Photovoltaics from soluble small molecules Lloyd, Matthew T.; Anthony, John E.; Malliaras, George G.
Materials today (Kidlington, England),
11/2007, Volume:
10, Issue:
11
Journal Article
Peer reviewed
Open access
Solution-processable small molecules have attractive features for application in photovoltaic cells. They offer the facile processing associated with polymers, yet are easier to synthesize and ...purify, are monodisperse, and typically show higher charge carrier mobilities. Recent progress in solution-processable small molecule blends has yielded photovoltaic cells with efficiencies exceeding 1%. This article reviews progress in this nascent field and discusses the requirements imposed by the need for charge separation within an interpenetrating network, energy level tuning for light absorption and voltage output, and processing techniques to achieve phase separation on excitonic length scales. Design criteria for next-generation materials are provided.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In recent years, organic electrochemical transistors (OECTs) have emerged as attractive devices for a variety of applications, particularly in the area of sensing. While the electrical ...characteristics of OECTs are analogous to those of conventional organic field effect transistors, appropriate models for OECTs have not yet been developed. In particular, little is known about the transient characteristics of OECTs, which are determined by a complex interplay between ionic and electronic motion. In this paper a simple model is presented that reproduces the steady‐state and transient response of OECTs by considering these devices in terms of an ionic and an electronic circuit. A simple analytical expression is derived that can be used to fit steady‐state OECT characteristics. For the transient regime, comparison with experimental data allowed an estimation of the hole mobility in poly(3,4‐ethylenedioxythiophene) doped with poly(styrene sulfonate). This work paves the way for rational optimization of OECTs.
A model for the steady‐state and transient behavior of organic electrochemical transistors (see figure) is developed. Comparison with experimental results allows an estimate of the hole mobility in PEDOT:PSS, which was found to be in the range of 10‐2–10‐3 cm2 / V s. The model enables the rational design of design of devices based on electrochemical transistors, including sensors.
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Conducting polymers, which can simultaneously support transport of ions in addition to electronic charges, form the basis for electrochemical devices that transduce ionic signals into electronic ...signals, and vice versa . Understanding and controlling mixed conduction is, however, challenging due to a lack of methodology to simultaneously probe ion (and hole) injection and/or transport, as well as the morphology and film microstructure through which ions traverse. Here, we present a straightforward technique that takes advantage of the electrochromic nature of conducting polymers in order to deduce links between conjugated polymer aggregates, molecular (dis)order, and ion penetration. The morphology of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films and, subsequently, ionic transport are tuned by the addition of the co-solvent ethylene glycol in the dispersions. Time lapse UV-VIS spectra of these films, acquired during their redox-cycle, provide valuable insight into the pathways of ions inside the conducting polymer and the nature of aggregates therein. The structure–property relationships gained using such techniques promise to guide the design of polymeric active materials for devices that rely on mixed conduction.
Fast bacterial detection and identification is a crucial challenge in order to improve our antibiotics use and reduce the antimicrobial resistance. Electroanalysis of biological fluids is cheap and ...can be done in situ but the electrode material needs to be perfectly chosen. We previously studied electrochemical signature of Pseudomonas aeruginosa's secretome, thanks to glassy carbon electrode. Some conductive polymers are particularly efficient for biological use because of their antifouling properties, biocompatibility and way of processing. In this paper, we described the fabrication, characterization and utilisation of PEDOT:PSS film to detect and identify Pseudomonas aeruginosa through three of its secreted molecules: pyocyanin, Pseudomonas quinolone PQS and 2'-aminoacetophenone. The electrochemical responses, clearly amplified by PEDOT:PSS, can be used to identify these bacteria quickly and efficiently.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Electrowetting on Immersed Conducting Hydrogel Duc, Caroline; Vlandas, Alexis; Malliaras, George G ...
The journal of physical chemistry. B,
10/2017, Volume:
121, Issue:
42
Journal Article
Peer reviewed
Conducting polymers demonstrate an interesting ability to change their wettability at ultralow voltage (<1 V). While the conducting hydrogel poly(3,4-ethylenedioxythiophene) polystyrenesulfonate ...(PEDOT:PSS) is increasingly used as an interface with biology partly thanks to its mechanical properties, little is known about the electrical control of its wettability. We rely on the captive bubble technique to study this hydrogel property under relevant conditions (fully immerged). We here report that the wettability variations of PEDOT:PSS are driven by an electrowetting phenomenon in contrast to other conducting polymers which are thought to undergo wettability changes due to oxido-reduction reactions. In addition, we propose a modified electrowetting model to describe the wettability variations of PEDOT:PSS in aqueous solution under ultralow voltage and we show how these variations can be tuned in different ranges of contact angles (above or under 90°) by coating the PEDOT:PSS surface.
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IJS, KILJ, NUK, PNG, UL, UM
The integration of an organic electrochemical transistor with human barrier tissue cells provides a novel method for assessing toxicology of compounds in vitro. Minute variations in paracellular ...ionic flux induced by toxic compounds are measured in real time, with unprecedented temporal resolution and extreme sensitivity.
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Bacterial identification is of first importance in clinic nowadays. For few years, electrochemistry appears as a reliable route for characterizations outside of laboratories. Nowadays, researchers ...mainly focus on the opportunistic pathogen Pseudomonas aeruginosa because of its production of the Pyocyanin toxin which has an electrochemical case study behavior. Other P. aeruginosa secreted molecules are also studied in a lesser extent. This work deals with the systematic electrochemical characterizations in aprotic and protic solvents of 4 main metabolites of this bacterium in the view of multispecies detection of P. aeruginosa. We report here the behavior of the 2‐Heptyl‐4(1H)‐quinolone (HHQ), Pseudomonas Quinolone Signal (PQS), Pyocyanin (PYO) and the 2′aminoacetophenone (2‐AA). All the mentioned species are clearly visible by using electrochemical techniques (cyclic and square wave voltammetries). The 2 most suitable species for electrochemical detection appear to be PQS and PYO because of their detection at low potential.
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By employing benign process solvents and specially tailored photopolymers, organic electronic materials can be lithographically patterned. Furthermore, because the process is acid stable, this is an ...ideal candidate for patterning acidic PEDOT:PSS, an important material for organic electronics. Fabrication of a multilayer OTFT demonstrates the potential of this orthogonal patterning process.
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Organic semiconductors can be employed as the active layer in accumulation mode organic electrochemical transistors (OECTs), where redox stability in aqueous electrolytes is important for long‐term ...recordings of biological events. It is observed that alkoxy‐benzo1,2‐b:4,5‐b′dithiophene (BDT) copolymers can be extremely unstable when they are oxidized in aqueous solutions. The redox stability of these copolymers can be improved by molecular design of the copolymer where it is observed that the electron rich comonomer 3,3′‐dimethoxy‐2,2′‐bithiophene (MeOT2) lowers the oxidation potential and also stabilizes positive charges through delocalization and resonance effects. For copolymers where the comonomers do not have the same ability to stabilize positive charges, irreversible redox reactions are observed with the formation of quinone structures, being detrimental to performance of the materials in OECTs. Charge distribution along the copolymer from density functional theory calculations is seen to be an important factor in the stability of the charged copolymer. As a result of the stabilizing effect of the comonomer, a highly stable OECT performance is observed with transconductances in the mS range. The analysis of the decomposition pathway also raises questions about the general stability of the alkoxy‐BDT unit, which is heavily used in donor–acceptor copolymers in the field of photovoltaics.
The redox‐stability of benzodithiophene copolymers is analyzed where it is found that copolymers with large ionization potentials (IPs) degrade during electrochemical oxidation in aqueous electrolytes while copolymers with a small IP can be charged reversibly. The degradation product is identified to be a quinone structure which has a significant impact on the performance of the copolymers in electronic devices.
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