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Organic Semiconductors Based on Triazastarphene Towards 3D : Charge Transport in Crystalline Phase / Semiconducteurs organiques à base de triazastarphene : vers un transport tridimensionnel en phase cristallineLi, Qian 19 September 2019 (has links)
Depuis une trentaine d’années, les matériaux organiques semi-conducteurs sont l’objet de recherches fondamentales autant qu’appliquées. Cet intérêt s’explique par des propriétés communément absentes des matériaux inorganiques utilisés jusqu’à présent telles que leur légèreté, leur souplesse et leur mise en forme aisée par des techniques d’impression à bas coût. Cependant, la forte anisotropie de leurs propriétés électroniques, telles que la mobilité des charges, a limité leur intégration dans les appareils de la vie courante.Ainsi, le but de cette thèse est d’étudier de nouveaux concepts de structures moléculaires adaptées au transport de charge tridimensionnel (3D) en phase cristalline. Cette étude concerne la synthèse des molécules, la caractérisation de leurs propriétés optoélectroniques, la résolution de leur structure cristalline, des mesures de dispositifs électroniques ainsi que la modélisation de paramètres clés du transport de charge.Pour atteindre cet objectif, les règles de conception appliquées aux molécules linéaires appartenant à la série du TIPS-pentacene a été étendues à des molécule de symétrie C3h. Les molécules possèdent ainsi un cœur aromatique plan en forme d’étoile à trois bras auxquels sont ajoutés des substituants encombrants proches du centre. Deux empilements sont alors envisagés appelés empilement par les bras ou en colonne décalée pour lesquels un chemin de percolation des sauts de charge est attendu dans les 3 dimensions.Ainsi, 13 triazastarphenes substitués par des amines ou des phényles ont été nouvellement obtenus via des méthodes de synthèses originales et directes. De plus, des systèmes borofluorés ont pu être obtenus ainsi qu’une voie de synthèse originale d’un composé utilisé en OLED. D’autre part, la résolution des structures cristallines a permis d’identifier des empilements proches voir identiques de ceux escomptés. Par exemple, deux benzostarphenes présentent respectivement un empilement par les bras sur la moitié de la maille et un empilement en colonne décalée. Enfin, l’étude théorique a mis en évidence que le transport de charge devrait s’effectuer en 2D pour le premier cas et en 3D pour le second en phase cristalline.Finalement, ce travail décrit pour la première fois la synthèse de composés étendus et solubles en forme d’étoile basés sur un motif acridine. Au-delà des multiples études sur les propriétés de ces molécules ainsi que de leurs intégrations quelquefois réussies dans des dispositifs électroniques (OFETs ou cellules à solaires à perovskites), les nouvelles méthodes de synthèse et les empilements discutés en détails devraient contribuer à l’élaboration de nouvelles règles de conception de composé -conjugué et participer au développement de semi-conducteurs organiques de plus hautes performances. / The research in organic electronics has attracted worldwide attention due to the specific properties of organic materials such as lightness, flexibility, large scale processing ability and low production cost. Compared with inorganic materials, the strong anisotropy and low charge carrier transport mobility limit their integrations in commercial devices. This research aims at developing molecule systems leading to three-dimensional charge transport.To reach this goal, our design strategy is to expand the generally linear-shaped molecular structure into star-shaped structure with C3h symmetry. The designed molecules consist of a planar core of fused aromatic cycles to form efficient - stacking with neighboring molecules and of bulky groups located close to the center to increase the solubility of the materials and prevent 1D columnar packing. Thus, two supramolecular arrangements are speculated (arm and column packing) where charge hopping follows pathways in 3D.Based on this design, 13 triazastarphenes substituted directly by amine or phenyl groups were synthesized and thoroughly characterized. Their electronic properties were carefully determined by UV-visible absorption spectroscopy, cyclic voltammetry and DFT calculations. Results from single crystal XRD showed that the experimental packing is similar to model for few molecules. In detail, one amino-triazastarphene has shown a new 2D layer by layer packing motif, while benzo-triazastarphenes have led to column packing in one case and half arm packing for another as expected. In addition, theoretical approach highlighted 2D and 3D dimensionality for charge carrier transport for the two later examples in the crystal phase.Finally, this work is the first report about straightforward synthesis of extended C3h acridine derivatives. Even though the performances obtained from the devices (OFETs and perovskite solar cells) based on these materials did not reach state of the art performances, the novel synthetic method and the achievement of interesting molecular arrangement motifs in single crystal can contribute to the development of high-performance OSCs.
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Amplification circuits based on electrochemical transistorsKhan, Zia Ullah January 2009 (has links)
<p>Electrochemical Transistor(ECT) was reported by David Nilsson in 2002. Later,its dimensios were specified and a SPICE model was developed.</p><p>The main purpose of this diploma work is to check the performance of electrochemical transistors in amplifier circuits. Simple amplifier circuits were simulated using SPICE model of ECT. Lateral and Vertical structures of electrochemical transistors were patterned on orgacon sheet(provided by AGFA),with various electrolytes(EG010,MS-HEC & MS-L). Characteric curves and time responses of these transistors were studied and then were then used as an active component in single amplifier circuits. Screen printed ECT's were also checked with the best available electrolyte. Behaviour of self made and screen printed ECT's were compared on the basis of on-off ratio,slew rate,frequency response and gain. Screen printed transistors showed promising results having less deterioration with time but till an an input signal frequency of 2Hz only. Mismatch with simulation results and Shockley's equation were other findings after data analysis.</p><p><img src="file:///C:/DOCUME%7E1/zia/LOCALS%7E1/Temp/moz-screenshot.jpg" /><img src="file:///C:/DOCUME%7E1/zia/LOCALS%7E1/Temp/moz-screenshot-1.jpg" /></p>
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Fast-switching all-printed organic electrochemical transistorsAndersson Ersman, Peter, Nilsson, David, Kawahara, Jun, Gustafsson, Göran, Berggren, Magnus January 2013 (has links)
Symmetric and fast (∼5 ms) on-to-off and off-to-on drain current switching characteristics have been obtained in screen printed organic electrochemical transistors (OECTs) including PEDOT:PSS (poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid)) as the active transistor channel material. Improvement of the drain current switching characteristics is made possible by including a carbon conductor layer on top of PEDOT:PSS at the drain electrode that is in direct contact with both the channel and the electrolyte of the OECT. This carbon conductor layer suppresses the effects from a reduction front that is generated in these PEDOT:PSS-based OECTs. In the off-state of these devices this reduction front slowly migrate laterally into the PEDOT:PSS drain electrode, which make off-to-on switching slow. The OECT including carbon electrodes was manufactured using only standard printing process steps and may pave the way for fully integrated organic electronic systems that operate at low voltages for applications such as logic circuits, sensors and active matrix addressed displays. / <p>Funding Agencies|Lintec Corporation||</p>
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Design and Fabrication of Light-Emitting Electrochemical Cells / Design och tillverkning av ljusemitterande elektrokemiska cellerSandström, Andreas January 2013 (has links)
Glödlampan, en gång symbolen för mänsklig uppfinningsförmåga, är idag på väg att försvinna. Lysdioder och lågenergilampor har istället tagit över då dessa har betydligt längre livstid och högre effektivitet. Den tidigare så hyllade glödlampan anses numera vara en miljöbov, och förbud och restriktioner mot den blir allt vanligare. Trots detta så är de nya alternativen bara att betrakta som provisoriska steg på vägen mot en ideal ljuskälla, som idag tyvärr inte existerar. Lågenergilampor innehåller exempelvis kvicksilver, och utgör därmed ett direkt hot mot en användares hälsa. Både lysdioder och lågenergilampor består även av höga halter av andra tungmetaller, och är väldigt komplicerade att tillverka. Återvinning är därför ett måste, och en fullödig energibesparingsanalys måste ta hänsyn till den betydande energin som går åt vid tillverkningen. Till viss del kan detta lösas genom att göra komponenterna små och ljusstarka, men för att göra en sådan belysning angenäm används istället utrymmeskrävande och ofta energislukande lampskärmar. Lysdioder och lågenergilampor är helt enkelt bra, men långt ifrån perfekta.All elektronisk utrustning är idag beroende av metaller och inorganiska halvledare, vilket gör återvinning viktig och tillverkning komplicerad. Detta är kanske på väg att ändras då även organiska material, t.ex. plast, har visat sig kunna ha elektroniska egenskaper. Idag är organisk elektronik ett hett forskningsområde där material med liknande egenskaper som plast, fast med funktionella elektroniska egenskaper, undersöks och appliceras. Något som gör organiska material extra intressanta är att många kan lösas upp i vätskor, vilket möjliggör för skapandet av bläck. Detta leder i sin tur till möjligheter för användandet av storskaliga trycktekniker, t.ex. tidningspressar och bläckstråleskrivare, vilka leder till en stor kostnadsreduktion och förenklad tillverkning av lysande komponenter. Idag har plast redan ersatt många andra material i en mängd olika tillämpningar. Plastflaskor är vanligare än glasflaskor, och ylletröjor konkurerar idag med kläder gjorda av fleece och andra syntetiska fibrer. Med ljusemitterande plast finns det helt klart en möjlighet att en liknande utveckling kan ske även för lampor.Den här avhandlingen fokuserar på den fortsatta utvecklingen av den ljusemitterande elektrokemiska cellen (LEC), som 1995 uppfanns av Pei et al. LEC-tekniken använder sig av organiska halvledare för att konvertera elektrisk ström till ljus, men även en elektrolyt som möjliggör elektrokemisk dopning. Detta förbättrar den organiska halvledarens elektroniska egenskaper signifikant, vilket leder till mindre resistans och högre effektivitet hos den färdiga lysande komponenten.Visionen för denna och besläktade tekniker har sedan länge varit förverkligandet av en lysande tapet. Den här avhandlingen har försökt närma sig denna vision genom att visa hur en LEC kan uppnå hög effektivitet och lång livslängd, och samtidigt tillverkas i luft med storskaliga produktionsmetoder. Orsaker till en tidigare begränsad livslängd har identifierats och minimerats med hjälp av nya komponentstrukturer och materialformuleringar. En inkapslingsmetod presenteras också, vilken skyddar komponenten från syre och vatten som annars lätt reagerar med det dopade organiska materialet. Detta resulterar i en signifikant förbättring av livslängden.Genom att använda slot-die bestrykning och sprayning, båda kompatibla med rulle-till-rulle tillverkning, har möjligheter för storskalig produktion demonstrerats. Slutligen har en speciell metod för spraymålning av stora lysande ytor utvecklats. / The incandescent light bulb, once the very symbol for human ingenuity, is now being replaced by the next generation of lighting technologies such as the compact fluorescent lamp (CFL) and the light emitting diode (LED). The higher efficiencies and longer operational lifetimes of these new sources of illumination have led to the demise of the classic traditional bulb. However, it should be pointed out that the light sources that are taking over are better, but not perfect. The complex high-voltage electronic circuits and health hazardous materials required for their operation make them far from a sustainable eco-friendly option. Their fabrication is also complex, making the final product expensive. A new path forward might be through the use of plastics or other organic materials. Though not traditionally seen as electronically active, some organic materials do behave like inorganic semiconductors and substantial conductivity can be achieved by doping. Since plastics can be easily molded into complex shapes, or made into an ink using a solvent, it is expected that organic materials could revolutionize how we fabricate electronic devices in the future, and possibly replace inorganic crystals in the same way as plastics have replaced glass and wool for food storage and clothes. This thesis has focused on the light-emitting electrochemical cell (LEC), which was invented by Pei et al. in 1995. It employs organic semiconductors that can convert electricity to light, but also an electrolyte that further enhances the electronic properties of the semiconductor by allowing it to be electrochemically doped. This allows light-emitting films to be driven by a low-voltage source at a high efficiency. Unfortunately, the electrolyte has been shown to facilitate rapid degradation of the device under operation, which has historically severely limited the operational lifetime. Realizing the predicted high efficiency has also proven difficult. The purpose of this thesis is to bridge the gap between the LEC and the CFL. This is done by demonstrating efficient devices and improved operational lifetimes. Possible degradation mechanisms are identified and minimized using novel device architectures and optimized active layer compositions. An encapsulation method is presented, and shown to increase the LEC stability significantly by protecting it from ambient oxygen and water. The thesis further focuses on up-scaled fabrication under ambient air conditions, proving that light-emitting devices are compatible with solution-based and cost-efficient printing. This is achieved by a roll-to-roll compatible slot-die coating and a novel spray-depositing technique that alleviates problems stemming from dust particles and phase separation. A practical ambient air fabrication and a subsequent operation of light-emitting electrochemical cells with high efficiency are thus shown possible.
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Design and synthesis of and π-stacked conjugated oligomers and polymersJagtap, Subodh Prakash 16 March 2012 (has links)
Interchain interactions between π-systems have a strong effect on the properties of conjugated organic materials that find application in devices such as light emitting diodes (OLEDs), organic photovoltaics (OPVs), and field effect transistors (FETs). We have prepared covalently-stacked oligo(1,4-phenylene ethynylene)s and oligo(1,4-phenylene vinylene)s to study the influence of chain-chain interactions on the electronic structure of closely packed conjugated units. These serve as models for segments of conjugated materials in thin film devices. Extension of this concept has allowed us to prepare multi-tiered systems that display the influence of pi-stacking. The stacked architectures were prepared by multi-step synthesis of the scaffolds, followed by metal-catalyzed cross coupling reactions (Sonogashira, Heck, Suzuki couplings) to incorporate the conjugated oligomers. The optical and electrochemical properties of these stacked compounds and polymers were compared to their unstacked linear counterparts. These studies provide a platform for the exploration of the nature of charge carriers and excitons in a broad class of materials that have significant potential in addressing challenges in power generation, lighting and electronics.
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Amplification circuits based on electrochemical transistorsKhan, Zia Ullah January 2009 (has links)
Electrochemical Transistor(ECT) was reported by David Nilsson in 2002. Later,its dimensios were specified and a SPICE model was developed. The main purpose of this diploma work is to check the performance of electrochemical transistors in amplifier circuits. Simple amplifier circuits were simulated using SPICE model of ECT. Lateral and Vertical structures of electrochemical transistors were patterned on orgacon sheet(provided by AGFA),with various electrolytes(EG010,MS-HEC & MS-L). Characteric curves and time responses of these transistors were studied and then were then used as an active component in single amplifier circuits. Screen printed ECT's were also checked with the best available electrolyte. Behaviour of self made and screen printed ECT's were compared on the basis of on-off ratio,slew rate,frequency response and gain. Screen printed transistors showed promising results having less deterioration with time but till an an input signal frequency of 2Hz only. Mismatch with simulation results and Shockley's equation were other findings after data analysis. <img src="file:///C:/DOCUME%7E1/zia/LOCALS%7E1/Temp/moz-screenshot.jpg" /><img src="file:///C:/DOCUME%7E1/zia/LOCALS%7E1/Temp/moz-screenshot-1.jpg" />
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In Quest of Printed Electrodes for Light-emitting Electrochemical Cells: A Comparative Study between Two Silver InksNahid, Masrur Morshed January 2012 (has links)
This thesis presents a comparative study between two silver nanoparticle inks that were deposited using a Drop-on-Demand (DoD) inkjet printer, aiming at finding a functional ink that can be used to print electrodes in Light-emitting Electrochemical Cells (LECs). To achieve this, a DoD inkjet printer was installed and an acquaintance with the printer was attained. Among the two inks, one was employed as received while the other was reformulated, and successful deposition of both the inks was observed. During the reformulation process, it was seen that the highly volatile tetrahydrofuran (THF) solvent can be used to improve the ink properties, in contrast to what is recommended. After that, the inks were deposited on UV-ozone treated glass substrates, sintered at an elevated temperature under ambient conditions, and their specific resistances and thicknesses were measured. Finally, the inks were used to print the anode in a structured sandwich-cell LEC. The performance comparison was conducted by observing the emitted light of the LECs. The results indicate that the reformulated ink performs better, probably due to the lower silver concentration that results in flatter surface, which in turn effectively alleviates shorts.
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A Molecularly Switchable Polymer-Based Diode / En Molekylärt Switchbar Polymerbaserad DiodHultell Andersson, Magnus S. January 2002 (has links)
Despite tremendous achievements, the field of conjugated polymers is still in its infancy, mimicking the more mature inorganic, i.e. silicon-based, technologies. We may though look forward to the realisation of electronic and electrochemical devices with exotic designs and device applications, as our knowledge about the fundamentals of these promising materials grow ever stronger. My own contribution to this development, originating from an idea first put forward by my tutor, Professor Magnus Berggren, is a design for a switchable polymer-based diode. Its architecture is based on a modified version of a recently developed highly-rectifying diode,12 where an intermediate molecular layer has been incorporated in the bottom contact. Due to its unique ability to switch its internal resistance during operation, this thin layer can be used to shift the amount of (forward) current induced into the rectifying structure of the device, and by doing so shift its electrical characteristics between an insulating and a rectifying behaviour (as illustrated below). Such a component should be of great commercial interest in display technologies since it would, at least hypothetically, be able to replace the transistors presently used to address the individual matrix elements. However, although fairly simple in theory, it proved to be quite the challenge to fabricate the device structure. Machinery errors and contact problems aside, several process routes needed to be evaluated and only a small fraction of the batches were successful. In fact, it was not until the very last day that I detected the first indications that the concept might actually work. Hence, several modifications might still be necessary to undertake in order to get the device to work properly.
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Electrical characterization and investigation of the piezoresistive effect of PEDOT:PSS thin filmsSchweizer, Thomas Martin 19 April 2005 (has links)
The field of organic electronics is recently emerging in modern electrical applications. Organic light emitting diodes have been developed and are implemented in commercially available products. The novel materials are also used in sensor applications, utilizing their intrinsic physical, chemical and electrical characteristics. Poly(3,4-ethylenedioxythiophene): poly(styrene-sulfonic acid) (PEDOT:PSS) is one of the most successful organic conductive materials. Developed as antistatic coating, it is now used in other fields as well such as in electro-optical devices as transparent electrodes. One of the reasons for its widely spread use is that water-based dispersions in high quality are available. In addition, it is considered highly stable, resisting degradation under typical ambient conditions. For this work, the usability of PEDOT:PSS as active layer for electromechanical sensor applications was investigated. The electrical properties of the material were characterized including temperature dependencies and environmental influences. A piezoresistive effect with negative sign was found. It is small in magnitude and of the same order as the change in resistance due to geometrical effects. The piezoresistive effect is temperature dependent and increasing in magnitude with higher temperatures. An average longitudinal piezoresistive coefficient pi_l of -5.6x10-10 Pa-1 at room temperature has been evaluated. The transverse effect under the same conditions is opposite in sign and two thirds in magnitude of the lateral effect. The hole mobility of PEDOT:PSS follows an Arrhenius function and thus the resistivity has a negative temperature coefficient. Some other thermally induced effects have been observed such as de-doping of the material resulting in an irreversibly lowered conductivity. Due to the low thermal conductivity of the substrate material used, Joule heating of the samples played an important role during the characterization and was utilized to investigate the temperature dependencies. The change of resistance caused by an applied stress to the sample is small, with a gage factor smaller than one.
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Modulation Effects on Organic ElectronicsChen, Hang 30 November 2005 (has links)
A high aspect ratio epoxy mask has been built with Taiyo PSR4000BN on chemical sensing array chip. Thickness up to 200 and #61549;m and aspect ratio up to 16:1 have been achieved with this material. It is demonstrated that this material satisfies the mechanical and chemical requirements. A three-electrode system has been designed and built for electrochemistry in micro-cell on chip. Tests with poly(phenylenesulfide-phenyleneamine) (PPSA) demonstrates that it is possible to precisely tune the properties (Work function and resistance) of conducting polymer that has been cast on chip surface.
A new test platform GT03 has been fabricated and used to characterize the chemical effects on organic electronics. It is demonstrated that the chemical species in ambient environment can affect organic electronics properties on bulk, interface and electric contact. The contact resistance in organic field-effect transistors (OFETs) has been characterized with modified interdigitated structure (IDS). It is demonstrated that drain and source contact resistances can be calculated separately with modified four-point-probe measurements, and contact resistance and material bulk resistance are actually modulated by the gate electric field. Furthermore, the influence from oxygen doping in poly(3-hexylthiophene) (P3HT) based OFETs has been investigated. A new model of oxygen doping has been suggested and it is demonstrated that oxygen doping can affect all the resistance components in P3HT OFETs.
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