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Application of rubrene air-gap transistors as sensitive MEMS physical sensors
摘要： Micro electromechanical systems (MEMS) made of organic materials have attracted efforts on development a new generation of physical, chemical and biological sensors, for which the electromechanical sensitivity is the current major concern. Here, we present an organic MEMS made of a rubrene single crystal air-gap transistor. Applying mechanical pressure on the semiconductor results in high variations of drain current: an unparalleled Gauge factor above 4000 has been measured experimentally. Such a high sensitivity is induced by the modulation of charge injection at the interface between the gold electrode and the rubrene semiconductor as an unusual transducing effect. Applying these devices to the detection of acoustic pressure shows that force down to 230 nN can be measured with a resolution of 40 nN. This study demonstrates that MEMS based on rubrene air-gap transistors constitute a step forward to the development of high performance flexible sensors.
关键词： crystal,charge injection,organic MEMS,pressure sensor,air-gap transistor,OFET,rubrene
更新于2025-09-23 15:21:21
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The reactivity of solid rubrene with potassium: competition between intercalation and molecular decomposition
摘要： We present the synthesis and characterization of the K+ intercalated rubrene (C42H28) phase, K2Rubrene (K2R) and identify the co-existence of amorphous and crystalline materials in samples where the crystalline component is phase pure. We suggest this is characteristic of many intercalated alkali metal-polyaromatic hydrocarbon (PAH) systems, including those for which superconductivity has been claimed. The systematic investigation of K-rubrene solid state reactions using both K and KH sources reveals complex competition between K intercalation and the decomposition of rubrene, producing three K-intercalated compounds, namely, K2R, K(RR*), and KxR? (where R* and R? are rubrene decomposition derivatives C42H26 and C30H20, respectively). K2R is obtained as the major phase over a wide composition range and is accompanied by the formation of amorphous by-products from the decomposition of rubrene. K(RR*) is synthesized as a single phase and KxR? is obtained only as a secondary phase to the majority K2R phase. The crystal structure of K2R was determined using high resolution powder X-ray diffraction, revealing that the structural rearrangement from pristine rubrene creates two large voids per rubrene within the molecular layers in which K+ is incorporated. K+ cations accommodated within the large voids interact strongly with the neighbouring rubrene via η6, η3 and η2 binding modes to the tetracene cores and the phenyl groups. This contrasts with other intercalated PAHs where only a single void per PAH is created and the intercalated K+ weakly interact with the host. The decomposition products of rubrene are also examined using solution NMR, highlighting the role of the breaking of C-CPhenyl bonds. For the crystalline decomposition derivative products K(RR*) and KxR?, a lack of definitive structural information with regards to R* and R? prevents the crystal structures being determined. The study illustrates the complexity in accessing solvent-free alkali metal salts of reduced PAH of the type claimed to afford superconductivity.
关键词： crystal structure,decomposition,rubrene,intercalation
更新于2025-09-23 15:21:21
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Evaluating intrinsic mobility from transient terahertz conductivity spectra of microcrystal samples of organic molecular semiconductors
摘要： In microcrystal samples of the prototypical organic molecular semiconductors rubrene and C10-DNTT (2,9-didecyl-dinaphtho[2,3-b:20,30-f]thieno[3,2-b]thiophene), we measured spectra of complex optical conductivity caused by photocarriers with optical-pump terahertz-probe spectroscopy. We analyzed the ~r xe T spectra using the Drude-Smith model and evaluated the DC mobility lDC, which includes extrinsic effects, and the intrinsic mobility lint. The resulting lDC and lint values are comparable to the mobility values obtained using transport measurements of polycrystalline and single-crystalline ?eld-effect transistors, respectively. This correspondence demonstrates that the intrinsic mobility values of organic molecular semiconductors can be evaluated from the measurements of microcrystal samples using transient terahertz spectroscopy.
关键词： mobility,C10-DNTT,organic molecular semiconductors,terahertz spectroscopy,rubrene
更新于2025-09-23 15:19:57
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Variations of the elastic modulus perpendicular to the surface of rubrene bilayer films
摘要： Investigations exploring the inherent mechanical properties of electronic materials have grown rapidly in recent years largely because they are important in developing flexible electronics, organic displays and sensors. However, our understanding of the mechanical properties of organic semiconductors with a thin-film form remains limited. We report herein on an investigation of the structures and related elastic moduli perpendicular to the surface of a rubrene thin film. A rubrene/Si(100) film typically has a cluster-type morphology mainly comprised of crystalline nanodomains within the film. We propose a structural bilayer model that can be used to explain the layered nature or characteristics of the rubrene films. As the film thickness is increased, the enhancement in elastic modulus can be attributed to the presence of a soft surface layer on a hard underlayer. Based on four-point probe measurements, the bilayered nature of such materials can be used to characterize their electrical resistive behavior while interfacial roughness is sensitive to the transport paths of conduction electrons. This information is valuable for future applications of organic semiconductors in flexible devices.
关键词： four-probe measurement,atomic force microscopy,rubrene,stress
更新于2025-09-19 17:15:36
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Triplet-triplet annihilation effects in rubrene/C60 OLEDs with electroluminescence turn-on breaking the thermodynamic limit
摘要： Recently, Engmann et al. experimentally and theoretically examined the higher-order effects in rubrene/C60 organic light-emitting diodes (OLEDs), claiming that triplet-triplet annihilation (TTA) is not responsible for the electroluminescence (EL) with extremely-low turn-on voltage (Voc). Instead, the evidence from the equivalent circuit fitting suggest that the direct band-to-band recombination can interpret the low voltage phenomena. However, at applied bias of about 1.0 V, the excitons prefer to form on the charge-transfer state between rubrene/C60 interface. Direct singlet formation on rubrene and direct band-to-band recombination seems impossible to be accountable for such low Voc.
关键词： thermodynamic limit,electroluminescence,rubrene/C60 OLEDs,triplet-triplet annihilation
更新于2025-09-19 17:13:59
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Monolayer rubrene functionalized graphene-based eletrochemiluminscence biosensor for serum cystatin C detection with immunorecognition-induced 3D DNA machine
摘要： Only surficial molecules of eletrochemiluminscent (ECL) nanomaterials are the most reactive species in the typical ECL reaction. Herein, monolayer rubrene was assembled on the surface of graphene sheet to obtain monolayer rubrene functionalized graphene composite (G/mRub) with strong ECL emission by maximizing the surficial rubrene molecules. Based on G/mRub as the strong ECL emitter, an ultrasensitive “on-off” biosensor was developed to detect cystatin C (Cys C) in human serum with the help of a novel immunorecognition-induced enzyme-free 3D DNA machine. Benefiting from the strong ECL emission of G/mRub and the efficient signal amplification of 3D DNA machine, the established biosensor achieved high sensitivity for Cys C detection with linear range from 1.0 fg mL-1 to 10 ng mL-1 and limit of detection down to 0.38 fg mL-1. In addition, this enzyme-free biosensing method was adopted to successfully detect the concentration of Cys C in human serum. Therefore, the G/mRub based ECL biosensor might provide a potential tool for protein detection in clinical diagnosis and a new avenue to prepare high-performance luminescent nanomaterials.
关键词： electrochemiluminescence,graphene,cystatin C,monolayer rubrene,3D DNA machine
更新于2025-09-04 15:30:14