications to be used in thin film bulk heterojunctions (BHJs) for organic photovoltaics. These molecules were strategically designed via semi-empirical calculations (B3LYP/6-31G*) to match their energetic levels (LUMO and HOMO) with those of nickel bisdithiolene family towards a performing charge transfer. The syntheses of SilOCAO, Bz(T1CAO)2 and Bz(T1CAEH)2 have been described. These molecules have been fully-characterized by different techniques such as UV-Visible Spectroscopy, Electroluminescence, Nuclear Magnetic resonance (NMR), Mass Spectroscopy (MS), Electrochemistry, Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Moreover, we have performed organic solar cells prototypes with some promising results, specifically for SilOCAO as the electron-donor in counterpart of the PC71BM as the electron-acceptor. This work is a fruitful collaboration between several laboratories, researchers, technical servers and students from LAAS and LAPLACE in France, and IIM (UNAM) and CIO in Mexico

碩士
國立臺灣大學
應用物理所
100
This thesis contains two parts to investigate two new types of organic solar cell. The first one is about adding third polymer in the binary blend type of organic solar cells, thus it can enhance the light harvesting or generate more bi-continues phase that can achieve better phase separation in the active layer, finally accomplish the purpose of cell performance improvement; In the second part, we aim to investigate the structure effect of Isoindigo based conducting polymer on the performance of solar cell. This polymer exhibits low bandgap and is available from plant. We use it to make photovoltaic device and tune process conditions to optimize the performance of solar cell. In the first part, the experimental systems are poly(3-hexylthiophene) [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) and Poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b'']dithiophene-2,6-diyl]]-C61-butyric acid methyl ester (PCPDTBT: PC61BM), P3HT has good crystalline phase after annealing while PCPDTBT has better absorption in the NIR spectra and high Voc. In our experimental design we add low weight ratio of PCPDTBT and P3HT respectively in the P3HT:PC61BM and PCPDTBT:PC61BM binary devices and they thus become ternary blend devices. We analyze the device by measuring the absorption spectra and external quantum efficiency (EQE), and find that both absorption intensity and external quantum efficiency of P3HT:PC61BM:PCPDTBT are obviously enhanced in the near infrared-visible spectrum compare to the P3HT:PC61BM binary system. In the case of PCPDTBT:PC61BM:P3HT, though the absorption intensity rises in the region related to the added P3HT, the enhancement of external quantum efficiency increases in almost from the UV-NIR region. For going into the details of this different causes of performance improvement, we utilize the atomic force microscopy (AFM) to observe those two systems, and we discover that the surface of P3HT:PC61BM:PCPDTBT smooth and better dispersed than that of P3HT:PC61BM, and the aggregations decreases; In contrast, PCPDTBT:PC61BM:P3HT ternary dissolved in CB+3% DiO has rougher surface, larger aggregation, thus contribute a decrease rate of charge recombination rate. Then we aim at PCPDTBT:PC61BM:P3HT system and further analyze it by transmission electron microscopy (TEM) and grazing incidence X-ray diffraction (GIXRD), thus acquire the PCPDTBT domain and PCBM clusters and detect the signal of P3HT (100) planes. For enhancing the light harvesting in visible spectrum and tuning the nano-morphology of thin film and binary system, we include third polymer in the original binary blend system, after optimizing the process, the best power conversion efficiency of P3HT:PC61BM:PCPDTBT system is slightly above 4.0%. It is about 10% higher than the highest one of P3HT:PC61BM: binary blend device which is due to the additional absorption in near infrared-visible region. The best PCEs value of PCPDTBT:PC61BM:P3HT dissolved in CB+ 3% DiO is 3.3%, which is also 10~20% higher than that of PCPDTBT:PC61BM. We can attribute the improvement to the morphology changes which result in moderate phase separation, so the above-mentioned phenomena confirm our prediction from the experimental design of this study. The second topic in the thesis is concentrated on the effect of Isoindigo device, a widely-used polymer in dye industry from one century ago, also a low band gap material, which is suitable for light harvesting donors for organic solar cells when blended with PCBM. We have evaluated four isoindigo polymers with different side-chain:PC8Ie, PCeI8, PC8I8,and PCeIe which are synthesized in our laboratory. In the attempt to optimize their device performance, we change the process by adding additive, different mixing ratio, and processing spin rate, because the structure of side chain (linear or branch), the length of side chain and the concentration of PCBM all can influence the charge mobility. Eventually, we obtain the best power conversion efficiency on different polymers: 4.0% in PCeIe:PCBM, 3.6% in PCeI8:PCBM, 3.3% in PC8I8:PCBM. Then, we measure and analyze the absorption spectra, external quantum efficiency, atomic force microscopy, and grazing incidence x-ray diffraction series of the active layer of these devices, thus we can provide useful information for manufacturing Isoindigo devices.

Research Doctorate - Doctor of Philosophy (PhD)
Over the last few years, promising development has been reported in organic photovoltaics. Typically, two organic semiconductors are blended as the active layer to absorb light and generate charges. To further improve the power conversion efficiency (PCE) a third material with complementary absorption spectrum can also be incorporated to enhance photon harvesting. Such a ternary system gives rise to more complex charge transfer and exciton dissociation mechanisms, which are explored in this thesis. In this thesis poly(3-hexyl thiophene): Phenyl-C60-butyric acid methyl ester: 2,4-bis [4-(N, N-diisobutylamino)- 2,6-dihydroxyphenyl] squaraine (P3HT:PCBM:DIBSq) system is used as a ternary model system. First, the exciton dissociation mechanism in the P3HT:PCBM:DIBSq material blend is analysed. The energy level diagram of this ternary system indicates that sufficient driving force is available at the interface between P3HT and DIBSq to dissociate excitons. However, an in depth study of charge generation in P3HT:PCBM:DIBSq films and photovoltaic devices shows that the P3HT:DIBSq interface is not capable of generating free charge carriers. An examination of energy transfer from P3HT to DIBSq in solution shows that hetero-energy transfer occurs efficiently. Indeed, energy transfer is found to occur in the solid state as well, which allows for a two-step exciton dissociation mechanism. A series of ternary (P3HT:PCBM:DIBSq) and binary (P3HT:PCBM) bulk hetero-junction (BHJ) organic photovoltaic (OPV) devices were fabricated to optimize their device performance. Binary P3HT:PCBM devices were found to have an optimized PCE of 3.8%. By comparison ternary devices with a DIBSq concentration of less than 1.5% by weight exhibited an improved PCE of 4.2% . As the DIBSq content is increased beyond 1.5 %, no further performance improvement is seen and the PCE steadily decreases. Transient electrical measurements reveal that the presence of DIBSq does not significantly decrease the charge carrier mobility, bimolecular recombination rate or charge generation efficiency of the blend. The charge collection efficiency, on the other hand, was found to steadily decrease with increasing DIBSq content. A morphological study using TEM and AFM shows that while the addition of DIBSq to the P3HT:PCBM blends does not alter the microstructure of the P3HT phase, DIBSq aggregates are formed. These aggregates increase in size as the DIBSq content increases and subsequently hinder charge extraction. Hence, the improvement in light absorption and charge generation due to DIBSq is completely negated by the reduction in charge extraction at high DIBSq concentrations. At low DIBSq concentrations (<1.5 wt. %), the advantage of the increased absorption due to DIBSq outweighs the negative effect on charge extraction and gives rise to an overall improvement in PCE. In general, the optimum performance in ternary systems is expected at the highest dye content that does not cause significant aggregation. Finally, ternary nanoparticles consisting of P3HT, PCBM and DIBSq were synthesized and their optical and structural properties characterised using transmission electron microscope (TEM), scanning electron microscope (SEM), atomic force microscope (AFM) and scanning transmission X-ray microscope (STXM) measurements. A series of photovoltaic devices were fabricated using aqueous P3HT:PCBM:DIBSq nanoparticles with DIBSq concentration varying from 0.5 wt.% to 22 wt.%. The marked difference in the morphology of the ternary nanoparticles compared to the BHJ structures means that a higher DIBSq concentration can be achieved before the PCE suffers. Devices with 14.3 wt.% DIBSq exhibited the highest performance with PCE of 1.1%, while the equivalent binary devices had a PCE of 0.41%. Enhanced optical properties, beneficial energy transfer and morphological properties of the ternary nanoparticles showed that the ternary concept is a promising strategy for improving the performance of aqueous nanoparticulate photovoltaic devices.

碩士
明志科技大學
材料工程系碩士班
105
In the first part of this study, we have prepared Phenothiazine -based small molecules and showed their application in organic photovoltaics (OPV). We fabricated PSCs with device structures of ITO (Indium tin oxide)/ZnO/ Phenothiazine -based small molecules /MoO3/Ag, where the ZnO and MoO3 were used to produce the n­type and p­type interlayers. We observed the best power conversion efficiency (PCE) of 2.6 % under simulated AM 1.5G irradiation (100 mW cm-2), with values of Jsc, Voc, and FF of 6.3 mA/cm2, 0.77 V, and 50.4 %, respectively. For the second part of this study, we demonstrated promising photovoltaic properties of ternary-blend polymer solar cells using a new combination of a conjugated polymer (PIDTBT: poly(indacenodithiophene–benzothiadiazole), nonfullerene acceptor (ITIC:3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2’,3’-d’]-s-indaceno [1,2-b:5,6-b’] dithiophene) and fullerene acceptor (PC71BM:[6,6]-Phenyl-C71-butyric acid methyl ester). We fabricated OPV device with structure of ITO (indium tin oxide)/zinc oxide (ZnO)/PIDTBT:ITIC:PC71BM/MoO3/Ag, where the ZnO and MoO3 were used as the n­type and p­type interlayers. We observed the best power conversion efficiency (PCE) of 6.8 % for the PIDTBT:ITIC:PC71BM devices under simulated AM 1.5G irradiation (100 mW cm-2), with values of short circuit current density (Jsc), open circuit voltage (Voc), and fill factor (FF) of 13.8 mA cm-2, 0.87 V, and 56.8 %, respectively.

Organic solar cells (OSC) have been emerging as promising energy harvesting technology because of their low-cost fabrication, semitransparency, solution processability and ability to be produced in large scale using roll-to-roll processing methods. It was envisaged that, resonance energy transfer (RET) is pivotal for improving device efficiencies of ternary blend solar cells (TBSCs). Taking analogy from natural photosynthetic systems, we have shown that mechanistic deviations of observed RET rates from an expected Förster type mechanism are anticipated in OSCs. But unlikely the highly efficient photosynthetic systems, blend morphology plays an important role in dictating the device performance of OSCs. We extracted new suggested strategies to systematically correlate the R0 with increments in current density (ΔJSC) and to optimize the effect of FRET in enhancing the photocurrent for realizing high efficiency OSCs. Chapter 2 and 3 discuss incorporation of a small molecule and polymer in fullerene and NFA based TBSCs, respectively. FRET between the donor components played an important role in enhancement of PCE and this was established by probing the excited state photophysics using both steady state and transient absorption (TA) spectroscopy. The fullerene based TBSCs had >300 nm thick active layer which implicates its potential application in roll-to-roll processable OSCs. In the NFA based TBSCs, we observed ≥ 10% increment in JSC, which enhanced PCE up to 10.34% for PTB7-Th:PBDB-T:IT4F blend. An important conclusion drawn from this work is although FRET plays an important role in enhancing device photocurrent, its extent is limited by blend morphology, synchronous with our finding in the first chapter. The ultrafast charge generation mechanism of a reported high-performing NFA based OSC, PM6:Y6 is discussed in Chapter 4. The PCE of ~15 % is achieved with external quantum efficiency > 70 % in the 400-900 nm region. TA spectroscopy was employed to understand the charge generation by probing both electron and hole transfer processes at ultrafast timescales. It was concluded that the slow hole transfer rate is limited by singlet exciton diffusion in Y6 molecule and is key to the observed dynamics of charge generation. These results also suggest that ultrafast charge transfer is not a necessary condition for efficient generation of free charges. In Chapter 5, we reported synthesis of three new conjugated copolymers with high dielectric constant (εr). To improve the εr of semiconducting polymers, we followed a two-pronged approach: (i) introduction of TEG sidechains in D-A type semiconducting polymers to enhance the dipolar polarization and (ii) variation in electron-donating strength of donor chromophores in the polymer backbone. This led to the achievement of εr ~ 4-5 at room temperature in MHz frequency range. However, free charge generation could not be achieved for any of the polymers, which is possibly because the low electronic polarization of TEG groups rendering the screening of hole and electrons ineffective. We conclude that concerted efforts should be made to not only improve the εr in MHz frequency regime but also in high frequency regime so as to achieve free charge carrier generation.

碩士
明志科技大學
材料工程系碩士班
106
In this study, we demonstrated promising photovoltaic properties of ternary-blend polymer solar cells using a new combination of a conjugated polymer (PTB7-Th : Poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b’]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)], nonfullerene acceptor (N2200 : Poly{[N,N'-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} and fullerene acceptor (PC71BM:[6,6]-Phenyl-C71-butyric acid methyl ester). Thus, fullerene acceptors have better short absorption spectra, and nonfullerene acceptor N2200 have attracted much attention by their superior stability. We fabricated OPV device with structure of ITO (indium tin oxide)/zinc oxide (ZnO)/PTB7-Th:PC71BM:N2200/MoO3/Ag, where the ZnO and MoO3 were used as the n­type and p­type interlayers. We observed the best power conversion efficiency (PCE) of 7.7 % for the PTB7-Th:PC71BM:N2200 devices under simulated AM 1.5G irradiation (100 mW cm-2), with values of short circuit current density (JSC), open circuit voltage (VOC), and fill factor (FF) of 15.1 mA cm-2, 0.79 V, and 64.3 %, respectively.

Research Doctorate - Doctor of Philosophy (PhD)
This thesis will investigate how porphyrinic materials may be successfully incorporated into polymer/fullerene organic solar cells to broaden light absorption, enhance power conversion efficiency, and to further probe and broaden the understanding of the chemistry and physics of both binary and ternary blended organic solar cells. This thesis will begin with a discussion of bulk heterojunction organic solar cells, and how porphyrinic materials can be incorporated into these devices to form ternary blends, including a review of the ternary polymer:porphyrinoid:fullerene literature published to date. The performance of standard MEH-PPV:PCBM organic solar cells manufactured at the University of Newcastle during the course of this PhD will be examined to show how device efficiency has steadily improved over the course of the project (2007-2011). Furthermore, it will show that the incremental improvements made to the standard binary devices over time are directly transferable to ternary blend devices. The effect of systematically changing the steric bulk of a porphyrin on the performance of ternary blend devices is then investigated, as is the effect of changing the electronic states of the core while maintaining a constant steric profile. The effect on device performance of varying the para-phenyl substituents of a series of tetraphenylporphyrin derivatives is also examined. Finally, the effect of altering the central metal cation in a series of metalloporphyrins with octaethylporphyrins and tetraphenylporphyrins ligands is investigated. This thesis as a whole provides an insight into the chemistry and physics of ternary blend organic solar cells, detailing not only the interaction of porphyrin with polymer and fullerene, but also the effects of porphyrin-porphyrin interactions and how these may be controlled. Steric, electronic, and morphological effects are investigated, to provide a comprehensive study of ternary blend organic solar cells.

因為通過加入另一吸光組分可以擴大吸收光譜，三組分有機太陽能電池近年成為了提高光伏效率的重要方向。在有機太陽能電池的體異質結里，新加入的材料根据组分的不同可以作為其他材料的敏化劑，或者作為主要的協同吸光材料。本論文研究該兩種類型三組分太陽能電池并重點討論了組分形貌相容性的問題。在整個研究過程中，我採用同步輻射的掠入射X射線散射技術，從分子尺度到納米尺度來研究三元組分電池的形貌，并通過加深對形貌與性能之間關係的理解來進一步提高電池性能。
在敏化劑型三組分電池中，我將約6%的低帶隙聚合物PTB7加入到P3HT:PC71BM的體異質結中獲得了27%的效率提高。重要的是這個三組分系統在大於200nm的厚膜電池中仍然表現出高效率。這個工作給出了一個通過用高結晶性和高性能共聚物共混來製備高效率厚膜有機太陽能電池的新方法，對未來的大面積電池的製備工藝有借鑒作用。另外在協同型三組分電池的研究里，我採用等比例PTB7-Th和PPor-2作為施主來與PC71BM共混成有機層，并獲得了效率高達9%三組分有機電池。我發現相對於兩組分電池，三組分電池的短路電流和填充因子都有了很大的提升，主要是因為光吸收有增強，載流子遷移率增加，還有載流子的復合也大大減少。接著我繼續研究可以允許共聚物相似比例混合的相容性的通用規律。我用四個化學結構完全不同的聚合物與PC71BM組成六組不同的三組分系統，進行了形貌兼容性的研究。我發現共聚物分子的堆垛形式與相分離的程度是形貌兼容的關鍵。就此實驗結果我們得到了對共聚物選材的指導規律，因此可以擺脫相似化學結構的限制，從而擴大了三組分電池材料的選擇範圍。
Ternary organic solar cells are emerging as a promising strategy to enhance device power conversion efficiency by broadening light absorption range with the incorporation of additional light absorbing components. In the bulk heterojunction of organic active layer, the third component is incorporated as either a sensitizer or a parallel component based on the amount added. My thesis study covers both cases and the underlying mechanism of morphology compatibility in ternary organic solar cells. Throughout the studies, synchrotron based grazing incidence X-ray scattering is used to unveil the morphology of the ternary films from the molecular scale to nanometer scale and to promote the understanding of the morphology-device correlation in order to improve the device performance.
For the sensitizing case, I employed ~6% of the third component, PTB7, which is a high-performance low-bandgap polymer, into a prototypical binary system, P3HT:PC71BM and achieved 27% improvement in power conversion efficiency. Remarkably, this ternary system exhibited high PCE even with a thick active layer, ~200 nm, a thickness at which the efficiency of PTB7:PC71BM cell drops dramatically. It suggested a brand new route for high efficiency thick-film photovoltaic device, especially valuable for future large-scale solar cell manufacturing, via mixing one high-crystallinity polymer and one high-performance polymer. For the parallel case, same amount of two high-performance donor polymers, PTB7-Th and PPor-2 were blended with PC71BM. A PCE as high as 9% was achieved, mainly due to the increase of short circuit current and fill factor arising from the enhanced light absorption, better charge carrier mobility and reduced charge recombination. Following the previous two specific systems, I then moved on to find out the general rule for compatible polymers to allow comparable loadings of each component. Four donor polymers with totally different chemical structures and absorption ranges were combined mutually to form six distinct ternary systems with PC71BM. We find that morphology compatibility in terms of molecular packing and phase separation is the key to donor material selection, which relaxes the limitation of chemical structure similarity and greatly extends the donor candidate pool for future ternary organic solar cell research.
Mai, Jiangquan.
Thesis Ph.D. Chinese University of Hong Kong 2016.
Includes bibliographical references (leaves ).
Abstracts also in Chinese.
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Detailed summary in vernacular field only.
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碩士
國立交通大學
材料科學與工程學系所
106
In this study, we employed a simple concept of ternary blend system for organic solar cell. Through blending small molecule (SM-4OMe) which has comple-mentary absorption spectrum into the host binary system (PTB7-TH and PC71BM), we successfully broadened the range of absorption spectrum and obtained higher efficiency of harvesting sunlight. We synthesized SM-4OMe with the same benzodithiophene (BDT) unit as the donor of PTB7-TH, which leaded to good morphology compatibility by blending PTB7-TH, SM-4OMe and PC71BM together to form desired packing orientation in the ternary blend films. Moreover, fluorescence resonance energy transfer took place between PTB7-TH and SM-4OMe, generating more carriers to diffuse to the interface of donor and acceptor so that the higher short-circuit current was collected by electrodes and eventually the PCE was optimized. The best PCE of 10.3% was obtained by incorporating PTB7-TH:SM-4OMe:PC71BM at weight ratio 0.9:0.1:1.5 in chlorobenzene, processed with 2vol% 1,8-Diiodooctane (DIO). We only added slight amount of SM-4OMe to form ternary blend films for ensuring the desired packing orientation for the better carrier transport. The result showed the PCE for the single junction organic photovoltaics could be successfully enhanced by a facile ternary blend.

碩士
國立聯合大學
材料科學工程學系碩士班
108
In this study, we use the inverted organic solar cell structure. A different weight ratio of PC71BM was added ino the polymer donor PBDB-T and the polymer acceptor N2200 forming a ternary organic solar cell. The short-circuit current can be increased from 10.36 mA/cm2 to 12.78 mA/cm2, and a power conversion efficiency of 7.42 % can be obtained. To further understand the mechanism of the increased short-circuit current, thought the PL measurement, we can be clearly seen that the addition of PC71BM can effectively quench the fluorescence emitted by PBDB-T, indicating that PC71BM can help charge transfer. In addition, from AFM, the addition of PC71BM can reduce the surface roughness and form a smoother surface. From TEM, we observed a fibrous structure is produced without adding PC71BM. After adding PC71BM, the uniformity is getting better. When excessive addition, the fibrous structure disappeared, and PC71BM agglomerated to form a spherical structure, which can impede the transfer of charge. From the above results, the addition of PC71BM can increase the short-circuit current and increase the photoelectric conversion efficiency. Next, we used ITIC instead of PC71BM to observe the photoelectric properties. After measurement, we found that adding ITIC can result in 6.87% power conversion efficiency, mainly due to the short circuit current rising from 10.36 mA/cm2 to 11.45 mA/cm2. Though the PL masurement, ITIC can also absorb the fluorescence emitted by PBDB-T. From this result, it is known that this addition method is extensive.

This study focuses on the architectural modification of pin-type small-molecule organic solar cells, in particular on the absorption layer and its influence on the key solar cell parameters, such as short circuit current density, fill factor and open circuit voltage. Three different approaches have been applied to improve the match between the solar spectrum and the spectral sensitivity of organic solar cells. In the first part, deposition parameters such as substrate temperature, gradient strength and (graded) absorption layer thickness are evaluated and compared to organic solar cells with homogeneously deposited absorption layers. Moreover, the gradient-like distribution of the absorption layer is characterized optically and morphological effects have been extensively studied. In order to isolate the origin of the efficiency improvement due to the graded architecture, voltage-dependent spectral response measurements have been performed and gave new insights. The second part concentrates on the efficient in-coupling of converted UV light, which is usually lost because of the cut off properties of organic light in-coupling layers. Via Förster resonance energy transfer, the absorbed UV light is re-emitted as red light and contributes significantly to higher short circuit current densities. The correlation between doping concentration, simple stack architecture modifications and the performance improvement is duly presented. In the third and last part, the impact of tri-component bulk heterojunction absorption layers is investigated, as these have potential to broaden the sensitivity spectrum of organic solar cells without chemical modification of designated absorber molecules. Along with the possibility to easily increase the photocurrent, an interesting behavior of the open circuit voltage has been observed. Knowledge about the impact of slight modifications within the solar stack architecture is important in order to be able to improve the device efficiency for the production of cheap and clean energy.

This work deals with the investigation and research on organic solar cells. In the first part of this work we focus on the spectroscopical and electrical characterization of the acceptor molecule and fullerene derivative C70. In combination with the donor molecule zinc-phthalocyanines (ZnPc) we investigate C70 in flat and bulk heterojunction solar cells and compare the results with C60 as acceptor. The stronger and spectral broader thin film absorption of C70 and thus enhanced contribution to photocurrent as well as the similar electrical properties with respect to C60 result in higher power conversion efficiencies. In the second part, modifications of the blend layer morphology of a C60:ZnPc bulk heterojunction solar cell are considered. Using substrate heating during co-deposition of acceptor and donor, the molecular arrangement is influenced. Due to the additional thermal energy at the substrate the blend layer morphology is improved and optimized for a substrate heating temperature of 110°C. With transmission electron microscopy, molecular phase separation of C60 and ZnPc and the formation of polycrystalline ZnPc domains in a lateral dimension on the order of 50 nm are detected. Mobility measurements show an increased ZnPc hole mobility in the heated blend layer. The improved charge carrier percolation and transport are confirmed by the enhanced performance of such bulk heterojunction solar cells. Furthermore, we show a strong influence of the pre-deposited p-doped hole transport layer on the molecular phase separation. In the third part, we study the dependency of the open circuit voltage on the mixing ratio of C60 and ZnPc in bulk heterojunction solar cells. For the different mixing ratios we determine the ionization potentials of C60 and ZnPc. Over the various C60:ZnPc blends from 1:3 - 6:1, the ionization potentials change linearly, but different from each other and exhibit a correlation to the change in open circuit voltage. Depending on the mixing ratio an intrinsic ZnPc layer adjacent to the blend leads to injection barriers which result in reduced open circuit voltage. We hence determine a voltage loss dependent on ZnPc layer thickness and barrier height.:Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 15 2 History, Fundamentals, and Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.2 Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.2.1 Organic semiconductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.2.2 Photovoltaic principle and organic solar cells . . . . . . . . . . . . . . . . . ... . . 42 2.3 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 61 3 Materials & Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 63 3.1 Organic Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 63 3.1.1 Standard photoactive materials . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 63 3.1.2 Transport materials and dopants . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . 67 3.1.3 Material purification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 3.2 Sample preparation and vacuum tools . . . . . . . . . . . . . . . . . . . . . . . . .. . 70 3.2.1 Sample preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 70 3.2.2 Vacuum tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 70 3.2.3 Substrates and layer stacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 73 3.3 Solar cell characterization tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 77 3.3.1 J(V)-measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 3.3.2 EQE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 3.4 Further characterization tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 79 3.4.1 UPS and XPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 79 3.4.2 OFET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 81 3.4.3 AFM, SEM, TEM, and WAXRD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 3.4.4 Optical Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 3.5 Simulation and modeling software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 3.5.1 Optical simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 3.5.2 Electrical simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4 Results: C70 as acceptor molecule for organic solar cells . . . . . . . . . . . . . . 85 4.1 Optical characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 4.2 Mobility measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 88 4.3 Ultraviolet photoelectron spectroscopy . . . . . . . . . . . . . . . . . . . . . . .. . . 89 4.4 p-i-i flat heterojunction solar cells . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 90 4.4.1 Di-NPD/fullerene flat heterojunction solar cells . . . . . . . . . . . . . . . . . . 90 4.4.2 ZnPc/fullerene flat heterojunction solar cells . . . . . . . . . . . . . . . . . . . . 91 4.5 p-i-i bulk heterojunction solar cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 4.5.1 p-i-i mixed C60:C70:ZnPc bulk heterojunction solar cell . . . . . . . . . . . 99 4.6 Outlook: fullerene C84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 101 5 Results: Bulk heterojunction solar cells deposited on heated substrates . 103 5.1 150 nm thick C60:ZnPc blend layers in m-i-p bulk heterojunctions . . . . 103 5.2 60 nm thick C60:ZnPc blend layers in m-i-p bulk heterojunctions . . . . . 107 5.2.1 AFM and SEM measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 5.2.2 Absorption measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 5.2.3 X-Ray (WAXRD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 113 5.2.4 TEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. 116 5.2.5 OFET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. 119 5.2.6 C70:ZnPc m-i-p bulk-heterojunctions . . . . . . . . . . . . . . . . . . . . . . .. . 121 5.3 p-i-i bulk heterojunction solar cells deposited at 110°C . . . . . . . . . . . . 124 5.3.1 Influence of sublayer on blend layer morphology . . . . . . . . . . . . . . . . 128 6 Results: On the influence of Voc in p-i-i bulk heterojunction solar cells . . 137 6.1 Dependency of Voc on C60:ZnPc mixing ratio . . . . . . . . . . . . . . . . . . . . 137 6.2 Influence of different hole transport layers on C60:ZnPc . . . . . . . . . .. . 140 6.2.1 Red and blue illumination measurements . . . . . . . . . . . . . . . . . . . . . . 143 6.2.2 Optical characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 6.2.3 UPS measurements for different C60:ZnPc mixing ratios . . . . . . . . .. 148 6.3 Influence of thin ZnPc and C70 interlayers on Voc . . . . . . . . . . . . . . .. . 152 6.3.1 UPS measurements of blend/ZnPc interfaces . . . . . . . . . . . . . . . . . . . 155 6.3.2 Blend/ZnPc injection barrier: experiment and simulation . . . . . . . . . . 158 7 Conclusion and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
Diese Arbeit beschäftigt sich mit der Untersuchung und Forschung an organischen Solarzellen und gliedert sich in drei Teile. Im ersten Teil wird auf die spektroskopische und elektrische Charakerisierung des Fullerenderivates C70 eingegangen, welches als Akzeptormolekül in Kombination mit dem Donormolekül Zink-Phthalocyanin (ZnPc) in Flach- und Mischschichtheteroübergänge organischer Solarzellen Anwendung findet. Dabei wird das Molekül mit dem bisherigen Standard Akzeptormolekül C60 verglichen. Die deutlich stärkere und spektral verbreiterte Dünnschichtabsorption von C70, sowie die vergleichbaren elektrischen Eigenschaften zu C60 führen zu einer Effizienzsteigerung in den Flach- und Mischschichtsolarzellen, welche maßgeblich durch die Erhöhung des Kurzschlussstromes erreicht wird. Im zweiten Teil widmet sich diese Arbeit der Morphologiemodifizierung des Mischschichtsystems C60:ZnPc, welche durch Heizen des Substrates während der Mischverdampfung von Akzeptor- und Donormolekülen in organischen Mischschichtsolarzellen erreicht werden kann. Es wird gezeigt, dass mit der zusätzlichen Zufuhr thermischer Energie über das Substrat die Anordnung der Moleküle in der Mischschicht beeinflusst werden kann. Unter Verwendung eines Transmissionselektronmikroskops lässt sich für die Mischschicht mit der optimalen Solarzellensubstrattemperatur von 110°C eine Phasenseparation von C60 und ZnPc unter Ausbildung von polykristallinen ZnPc Domänen in der lateralen Dimension von 50 nm nachweisen. Mit zusätzlichen Messungen der Ladungsträgerbeweglichkeiten des Mischschichtsystems kann die verbesserte Perkolation und Löcherbeweglichkeit von ZnPc für die Steigerung der Performance geheizter Solarzellen bestätigt werden. Desweiteren wird gezeigt, dass die Ausbildung einer Phasenseparation sehr stark von der darunter liegenden Molekülschicht z.B. der p-dotierte Löchertransportschicht abhängig ist. Im letzten und dritten Teil geht die Arbeit auf die Abhängigkeit der Klemmspannung von der Mischschichtkonzentration von C60 und ZnPc ein. Für die unterschiedlichen Volumenkonzentrationen von C60:ZnPc zwishen 6:1 und 1:6 kann gezeigt werden, dass sich die Ionisationspotentiale von C60 und ZnPc über einen großen Bereich linear und voneinander verschieden verändern und mit den absoluten Änderung der offenenen Klemmspannung korrelieren. Desweiteren wird gezeigt, dass sich durch eine zusätzlich an die Mischschicht angrenzende intrinsische ZnPc Schicht, abhängig von der Mischschichtkonzentration, Injektionsbarrieren ausbilden, welche nachweislich einen Spannungsverlust bedingen. Dabei kann gezeigt werden, dass der Spannungsverlust mit der ZnPc Schichtdicke und der Barrierenhöhe korreliert.:Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 15 2 History, Fundamentals, and Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.2 Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.2.1 Organic semiconductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.2.2 Photovoltaic principle and organic solar cells . . . . . . . . . . . . . . . . . ... . . 42 2.3 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 61 3 Materials & Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 63 3.1 Organic Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 63 3.1.1 Standard photoactive materials . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 63 3.1.2 Transport materials and dopants . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . 67 3.1.3 Material purification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 3.2 Sample preparation and vacuum tools . . . . . . . . . . . . . . . . . . . . . . . . .. . 70 3.2.1 Sample preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 70 3.2.2 Vacuum tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 70 3.2.3 Substrates and layer stacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 73 3.3 Solar cell characterization tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 77 3.3.1 J(V)-measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 3.3.2 EQE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 3.4 Further characterization tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 79 3.4.1 UPS and XPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 79 3.4.2 OFET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 81 3.4.3 AFM, SEM, TEM, and WAXRD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 3.4.4 Optical Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 3.5 Simulation and modeling software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 3.5.1 Optical simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 3.5.2 Electrical simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4 Results: C70 as acceptor molecule for organic solar cells . . . . . . . . . . . . . . 85 4.1 Optical characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 4.2 Mobility measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 88 4.3 Ultraviolet photoelectron spectroscopy . . . . . . . . . . . . . . . . . . . . . . .. . . 89 4.4 p-i-i flat heterojunction solar cells . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 90 4.4.1 Di-NPD/fullerene flat heterojunction solar cells . . . . . . . . . . . . . . . . . . 90 4.4.2 ZnPc/fullerene flat heterojunction solar cells . . . . . . . . . . . . . . . . . . . . 91 4.5 p-i-i bulk heterojunction solar cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 4.5.1 p-i-i mixed C60:C70:ZnPc bulk heterojunction solar cell . . . . . . . . . . . 99 4.6 Outlook: fullerene C84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 101 5 Results: Bulk heterojunction solar cells deposited on heated substrates . 103 5.1 150 nm thick C60:ZnPc blend layers in m-i-p bulk heterojunctions . . . . 103 5.2 60 nm thick C60:ZnPc blend layers in m-i-p bulk heterojunctions . . . . . 107 5.2.1 AFM and SEM measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 5.2.2 Absorption measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 5.2.3 X-Ray (WAXRD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 113 5.2.4 TEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. 116 5.2.5 OFET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. 119 5.2.6 C70:ZnPc m-i-p bulk-heterojunctions . . . . . . . . . . . . . . . . . . . . . . .. . 121 5.3 p-i-i bulk heterojunction solar cells deposited at 110°C . . . . . . . . . . . . 124 5.3.1 Influence of sublayer on blend layer morphology . . . . . . . . . . . . . . . . 128 6 Results: On the influence of Voc in p-i-i bulk heterojunction solar cells . . 137 6.1 Dependency of Voc on C60:ZnPc mixing ratio . . . . . . . . . . . . . . . . . . . . 137 6.2 Influence of different hole transport layers on C60:ZnPc . . . . . . . . . .. . 140 6.2.1 Red and blue illumination measurements . . . . . . . . . . . . . . . . . . . . . . 143 6.2.2 Optical characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 6.2.3 UPS measurements for different C60:ZnPc mixing ratios . . . . . . . . .. 148 6.3 Influence of thin ZnPc and C70 interlayers on Voc . . . . . . . . . . . . . . .. . 152 6.3.1 UPS measurements of blend/ZnPc interfaces . . . . . . . . . . . . . . . . . . . 155 6.3.2 Blend/ZnPc injection barrier: experiment and simulation . . . . . . . . . . 158 7 Conclusion and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

博士
國立清華大學
工程與系統科學系
104
Over the past decade, organic photovoltaics (OPVs) experienced significant development in performance reaching the threshold needed for commercialization [power conversion efficiencies (PCE) ˃10%]. Due to their light weight, flexibility and low cost, OPV technology is highly promising in terms of industrial aspects. Besides, OPVs have the advantage of being able to be fabricated on flexible substrates which facilitate the use of mass production techniques such ink jet printing or various roll-to-roll techniques. All these attractive advantages urged researchers worldwide to address challenges facing OPVs technology commercialization such as achieving high performances, replacing toxic processing solvents and upscaling with low costs. In this thesis, we introduced two main issues discussing processing techniques for high device performances and replacing toxic processing solvents with more eco-friendly counterparts. Solvent additive with "dual functionality" has been introduced in small-molecule solar cells with significant enhancement in performance. The first function of this additive was that it controlled the morphology: the addition of 0.1% CP3MS (the additive) was sufficient to improve the film’s crystallinity and morphology. The second function was the spontaneous migration of the CP3MS molecules from the bulk to the interface between the active layer and the Al cathode, forming an ultrathin interlayer that acted as a buffer layer. PCE enhanced from 2.75% for devices without additives to 4.55% for devices containing 0.1% CP3MS. As promising approach to widen the light absorption in organic solar cells, "ternary approach" has been introduced as technique to enhance device performance. We combined two small-molecule donors with acceptor to form all-small molecule ternary solar cells. Improvement in device performance mainly attributed to the complementary absorption of the two donors. After addition of the molecular donor as third component to form the ternary blend, the crystallinity and morphology of the active layer were enhanced. This means that the molecular donor in the ternary blend has effective role on both the absorption and the morphology. Devices produced PCE of 6.3% in ternary blend system relative to 4.55% in binary blend system. As most of highest OPVs performances achieved using halogenated toxic solvents which are big obstacle toward industrialization and mass production. Replacing these toxic solvents with more eco-friendly solvents is urgent need for the upscaling OPVs. Toluene (Tol), a halogen-free solvent, was employed in the fabrication of molecular solar cells, achieving power conversion efficiency PCE higher than that obtained when using chlorinated counterparts. Halogen-free solvents have been also used for solvent vapor annealing (SVA) to control the morphology. We succeeded to achieve one of the highest PCE in molecular solar cells processed form halogen-free solvents (˃ 7%). The enhancement arose mainly from the improvement in the fill factor, due to morphological tailoring and favorable phase separation. PCE higher than 7% is one of the highest achieved so far when using halogen-free solvents for molecular solar cells processing A new green solvent, cyclopentyl methyl ether (CPME), has been also introduced as successful alternative to replace toxic halogenated solvent for efficient molecular solar cells. Tol as co-solvent has been introduced with various amounts in CPME forming different green solvent mixtures. Tol incorporation as a co-solvent with CPME combined with thermal annealing effect led to PCE of greater than 8% which is the highest to date for molecular solar cells processed from green solvent mixtures. Morphology plays the key role in the performance improvement under the effects of co-solvent and thermal annealing.

博士
國立交通大學
應用化學系碩博士班
101
The thesis is composed of three topics. In the first part, to understand the relation between the solid-state phase structures and the photophysical properties of Poly (2,3-diphenyl-1,4-phenylene vinylene) (DP-PPV) derivatives, three DP-PPV derivatives, P1-P3 were designed, synthesized via Gilch polymerization and characterized. Among the polymers, P1 is a reported highly emissive poly(2,3-diphenyl-5-hexyl-p-phenylene vinylene), and P2, and P3 are novel DP-PPV derivatives, which are purposely designed to bear hydrophobic and hydrophilic Percec-type dendrons at the 5-position of the phenylene units on their DP-PPV main chains. The bulkiness and hydrophobic-hydrophilic natures of the side chains show strong effects on photophysical properties of the polymers. The solutions and as-casted films of P1-P3 all show remarkably high photoluminescence (PL) efficiency (ΦPL) (> 80 % in chloroform solution, and > 63 % for the as-casted films) among the PPV-derivatives. However, ΦPL of P1 and P3 decrease significantly to 30 % after cooled their polymer melts to room temperature. Through the phase behavior analysis by differential scanning calorimetry (DSC), and phase structure analysis by wide angle X-ray diffraction (WAXD), the decrease of ΦPL can be elucidated and attributed to the ordering of the solid-state structures of P1 and P3. To our surprise, ΦPL of P2 is preserved even in an ordered solid-state phase, and it is insensitive to the structural ordering. Structural analysis by WAXD patterns of P2 revealed that the aliphatic dendritic side chains of P2 effectively disturbing the intermolecular π-π interactions among the conjugated backbones, which allows the preservation of ΦPL in the environment with ordered packing of DP-PPV molecules. The results of time-resolved PL decay experiments also confirmed that P2 possess long-lived decay time because of excitons confined more effectively for emissive emission. In the second part, the novel core-expanded naphthalene diimide derivatives containing fluorinated alkane or dendron were synthesized and characterized. Naphthalene diimides (NDIs) are excellent n-type materials applied in organic semiconductors. Introducing fluorinated dendron with different spacer into NDIs is to improve the solubility for the fabrication of solution-processd devices. We can preliminarily speculate their molecular arrangement in the crystalline phase by the analysis of DSC and POM. The information of optical and electrochemical properties were obtained from UV-Vis spectra and cyclic voltammograms, respectively. The LUMO values of BDTDYBMNDIs in the range of －4.41－－4.45 eV are suitable n-type materials for the application of OFET device. The electron-only devices were fabricated to achieve the electron mobilites by space charge limited current equation. The fluorous phase of the dendron mediates the self-assembly process by means of the fluorophobic effect and the structural analysis of XRD is stll in process. Combining electronic measurement with structural analysis will make this research important. In the third part, porphyrin, despite chosen by nature as light harvesting units, has not revealed its full potentials as a structural unit in porphyrin-incorporated polymers (PPors). Polymer solar cells (PSCs) utilizing PPors suffer from their low Jscs and FFs. To investigate the origins of the low performances and take the advantage of the strong Soret band absorption in the blue-light region, a novel PPor, PPor-DITT, were synthesized, characterized and used as a blue-light harvesting dopant in the ternary-blend PSCs. PPor-DITT features broad absorption in the blue-light region, because the Diindenothieno[2,3-b]thiophene (DITT) unit extended the conjugation in the polymer backbone. PPor-DITT/PC71BM based PSCs have a high Voc of 0.79 V, but limited Jsc of 2.98 mA cm-2, and FF of 0.33. The low Jsc and FF were attributed to the un-optimized morphology, as the PL quenching experiments demonstrated efficient electron transfer from the photoexcited PPor-DITT to PC71BM, but smooth AFM topography of PPor-DITT/PC71BM blend indicated the ideal interpenetrating network for charge transport was not reached. Using PPor-DITT as a blue-light harvesting dopant in an amorphous host leverage the strong 400–550 nm absorption band of PPor-DITT and circumvent the difficulties in reaching optimized morphology in the PPor/PCBM thin films. An addition of 2 wt% of PPor-DITT in ternary-blend PSCs resulted in a 10 % increase of EQE in the blue-light region, good Jsc of 7.98 mA cm-2, and FF of 0.59. On the contrary, in a crystalline host (P3HT), the PPor-DITT dopant significantly decreased the crystallinity of the host and led to large drops in FF and PCE. The study provides an alternative route and expands the application of PPors in PSCs as a blue-light harvester in ternary-blend PSCs using amorphous polymers as host.

The rise in the world population can be correlated with an increase in energy need. Fossil fuels are not going to able to cover this need in energy because not only are they limited, they also have a negative effect on the environment. A reason the more to switch renewable energy. One of the most popular renewable energy source is solar energy. The organic solar cell could be a low-cost, light-weight and flexible option for photovoltaics. This thesis will discuss the morphology of the active layer of an organic solar cell. The polymer poly(9,9-dioctylfluorenyl-2,7-diyl) and the fullerene derivate [6,6]-phenyl C61-butyric acid methyl ester were used as model components for the active layer. These two components were processed in different solvents, different ratios, different total concentrations and were either dip- or spin-coated on glass substrates. These samples were analyzed with atomic force microscopy, steady state and time resolved fluorescence and UV/Vis spectroscopy. The analysis show that the morphology of the films processed in chloroform and tetrahydrofuran would react very similar in α-phase and β-phase by dip- and spin-coated samples. Xylene would react the opposite as tetrahydrofuran and chloroform while ethylbenzene would react little with different samples.
De stijging in wereldpopulatie kan gelinkt worden met een stijging in energieverbruik. Het is niet aan te raden om fossiele brandstoffen te gebruiken voor deze energiestijging want niet alleen zijn ze beperkt aanwezig op aarde ook zijn ze niet goed voor het milieu. Een reden te meer om naar duurzame energie over te schakelen. Één van de meeste populaire energiebronnen is zonne-energie. Hierbij zou de organische zonnecel een goedkope, lichte en flexibele optie zijn. Deze thesis zal de morfologie van de actieve laag van een zonnecel bespreken. Het polymeer poly(9,9-dioctylfluorenyl-2,7-diyl) en het fullereen derivaat [6,6]-fenyl C61-butylzuur waren de twee model componenten voor de actieve laag. Deze twee componenten werden in verschillende oplosmiddelen, verschillende verhoudingen en verschillende totaal concentraties bereidt en werden vervolgens gedipcoated of gespincoated op glazen substraten. De stalen werden vervolgens geanalyseerd door atomic force microscopy, steady state en time resolved fluorescence en UV/Vis spectroscopy. De analyse toont dat de morfologie van de films bereidt in chloroform en tetrahydrofuraan gelijkaardig reageren in α- fase en β-fase bij gedipt- en gespincoaten stalen. Terwijl xyleen net omgekeerd reageert als chloroform en tetrahydrofuraan. Bij ethylbenzeen zou de fases maar heel weinig veranderen bij de verschillende stalen.