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Quinoline derivatives are promising materials for optoelectronic and biomedical applications. A simple and scalable aza-Diels-Alder reaction of imine, napthyl alkyne was described for the synthesis of various chloroquinoline derivatives, benzoquinolines, and corresponding polybenzoquinolines. The exploitation of quinoline derivatives with different functionalities demonstrates the great potential not only for organic electronics but also for the molecular transformation for a board range of researchers.

Funder: Royal Society; Id: http://dx.doi.org/10.13039/501100000288, Funder: Winton Programme for the Physics of Sustainability, Conjugated polymers are an important class of chromophores for optoelectronic devices. Understanding and controlling their excited state properties, in particular, radiative and non‐radiative recombination processes are among the greatest challenges that must be overcome. We report the synthesis and characterization of a molecularly encapsulated naphthalene diimide‐based polymer, one of the most successfully used motifs, and explore its structural and optical properties. The molecular encapsulation enables a detailed understanding of the effect of interpolymer interactions. We reveal that the non‐encapsulated analogue P(NDI‐2OD‐T) undergoes aggregation enhanced emission; an effect that is suppressed upon encapsulation due to an increasing π‐interchain stacking distance. This suggests that decreasing π‐stacking distances may be an attractive method to enhance the radiative properties of conjugated polymers in contrast to the current paradigm where it is viewed as a source of optical quenching.

Curved X‐ray detectors have the potential to revolutionize diverse sectors due to benefits such as reduced image distortion and vignetting compared to their planar counterparts. While the use of inorganic semiconductors for curved detectors are restricted by their brittle nature, organic–inorganic hybrid semiconductors which incorporated bismuth oxide nanoparticles in an organic bulk heterojunction consisting of poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) and [6,6]‐phenyl C71 butyric acid methyl ester (PC70BM) are considered to be more promising in this regard. However, the influence of the P3HT molecular weight on the mechanical stability of curved, thick X‐ray detectors remains less well understood. Herein, high P3HT molecular weights (>40 kDa) are identified to allow increased intermolecular bonding and chain entanglements, resulting in X‐ray detectors that can be curved to a radius as low as 1.3 mm with low deviation in X‐ray response under 100 repeated bending cycles while maintaining an industry‐standard dark current of, Solution processable organic–inorganic hybrid semiconductors for flexible curved X‐ray detector components have the potential to revolutionize diverse sectors in terms of its cost and performance. This work introduces a strategy for realizing the optimum balance for detector performance at low operating voltages with mechanical flexibility by tuning the organic semiconductor molecular weight for such curved hybrid detectors.

A review of publications on the synthesis and properties of a family of compounds called perinones was carried out. The basic molecule has been known for several decades mainly as a photostable pigment, and in recent years it has become increasingly used in organic electronics. This paper describes the methods of synthesis of low molecular weight compounds and polymers based on that molecule; the basic spectroscopic, photochemical, electrochemical and electronic properties important for the construction of organic electronics and optoelectronics devices are also discussed.

Photovoltaic (PV), which converts sunlight into electricity, is a promising solution to the energy and environmental crisis we are facing right now. In this dissertation, we are focusing on next generation semiconductors as the photoactive materials, i.e. organic and orgainic/inorganic hybrid perovskite semiconductors, to achieve cost effective and energy efficient solar cell technology. Organic semiconductor always shows narrow absorption compared with the conventional inorganic semiconductors, which is one of the limiting factors of the organic photovoltaic (OPV). In the second chapter, we solve this problem by employing the multi-absorber bulk heterojunction (BHJ) device architecture, in which different polymer absorbers are blended together to cover panchromatic absorption. A comparison study reveals the working mechanism of this novel device, and the material selection rule is summarized. Eventually, the 8.7% power conversion efficiency is realized in ternary BHJ solar cell. Besides the narrow absorption, the organic BHJ layer is usually very thin (~100 nm) due to its limited carrier mobility, hence the absorption is insufficient in the photoactive layer. In the third chapter, we utilize the plasmonic effect of the metal nanoparticle to enhance the absorption of the OPVs. The addition of spectrally tuned SiO2-Au nanorods leads to improved photocurrent and device efficiency. On the other hand, the narrow absorption of organic materials also creates new device possibility that traditional semiconductor can't deliver. One of the good examples is the visibly semitransparent solar cells. In the fourth chapter, we develop this idea by engineering transparent top electrode and incorporate photonic distributed bragg reflector to further improve the device efficiency without compromising the visible transparency. Organic/inorganic hybrid perovskite semiconductor attracts incredible attentions in the past few years. It originates from the excitonic semiconductor family but delivers superior photovoltaic device performance than the typical excitonic solar cell e.g. dye sensitized solar cells and organic solar cells. However, the photophysics of this type of material is still mysterious in many aspects. In the fifth chapter, we try to understand its photophysical property by some basic characterization methods. We discover that the photo excitations in this materials varies with different crystal size. Besides, we observe the photoluminescence lifetime and intensity improve dramatically after exposing to the moisture. The improved photophysical property eventually results in greatly enhanced photovoltaic device performance. In addition to the solar cell, we successfully demonstrates the ultral high photodetectivity based on the perovskite materials, the results are included in sixth chapter.

International audience; Les diodes organiques électro­lu­mi­nes­centes (OLEDs) sont des dispositifs électroniques capables d’émettre de la lumière sous l’effet d’un champ électrique. L’architecture de base d’une OLED consiste en un film mince émetteur de lumière (EML) déposé entre deux électrodes. Il existe quatre générations d’OLEDs différenciées par le processus photo-physique conduisant à l’émission de la lumière : l’OLED fluorescente, l’OLED phosphorescente, l’OLED TADF et l’OLED hyperfluorescente. Cet article présente les quatre générations d’OLEDs pour lesquelles le mécanisme d’émission de lumière est discuté à la lumière d’exemples sélectionnés dans la littérature.

A new printable organic semiconducting material combination as a tissue equivalent photodetector for indirect X-ray detection is demonstrated in this work. The device exhibits a higher optical-to-electrical conversion efficiency than any other reported printable organic systems for X-ray photodetection while also operating efficiently with zero applied bias. Complete X-ray detectors fabricated by coupling the photodiode with a plastic scintillator are among the first flexible and fully tissue equivalent X-ray detectors capable of operating without external bias. The response to X-rays is energy independent between 50 keV and 1.2 MeV, with a detection sensitivity equivalent to inorganic direct X-ray detectors and one of the fastest temporal responses ever reported for organic X-ray detectors. The materials can be printed into arrays with a pixel pitch of 120 μm, providing 2D spatial detection. The devices are found to be highly stable with respect to time, mechanical flexing, and large (5 kGy) radiation doses. The new materials and fully tissue equivalent X-ray detectors reported here provide stable, printable, flexible, and tissue equivalent detectors with a high radiolucency that are ideally suited for wearable applications, where simultaneous monitoring and high transmission of the X-ray absorbed dose into the human body is required.

Molecular systems have proven to be efficient active materials in electronics, making then suitable substitutes of the inorganic semiconductors used nowadays in electronic devices. For this reason, organic electronics has emerged as a research field with great potential and interest. In this project we have studied, both experimentally and theoretically, two ladder-type compounds functionalized with naphthalimides (Figure 1). The two molecular systems have been implemented in organic field effect transistors (OFETs), to assess their potential as active materials in organic electronics. Both compounds show p-type type mobility, moreover, NDI-TP-Ph-TP material also displays low n-type mobility, presenting a certain ambipolar character. The nature and stability of the charged species involved in the charge transport process have also been studied by spectroelectrochemical experiments. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

Metal and metalloid phthalocyanines are an abundant and established class of materials widely used in the dye and pigment industry as well as in commercial photoreceptors. Silicon phthalocyanines (SiPcs) are among the highest-performing n-type semiconductor materials in this family when used in organic thin-film transistors (OTFTs) as their performance and solid-state arrangement are often increased through axial substitution. Herein, we study eight axially substituted SiPcs and their integration into solution-processed n-type OTFTs. Electrical characterization of the OTFTs, combined with atomic force microscopy (AFM), determined that the length of the alkyl chain affects device performance and thin-film morphology. The effects of high-temperature annealing and spin coating time on film formation, two key processing steps for fabrication of OTFTs, were investigated by grazing-incidence wide-angle X-ray scattering (GIWAXS) and X-ray diffraction (XRD) to elucidate the relationship between thin-film microstructure and device performance. Thermal annealing was shown to change both film crystallinity and SiPc molecular orientation relative to the substrate surface. Spin time affected film crystallinity, morphology, and interplanar d-spacing, thus ultimately modifying device performance. Of the eight materials studied, bis(tri-n-butylsilyl oxide) SiPc exhibited the greatest electron field-effect mobility (0.028 cm2 V-1 s-1, a threshold voltage of 17.6 V) of all reported solution-processed SiPc derivatives.

The [1]benzothieno[3,2-b][1]benzothiophene (BTBT) planar system was used to functionalize the phthalocyanine ring aiming at synthesizing novel electron-rich π-conjugated macrocycles. The resulting ZnPc-BTBT and ZnPc-(BTBT)4 derivatives are the first two examples of a phthalocyanine subclass having potential use as solution-processable p-type organic semiconductors. In particular, the combination of experimental characterizations and theoretical calculations suggests compatible energy level alignments with mixed halide hybrid perovskite-based devices. Furthermore, ZnPc-(BTBT)4 features a high aggregation tendency, a useful tool to design compact molecular films. When tested as hole transport materials in perovskite solar cells under 100 mA cm-2 standard AM 1.5G solar illumination, ZnPc-(BTBT)4 gave power conversion efficiencies as high as 14.13 %, irrespective of the doping process generally required to achieve high photovoltaic performances. This work is a first step toward a new phthalocyanine core engineerization to obtain robust, yet more efficient and cost-effective materials for organic electronics and optoelectronics.

The objective of this PhD is to synthesize π-conjugated bio-based polymers from vanillin, with potential applications in the field of organic electronic (photovoltaic, Organic Light Emitting Diode, OLED). Polyazomethines with high molar masses were obtained via the copolymerization of divanillin with various diamines. This polycondensation was performed in 5 minutes under microwave irradiation, followed by solvent removal using a rotary evaporator. Divanillin-based polyazomethines absorb in the near-UV range but have a short conjugation pathway, as revealed investigations on model compounds. To improve this conjugated pathway, a divanillin-based molecule bearing aldehyde functions in para positions with respect to the link between the rings, was designed. This so-called para-divanillin, never reported before, was copolymerized to yield polyazomethines. These latter polymers also have a short conjugation pathway due to steric hindrance between the two aromatic rings of the para-divanillin skeleton. A last family of divanillin-based polymers was thus investigated: polythiazolothiazoles. The latter exhibit specific emission properties as they emit in the blue range in solution and in the yellow range in films. Benzothiazole-based model compounds were also synthesized and exhibited a fluorescence quantum yield of 20% and “herringbone-like” π-stacking, giving them a strong potential for various organic electronic applications.; Ces travaux de thèse portent sur la synthèse de polymères π-conjugués biosourcés issus de la vanilline, visant des applications potentielles en électronique organique (photovoltaïque ou Organic Light Emitting Diode, OLED). Des polyazométhines de masses molaires élevées, issus de la copolymérisation entre la divanilline et différentes diamines, ont été obtenus par polymérisation sous irradiation micro-onde durant 5 minutes puis séchage à l’évaporateur rotatif. Ces derniers ont une absorbance dans le proche UV mais un chemin de conjugaison très court, comme l’a révélé l’analyse de molécules modèles. Pour améliorer ce chemin de conjugaison, une molécule à base de divanilline a été synthétisée avec les fonctions aldéhyde en position para par rapport à la liaison entre les deux cycles aromatiques. Cette para-divanilline, encore jamais décrite, a été utilisée pour la synthèse de polyazomethines. Ces derniers présentent également un court chemin de conjugaison en raison de l’encombrement stérique entre les deux groupes phényle. Une dernière famille de polymère a alors été étudiée : les polythiazolothiazoles à base de divanilline. Ces polymères présentent des propriétés d’émission qui se caractérisent par une émission dans le bleu en solution et dans le jaune à l’état de film. Des molécules modèles à base de benzothiazole ont également été synthétisées et présentent un rendement quantique de fluorescence de 20% ainsi qu’un empilement π en « chevrons », leur conférant un fort potentiel pour diverses applications en électronique organique.

In this thesis, the study focuses on the synthesis of semi-conducting polymers by an original pathway free from metals, in order to integrate them into organic electronic devices such as OLEDs (Organic light emitting diodes). The aim is to develop and optimize a new methodology using acyclic bis-aminoarylcarbenes as building blocks to synthesize new PPV-like polymers. First, the dimerization reaction is studied at a molecular level with the synthesis and characterization of diaminoalkenes obtained from monofunctional acyclic aminoarylcarbenes. The mechanism and the selectivity of this dimerization reaction is also investigated experimentally and theoretically. In a second step, the dimerization reaction was extended at a macromolecular level with the synthesis and characterization of new PPV-like polymers containing amino functions in α of the double bond. Subsequently, the influence of these chemically modified amino groups on the optoelectronic properties of these N-PPVs has been studied. Finally, the specific characteristics of the diaminoalkenes synthesized during this thesis has allowed a preliminary study on their potential applications as organocatalysts in the atom transfer radical polymerization reaction.; Dans cette thèse, la synthèse de polymères semi-conducteurs par une voie originale n’utilisant pas de métaux, afin de les intégrer dans des dispositifs électroniques organiques comme les OLED (Organic light emitting diode) a été developpée. Le but est de développer et d’optimiser une nouvelle méthode de synthèse en s’appuyant sur des bis-aminoarylcarbènes acyclique en tant que blocs constructeurs afin d’obtenir de nouveaux polymères PPV-like. Dans un premier temps, la réaction de dimérisation est étudiée au niveau moléculaire avec la synthèse et caractérisations de diaminoalcènes obtenu à partir de carbènes acycliques monofonctionnels. Le mécanisme et la sélectivité de cette réaction de dimérisation ont également été examiné par voies expérimentales et théoriques. Dans un deuxième temps, la réaction de dimérisation a été étendu au niveau macromoléculaire avec la synthèse et caractérisations de nouveaux PPV-like polymères contenant des fonctions amino en α de la double liaison. Par la suite, l’influence de ces groupements amino sur les propriétés optoélectroniques de ces N-PPV une fois modifiés chimiquement a pu être étudié. Enfin, les caractéristiques particulières des diaminoalcènes synthétisés au cours cette thèse ont permis une étude préliminaire sur leurs applications potentielles en tant que catalyseur organiques dans la réaction de polymérisation radicalaire par transfert d’atomes.

As células eletroquímicas emissoras de luz (LEECs) são um dos tipos mais simples de dispositivos eletroluminescentes no estado sólido. Geralmente, elas são construídas com apenas uma camada contendo o material emissor. A camada ativa (CA) das LEECs consiste em um material emissor misturado com um eletrólito polimérico ou espécies iônicas. Com exceção do eletrólito, sua estrutura é semelhante à de um diodo orgânico emissor de luz (OLED) de camada única. As LEECs, além de poderem mostrar as mesmas vantagens tecnológicas dos OLEDs, podem apresentar outras vantagens adicionais, tais como: (i) baixa dependência da função de trabalho dos eletrodos, (ii) baixa dependência com a espessura da CA, (iii) baixa tensão de operação, alto brilho e (iv) as LEECs podem ser impressas em grandes áreas. Neste trabalho, foi sintetizado uma série de novos líquidos iônicos (LIs) derivados de 1,2,3-triazólio e seus intermediários com o intuito de investigar o desempenho dos LIs em LEECs. Neste contexto, foram sintetizados oito LIs com quatro tamanhos de cátions diferentes e dois ânions (iodeto e trifluorometanossulfonato). Estes LIs foram aplicados como eletrólitos em LEECs. Todos os dispositivos foram fabricados com o poli[2-metoxi-5-(2-etil-hexiloxi)-1,4-fenilenevinileno] (MEH-PPV) comercial como polímero emissor. De acordo com os resultados obtidos, foi mostrado que o dispositivo com o melhor desempenho alcançado foi com 4% do LI dohmtI e 80 nm de CA, apresentando uma alta luminância de 3,2x104 cd/m2. Apesar do MEH-PPV não ser tão eficiente quando comparado com o estado da arte dos novos materiais emissores empregados hoje em dia, os estudos apresentados apontam que os novos LIs derivados de 1,2,3-triazólio foram capazes de fornecer os requisitos necessários para serem usados como eletrólito de LEECs. The Light-Emitting Electrochemical Cell (LEEC) is one of the simplest kind of electroluminescent solid-state devices. Generally, they are fabricated with only one emitting material layer (EML), so-called active emission layer, that consist of an emitter material mixed with an ionic electrolyte. Apart from the electrolyte, their structure is similar to that of a single layer organic light-emitting diode (OLED). Not only LEECs assemble most of OLEDs applications and their technological advantages, but they also bring additional ones such as (i) low dependence of the electrodes work function, (ii) low dependence to the EML thickness, (iii) low operation voltage and high brightness and finally (iv) LEECs can be printed or sprayed in large areas. In this work, it was synthesized a series of new ionic liquid (IL) based on 1,2,3-triazolium and their intermediates to investigate the performance of the ILs in LEECs. In this context, it was synthesized eight ILs with four different cations size and two anions (iodide and trifluoromethanesulfonate). These ILs were applied as electrolyte for LEECs. All devices were fabricated with a commercial poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) as emitter polymer. As a result, we showed that the best device performance was achieved with 4% of dohmtI and 80 nm of active layer, presenting a luminance of 3.2x104 cd/m2. Despite the use of the MEH-PPV, a polymer not so efficient when compared to the state-of-art of the novel emitter material employed nowadays, our realization showed these new ILs based on 1,2,3-triazolium have been able to provide the specific requirements of the LEEC devices.

La sintesi e la caratterizzazione di semiconduttori organici (OS) è stata un ambito di ricerca molto sviluppato negli ultimi due decenni. La loro potenziale applicazione per dispositivi come transistor a effetto di campo organici (OFET), diodi organici a emissione di luce (OLED) e celle fotovoltaiche organiche (OPV), ha scatenato un'intensa attività di ricerca in questo campo. Sulla base dei recenti progressi nella tecnologia dei materiali e dei processi e del previsto sviluppo tecnologico futuro, gli esperti sono stati in grado di identificare le sfide chiave di questa tecnologia, per le quali sono necessari importanti sviluppi. La ricerca accademica ha compiuto grandi sforzi per aumentare le prestazioni dei dispositivi, ad esempio se guardiamo l’andamento negli anni della mobilità dei portatori di carica per gli OFET riportata in letteratura possiamo vedere che è aumentata di diversi ordini di grandezza negli ultimi decenni ma spesso sono state trascurate le altre caratteristiche richieste per lo sviluppo industriale di queste tecnologie. Tra le sfide chiave identificate, sono presenti costi e scalabilità. Queste sfide sono direttamente collegate alla tecnica di preparazione e lavorazione dei materiali, in particolare del materiale semiconduttore. In questo lavoro vengono presentati due approcci principali per lo sviluppo di materiali sostenibili per l'elettronica organica, applicati a diverse classi di semiconduttori organici (dichetopirrolopirroli (DPPs), isoindaci (IGs), benzotiadiazoli (BTs) e benzotienobenzotiofeni (BTBTs). Il primo approccio si basa sull’uso della reazione di arilazione diretta piuttosto che le reazioni di accoppiamento più classiche come le reazioni di Suzuki-Miyaura, Kumada e Stille. Il secondo approccio presentato è lo sviluppo di condizioni micellari per la sintesi di semiconduttori organici. Lo studio della reazione di arilazione diretta ha subito un rapido sviluppo negli ultimi anni e sta diventando un'alternativa sempre più valida alle tradizionali reazioni di cross-coupling. La reazione di accoppiamento tradizionali richiedono reagenti organometallici, che in particolare quando sono funzionalizzati, spesso non sono disponibili in commercio o sono relativamente costosi e la loro sintesi prevede l'uso di reagenti infiammabili (es. Butillitio), non stabili e / o altamente tossici (composti organici dello stagno). Pertanto, la reazione di arilazione diretta rappresenta una strategia sintetica più attraente dal punto di vista ambientale ed economico. In particolare il secondo capitolo riporta la sintesi di derivati del BTBT, originali e non, a partire dal BTBT non funzionalizzato per arilazione diretta. Nel capitolo 4 è riportato uno studio sull'ottimizzazione delle condizioni di policondensazione per arilazione diretta per lo sviluppo di un nuovo copolimero a base di dianidride naftalentetracarbossilica per l'applicazione in OFET. Il secondo approccio sviluppato per la sintesi di semiconduttori organici discusso nei capitoli 3 e 4 è la catalisi micellare. Le reazioni micellari sono un argomento ben consolidato nella moderna sintesi organica, nonostante ciò nel campo dei semiconduttori organci gli esempi sono ancora limitati. L'uso della catalisi micellare per semiconduttori organici non è banale infatti solitamente si tratta di molecole fortemente funzionalizzate, altamente cristalline. Nelle diverse sezioni del capitolo 3 e 4 sono esposte diverse strategie sviluppate per l'applicazione della catalisi micellare alle sintesi dei semiconduttori organici. In particolare il capitolo 3 si concentra sulla preparazione dei materiali molecolari a base di derivati del BT e BTBT, invece il capitolo 4 riporta l'ottimizzazione di una preparazione di F8BT, noto semiconduttore organico commerciale, in condizioni micellari. The synthesis and characterization of organic semiconductors (OS) has been a focal research field in the last two decades. Their potential application to large-area and flexible electronic devices, such as organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs), and organic photovoltaics (OPVs), has sparked intensive research in this field. Organic printed electronics (OPE) is based on the combination of new materials and cost-effective, large area production processes that open up new fields of application. Thinness, light weight, flexibility and potential environmental sustainability are key potential advantages of organic electronics. In fact, several high-tech companies have significantly invested in cheap and high-performance organic-electronic devices, a billion-dollar market that is expected to grow rapidly. Based on the recent progress in materials and process technology and the expected future technology development, the experts were able to identified that key challenges called “Red Brick Walls”, for which major breakthroughs are needed. Academic research has done big effort to increase devices performances, indeed for example if we look charge career mobility for OFET or power efficiency conversion for OPV reported in literature by years we can see that have been increase of different order of magnitude during the last decades but often overlooked the other features required for the OPE industrial development. Indeed among the key challenge identified cost and scalability are present. These challenges are directly linked with the preparation and processing technique of the materials, in particular of the organic semiconductor materials. Here are presented two main approaches in order to development of sustainable materials for organic electronics applied to different OS classes (Diketopyrrolopyrroles (DPPs), Isoindigoes (IGs), Benzothiadiazoles (BTs) and Benzothienobenzothiophenes (BTBTs)): the use of the direct arylation reaction in place of the more classical reactions of Suzuki-Miyaura, Kumada and Stille cross-coupling reactions and the develop of micellar conditions for organic OS synthesis.In particular the second chapter are reported the synthesis of, original and not, [1]benzothieno[3,2-b][1]benzothiophene (BTBT) derivatives, a class of very promising p-materials for OFET, starting from parent BTBT by direct arylation . These are the first examples of late stage functionalization of BTBT scaffold by direct arylation, In chapter 4 is reported a study of optimization of direct arylation polycondensation condition for the develop of a new Naphthalenetetracarboxylic dianhydride-based copolymer for OFET application. The second approach developed for organic OS synthesis reported in chapter 3 and 4 is the micellar catalysis. Micellar reactions are a well established topic in modern organic synthesis, indeed the numbers of reactions reported in literature to date in micellar condition is quite impressive despite this in the field of organic OS the examples are still limited. The use of micellar catalysis for OS material in not trivial indeed organic OS are usually heavily functionalized molecules, highly crystalline and they can interfere with surfactant micellization these lead to low conversion. In the different sections of chapter 3 and 4 are exposed several strategies developed for the application of micellar catalysis to the OS synthesis.

In this work we report on fully operational sub-micrometric low voltage OFETs by using graphene as the source-drain electrodes pair and a high- κ ultra-thin dielectric in a local gate architecture. The impact of the graphene electrodes on the miniaturization of the organic devices has been assessed, with particular attention to the influence of the contact resistances as well as the parasitic overlap gate capacitance on the device bandwidth. By the use of a modified Transmission-Line-Method, contact resistances have been analyzed as function of the applied voltages, revealing characteristic functional trends that follow the doping state of graphene electrodes. Through impedance spectroscopy of the electrodes, cut-off frequencies as high as 105 Hz have been estimated, highlighting the peculiar role of quantum capacitance of graphene in such architectures.