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Asymmetric Pentacenes for Solution-Processed Organic Field-Effect Transistors
摘要： Background: Symmetrically substituted pentacenes have been traditionally used as semiconductors for solution-processed p-channel Organic Field Effect Transistors (OFETs). The aims of this paper are to introduce asymmetrically substituted pentacenes in the active layer and to examine the impact of the polyaromaticity of the pendant groups on the device characteristics. Methods: Research and online content related to asymmetrically substituted pentacenes is reviewed, the synthesis of the different pentacenes is described and the procedure used to introduce these semiconductors in devices is detailed. Comparison with a reference material is provided. Results: Extension of the polyaromaticity of the pendant group of pentacene greatly contributes to enhance the device performances. Impact of the pendant group on the morphology of the active layer is evidenced by the roughness decreasing with the increase of aromatic ring in the substituent. Conclusion: We demonstrate the extension of the π-conjugation of the aromatic end-group to drastically impact both ON/OFF ratio and charge carrier mobilities, mainly due to various degree of crystal formation characteristics in the film. Best results were obtained with the most extended one, namely the anthracene moiety which showed a mobility comparable to that of the benchmark TIPS-pentacene with OFETs that used hexamethyldisilazane as the gate dielectric passivation layer.
关键词： solution-process,semiconductor,organic materials,OFET,Mobility,TIPS-pentacene
更新于2025-09-23 15:23:52
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Enhanced charge injection in 6, 13-bis(triisopropylsilylethylnyl)-pentacene field-effect transistors with a rhenium oxide buffer layer
摘要： We introduce a transition metal oxide, rhenium trioxide (ReO3), as a charge injection buffer layer for 6,13-bis(triisopropylsilylethylnyl)-pentacene (TIPS-pentacene) field-effect transistors (FETs). By inserting a ReO3 layer, a large energy barrier between silver source electrode and TIPS-pentacene layer was significantly reduced. While the TIPS-pentacene FETs showed low hole mobility (μh) of 0.25 cm2V?1s?1 and large threshold voltage (VTH) of ?25 V due to large contact resistance (RC) of 155 kΩ·cm, the TIPs-pentacene FETs with ReO3 decreased RC as low as 28 kΩ·cm. Thus, we can improve μh two times bigger (~ 0.46 cm2V?1s?1) and reduce VTH around 0 V. Together with these improved electrical characteristics, the TIPS-pentacene with ReO3 shows much stable operation under gate voltage bias stress condition. The shift of VTH and degradation of μh which were shown in the TIPS-pentacene FET without ReO3 is suppressed in the TIPS-pentacene FETs with ReO3 under both positive and negative bias condition.
关键词： ReO3,transistors,TIPS-pentacene,electrical property,thin-film,contact resistance,organic
更新于2025-09-19 17:15:36
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Conjugated Polymer Controlled Morphology and Charge Transport of Small-Molecule Organic Semiconductors
摘要： In this study, we report an effective approach to tune the crystallization, microstructure and charge transport of solution-processed organic semiconductors by blending with a conjugated polymer additive poly(3-hexylthiophene) (P3HT). When 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) was used as a model semiconductor material to mix with different amount of P3HT, their intermolecular interactions led to distinctive TIPS pentacene film morphologies, including randomly-oriented crystal ribbons, elongated needles with enhanced long-range order, and grass-like curved microwires with interlinkages. Each type of morphology was found to further correlate to considerably different charge transport and device performance. As compared to pristine TIPS pentacene devices, bottom-gate, top-contact OTFTs with 2% in weight P3HT additive showed a 2-fold and 5-fold improvement of average field-effect mobility and performance consistency (defined as the ratio of average mobility to the standard deviation), respectively. The improvement in transistor electrical performance can be attributed to the combined effect of enhanced crystal orientation and uniformity, as well as increased areal coverage. This work can be applied beyond the particular example demonstrated in this study and to tune the charge transport of other small-molecule organic semiconductors in general.
关键词： OTFTs,TIPS pentacene,organic semiconductors,film morphology,P3HT,charge transport,conjugated polymer
更新于2025-09-19 17:13:59
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Boosting Direct X-Ray Detection in Organic Thin Films by Small Molecules Tailoring
摘要： The attention focused on the application of organic electronics for the detection of ionizing radiation is rapidly growing among the international scientific community, due to the great potential of organic technology to enable large-area conformable sensor panels. However, high-energy photon absorption is challenging as organic materials are constituted of atoms with low atomic numbers. Here it is reported how, by synthesizing new solution-processable organic molecules derived from 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) and 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene, with Ge-substitution in place of the Si atoms to increase the material atomic number, it is possible to boost the X-ray detection performance of organic thin films on flexible plastic substrates. Bis(triisopropylgermylethynyl)-pentacene based flexible organic thin film transistors show high electrical performance with higher mobility (0.4 cm2 V?1 s?1) and enhanced X-ray sensitivity, up to 9.0 × 105 μC Gy?1 cm?3, with respect to TIPS-pentacene-based detectors. Moreover, similar results are obtained for 5,11-bis(triethylgermylethynyl)anthradithiophene devices, confirming that the proposed strategy, that is, increasing the atomic number of organic molecules by chemical tailoring to improve X-ray sensitivity, can be generalized to organic thin film detectors, combining high X-ray absorption, mechanical flexibility, and large-area processing.
关键词： organic X-ray detectors,thin film transistors,TIPS-pentacene,TIPGe-pentacene
更新于2025-09-09 09:28:46
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Is Vibrational Coherence a Byproduct of Singlet Exciton Fission?
摘要： A phenomenological wavefunction-based model of vibrationally coherent absorption modulation is proposed and applied to reproduce the triplet-triplet absorption spectra of bis-triisopropylsilylethynyl (TIPS)-pentacene, with the objective of testing whether the singlet fission process in that system spontaneously generates coherent vibrational packets, as recently suggested for TIPS-tetracene. The model is parametrized by a complete set of Franck-Condon parameters obtained from methodologically consistent DFT calculations for all relevant normal modes in all relevant electronic states. The results strongly depend on inhomogeneous broadening of absorption bands, which is explicitly included. They very well agree with the recently published experimental coherence spectra of the pertinent system, validating our underlying principal assumption that the singlet fission process, which generates the observed triplet states, is neutral with respect to vibrational coherences. Experimental confirmation of this interpretational posit demonstrates that in the pentacene derivative, apparently in contrast to the case of its tetracene analogue, fission is not a source of vibrational coherence. Our finding suggests that although the singlet fission process may possibly in individual cases induce vibrational coherence, this feature is not a constitutive characteristic of the fission phenomenon.
关键词： DFT calculations,singlet exciton fission,Franck-Condon parameters,TIPS-pentacene,vibrational coherence
更新于2025-09-04 15:30:14