Browsing by Author "Chen, Chin-Yi"

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Influences of Conjugation Length on Organic Field-Effect Transistor Performances and Thin Film Structures of Diketopyrrolopyrrole-Oligomers
(2018-03-14)
Huang, Yi-Fan
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Chang, Shu-Ting
;
Wu, Kuan-Yi
;
Wu, San-Lien
;
Ciou, Guan-Ting
Here, two diketopyrrolopyrrole (DPP)-based oligomers, DPP-4T and DPP-6T, are studied to reveal the influences of conjugation length on thin-film morphology and organic field-effect transistor (OFET) performances. PDMS-assisted crystallization in a solvent-annealing chamber is applied to prepare crystal arrays of DPP-4T and DPP-6T to optimize the quality of charge channels for OFET characterizations. To deliver insights into microstructure and morphology of thin films, a characterization procedure for determining molecular packing in thin film and crystallinity of the crystal arrays is presented via grazing incidence wide-angle X-ray scattering, electron diffraction, and lattice simulation software package (Cerius2). With the lattice parameters derived from analyses of grazing incidence wide-angle X-ray scattering (GIWAXS) and electron diffraction (ED), the lattice modeling results indicate that the inferior organic field-effect transistor (OFET) performances of DPP-6T are attributed to longer pi-stacking distance. Also, less-ordered molecular arrangement and lower continuity of crystalline domains, both of which are revealed from crystallinity results, lead to lower mobility of DPP-6T. In this case, longer conjugated backbones with more conformational degrees of freedom thus cause inherent crystal defects during the crystal growth process, despite the potential to enhance intermolecular pi-orbital overlap. Therefore, to achieve better OFET performance, suitable backbone length makes conjugated oligomers give high intermolecular pi-orbital overlap and low density of structural disorder, which are the priorities for constructing good charge channel.
Influences of Structural Modification of S,N-Hexacenes on the Morphology and OFET Characteristics
(2019-06-19)
Huang, Yi-Fan
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Wang, Chun-Kai
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Lai, Bo-Han
;
Chung, Chin-Lung
;
Chen, Chin-Yi
Although chemical modifications on conjugated molecules are widely applied for the purpose of improving processability and device performances, the effect of the modification was far less investigated. Here, five S,N-hexacenes are studied to reveal the influences of (1) the lateral alkyl chain, (2) the terminal group (thiophene vs benzene), and (3) the end capping phenyl group of the hexacenes on the morphology and organic field-effect transistor (OFET) performances. Crystal arrays of the hexacenes were prepared via polydimethylsiloxane (PDMS)-assisted crystallization (PAC) prior to morphological and OFET characterizations. The lattice structures and crystal quality of the hexacenes were evaluated by microscopy and diffraction techniques including single-crystal diffractometer, electron diffraction, and grazing incidence wide-angle X-ray scattering. The systematic analyses led to the following conclusions: (1) the bulkier alkyl side chain assists to form more densely packed crystals with less structural defects; (2) the terminal thiophene rings bring about higher-lying E-HOMO, more ordered phase, and crystal orientation, whereas the terminal benzene rings deteriorate the structural order of the active layer and result in the liquid crystal phase; and (3) the phenyl end caps ameliorate the morphological order, intermolecular overlapping, thermal stability and elevate E-HOMO. Thus, EH-DTPTt-Ph delivers the highest mu(h), contributing to high-lying E-HOMO, well-oriented crystal array with a longer correlation length, and suitable lattice orientation. This systematic research provides the aspects about the effects of the functionalized S,N-hexacenes on the morphology and OFET characteristics, which is anticipated to be useful for the molecular design of heteroacenes.
Nonlinear Deterministic Frontier Model Using Genetic Programming
(2009)
Chen, Chin-Yi
;
Huang, Jih-Jeng
;
Tzeng, Gwo-Hshiung
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科技管理研究所
;
Institute of Management of Technology
In economics, several parametric regression-based models have been proposed to measure the technical efficiency of decision making units (DMUs). However, the problem of misspecification restricts the use of these methods. In this paper, symbolic regression is employed to obtain the approximate optimal production function automatically using genetic programming (GP). Monte Carlo simulation is used to compare the performance of data envelopment analysis (DEA), deterministic frontier analysis (DFA) and GP-based DFA with respect to three different production functions and sample sizes. The simulated results indicated that the proposed method has better performance than that of others with respect to nonlinear production functions.
Polymorphic Behavior of Perylene and Its Influences on OFET Performances
(2018-07-19)
Hsieh, Chou-Ting
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Chen, Chin-Yi
;
Lin, Heng-Yi
;
Yang, Cheng-Jui
;
Chen, Tzu-Jung
Among the polycyclic aromatic hydrocarbons, although perylene is commercially available and possesses higher solubility and stability than the others, its thin-film structures and organic field-effect transistor (OFET) performances have been rarely explored. To understand its potential as an active material in OFETs, the polymorphic behaviors, packing structures, and OFET characteristics of perylene were carefully examined. The well-oriented crystal arrays of perylene prepared via droplet-pinned crystallization delivered the highest hole mobility among the reported perylene OFETs. Fluorescence microscope, electron diffraction, and lattice modeling results confirm the polymorphic behavior of perylene in the solution-processed crystal arrays and its influences on the OFET performances. The concentration-sensitive and temperature-sensitive polymorphic behavior of perylene make processing conditions crucial in the preparation of pure-phase crystal arrays. The results show the great potential of perylene as an active material in low-cost and high-performance OFETs. Moreover, the knowledge regarding the polymorphic behavior of perylene provides opportunity for the further optimization of perylene-based OFETs.