Browsing by Author "Tao, Yu-Tai"

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Accessing pi-expanded heterocyclics beyond dibenzothiophene: Syntheses and properties of phenanthrothiophenes
(1970-01-01)
Venkateswarlu, Samala
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Prakoso, Suhendro Purbo
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Kumar, Sushil
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Tao, Yu-Tai
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應用化學系
A series of phenanthrothiophenes are designed and synthesized from polyarylthiophenes through regioselective Scholl reactions in one step using iron chloride as catalyst. The molecular structures of these heteroarenes displayed multiple twisted fjords, which perturb the shapes of the polycyclic frameworks to pack in slipped to near-perfect face-to-face styles in parallel or antiparallel packings. Field-effect transistor devices using single crystals of 6,12-difluorodiphenanthro[9, 10-b:9 ', 10 ']thiophene gave a hole mobility of 0.22 cm(2) V-1 s(-1).
Benzophenanthrothiophenes: Syntheses, Crystal Structures, and Properties
(2019-09-06)
Venkateswarlu, Samala
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Prakoso, Suhendro Purbo
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Kumar, Sushil
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Kuo, Ming-Yu
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Tao, Yu-Tai
A new class of polycyclic heteroarenes based on benzo[3,4]phenanthro[1,2-b]benzo[3,4]phenanthro[2,1-d]thiophene (BPBPT) was prepared from polyaryl thiophenes via regioselective Scholl reactions. The molecular frameworks of these compounds exhibited twisted bridges and near-cofacial packing motifs with oppositely or parallel pi-stacked structures depending on the substituents on the periphery. Theoretical calculation of electronic coupling and charge mobility was carried out on the basis of the single-crystal structures. Single crystals of selected benzophenanthrothiophenes were used in p-channel field-effect transistor device fabrication, from which the highest mobility was measured as 2.03 cm(2) V-1 s(-1) from Flu-BPBPT.
Compact TiO2 films with sandwiched Ag nanoparticles as electron-collecting layer in planar type perovskite solar cells: improvement in efficiency and stability
(2018-01-01)
Abate, Seid Yimer
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Wu, Wen-Ti
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Pola, Someshwar
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Tao, Yu-Tai
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應用化學系
Fabrication of perovskite solar cells (PSCs) in a simple way with high efficiency and stability remains a challenge. In this study, silver nanoparticles (Ag NPs) were sandwiched between two compact TiO2 layers through a facile process of spin-coating an ethanolic AgNO3 solution, followed by thermal annealing. The presence of Ag NPs in the electron-transporting layer of TiO2 improved the light input to the device, the morphology of the perovskite film prepared on top, and eliminated leakage current. Photoluminescence and electron mobility studies revealed that the incorporation of Ag NPs in the ETL of the planar PSC device facilitated the electron-hole separation and promoted charge extraction and transport from perovskite to ETL. Hysteresis-free devices with incorporated Ag NPs gave a high average short-circuit current density (J(sc)) of 22.91 +/- 0.39 mA cm(-2) and maximum power conversion efficiency of 17.25%. The devices also showed enhanced stability versus a control device without embedded Ag NPs. The possible reasons for the improvement are analyzed and discussed.
Concomitant tuning of metal work function and wetting property with mixed self-assembled monolayers
(2011-01-01)
Chen, Chun-Yu
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Wu, Kun-Yang
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Chao, Yu-Chiang
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Zan, Hsiao-Wen
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Meng, Hsin-Fei
The effect of the surface composition of a mixed self-assembled monolayer on the work function and wetting property of silver substrate are investigated with the mixtures of a fluorinated alkanethiol and a carboxyl-terminated alkanethiol of various chain lengths. The work function of silver can be tuned from 4.3 to 5.3 eV by changing the mixing ratio while the wetting property can be modulated by adjust the relative chain length of the fluorinated thiol and the carboxyl-terminated thiol. Thus solution-processed poly(para phenylene vinylene)-based polymer light-emitting diode was made possible with high efficiency of 6.7 cd/A and brightness of 40,000 cd/m(2). (C) 2010 Elsevier B. V. All rights reserved.
High output current in vertical polymer space-charge-limited transistor induced by self-assembled monolayer
(2012-08-27)
Zan, Hsiao-Wen
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Hsu, Yuan-Hsuan
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Meng, Hsin-Fei
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Huang, Chian-Hao
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Tao, Yu-Tai
We present a promising solution-processed vertical transistor which exhibits high output current, high on/off current ratio, and low operation voltage. Numerous poly(3-hexylthiophene) vertical channels are embedded in vertical nanometer pores. Treating the sidewalls of pores by self-assemble monolayer with long alkyl chains enhances the pore-filling and inter-chain order of poly (3-hexylthiophene). The channel current is therefore greatly increased. A grid metal inside the porous template controls the channel potential profile to turn on and turn off the vertical transistor. Finally, the transistor delivers an output current density as 50-110 mA/cm(2) at 2V with an on/off current ratio larger than 10 000. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4748284]
n-Type Thin-Film Transistors Based on Diketopyrrolopyrrole Derivatives: Role of Siloxane Side Chains and Electron-Withdrawing Substituents
(2020-01-08)
Prakoso, Suhendro Purbo
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Kumar, Sushil
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Wu, San-Lien
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Ciou, Guan-Ting
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Ke, Yao-Jin
The physical properties, packing, morphology, and semiconducting performance of a planar pi-conjugated system can be effectively modified by introducing side chains and substituent groups, both of which can be complementary to the pi framework in changing the intermolecular association, frontier molecular orbital energy, optical band gap, and others. We herein show that installation of end-capped electron-withdrawing groups (EWGs), such as dicyanovinyl (-DCV), 3-ethylrhodanine (-RD), and 2-(3-oxo-indan-1-ylidene)-malononitrile (-INCN), together with siloxane side chains to the backbones of dithienyldiketopyrrolopyrrole (DPPT), such as DPPT-Si-DCV, DPPT-Si-RD, and DPPT-Si-INCN, can greatly improve its solubility, air stability, and film morphology to serve as an n-channel in thin-film transistor fabrication. The EWGs attached to the DPPT core narrowed the optical band gap (E-g(opt)) and changed the highest occupied molecular orbital and the lowest unoccupied molecular orbital energies (E-HOMO and E-LUMO), making them suitable for n-channel field-effect transistor (FET) applications. The benefits of introducing siloxane side chains to the DPPT core include enhanced solubility, low crystallization barrier, enantiotropic phase behavior, and much improved FET performance. The DPPT-Si-INCN film displayed low-lying HOMO (-5.82 eV) and LUMO (-4.60 eV) energy levels and an optical band gap as low as 1.22 eV, all of which suggest that this derivative can be quite resistant toward aerial oxidation. Thin films of these derivatives were prepared by the solution-shear method. A comparison of the solution-sheared films indicated that the molecular packing motif of DPPT-Si-INCN film was somehow different from that of DPPT-Si-DCV and DPPT-Si-RD, in which the pi-pi stacking tended to align orthogonally to the shearing direction. This specific pi-pi stacking alignment could have an impact on the electron mobility (mu(e)) values in transistors based on the solution-sheared films.
New Helicene-Type Hole-Transporting Molecules for High-Performance and Durable Perovskite Solar Cells
(2018-12-05)
Lin, Yeo-Sin
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Abate, Seid Yimer
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Lai, Kuan-Wen
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Chu, Chih-Wei
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Lin, Yan-Duo
Three azahelicene derivatives with electron-rich bis(4-methoxyphenyl)amino or bis(p-methoxyphenyl)aminophenyl groups at the terminals were deliberately designed, synthesized, and characterized as hole-transporting materials (HTMs) for perovskite solar cells (PSCs). Optical and thermal properties, energy level alignments, film morphologies, hole extraction ability, and hole mobility were studied in detail. PSCs using the newly synthesized molecules as HTMs were fabricated. A maximum power conversion efficiency (PCE) of 17.34% was observed for the bis(p-methoxyphenyl)amino-substituted derivative (SY1) and 16.10% for the bis(p-methoxyphenyeaminophenyl-substituted derivative (SY2). Longer-chain substituent such as hexyloxy group greatly diminishes the efficiency. In addition, the dopant-free devices fabricated with SY1 as the HTM shows an average PCE of 12.13%, which is significantly higher than that of spiro-OMeTAD (7.61%). The ambient long-term stability test revealed that after 500 h, the devices prepared from SY1 and SY2 retained more than 96% of its initial performance, which is much improved than the reference device with standard spiro-OMeTAD as the HTM under the same conditions. Detailed material cost analysis reveals that the material cost for SY1 is less than 8% of that for spiro-OMeTAD. These results provide a useful direction for designing a new class of HTMs to prepare highly efficient and more durable PSCs.
Nonlinear Polyfused Aromatics with Extended pi-Conjugation from Phenanthrotriphenylene, Tetracene, and Pentacene: Syntheses, Crystal Packings, and Properties
(2018-10-05)
Kumar, Sushil
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Huang, Ding-Chi
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Venkateswarlu, Samala
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Tao, Yu-Tai
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應用化學系
New classes of nonlinear polyaromatics with extended conjugation at lateral and longitudinal directions from triphenylene, tetracene, and pentacene backbones are reported. These planar and twisted polyfused aromatics are obtained through specific and selective multifold Scholl reactions from predesigned polyaryls. These derivatives displayed shifted or perfect cofacial packing motifs. Single crystals of one derivative, phenanthro[9,10:b]triphenylene, were used as p-channel materials in fabricating transistor devices, which exhibited an average mobility of 0.38 cm(2) s(-1) and a maximum mobility reaching 1.15 cm(2) V-1 s(-1)
Novel self-assembled metallo-homopolymers and metallo-alt-copolymer containing terpyridyl zinc(II) moieties
(2006-12-12)
Chen, Yi-Yu
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Tao, Yu-Tai
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Lin, Hong-Cheu
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材料科學與工程學系
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Department of Materials Science and Engineering
A series of novel terpyridyl Zn(II)-based metallo-polymers, including metallo-homopolymers and metallo-alt-copolymer, containing carbazole pendants attached to the C-9 position of fluorene by long alkyl spacers were constructed by self-assembled reaction. The integrated ratios of H-1 NMR reveal a facile result to distinguish the differences between metallo-homopolymers and copolymers. To further investigate these polymers, UV-vis and PL spectral titration experiments were also carried out by varying the molar ratios of zinc(II) ions to monomers. The photophysical properties of these polymers exhibited blue PL emissions (around 420 nm) with quantum yields of 11-23% (in DMF) and the PL results revealed that the formation of excimers were suppressed by the incorporation of carbazole pendant groups. In addition, the EL results showed green EL emissions ( around 550 nm) with turn-on voltages of 6.0-6.5 V, maximum efficiencies of 0.85-1.1 cd A(-1) (at 100 mA cm(-2)), and maximum luminances of 1704-2819 cd/m(2) (around 15 V), correspondingly.
Photodegradation of organic dyes and industrial wastewater in the presence of layer-type perovskite materials under visible light irradiation
(2018-08-01)
Gade, Ramesh
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Ahemed, Jakeer
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Yanapu, Kalyana Lakshmi
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Abate, Seid Yimer
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Tao, Yu-Tai
Layer-type perovskite materials based on A(I)A(II)Ti(2)O(6) (A(I )= Na or Ag or Cu and A(II) = La) system for the degradation of several organic dyes and industrial wastewater under visible-light irradiation are reported. The known perovskite material NaLaTi2O6 (NLTO) was prepared by a new sol-gel process. Ion-exchange of Na+ ions in NLTO with Ag(+ )or Cu2+ ion led to new perovskite AgLaTi2O6 (ALTO) and Cu-0.5 LaTi2O6 (CLTO) respectively. All the new materials were thoroughly characterized by using PXRD, FESEM, HRTEM, UV-vis DRS, IR, XPS and Solid State Photo-luminescence techniques. The new series of materials were utilized for the degradation of Congo Red dye, 4-chlorophenol and 4,4'-bis(2-sulfostyryl)biphenyl as reference pollutants, as well as industrial wastewater. The mineralization process of Congo Red was evaluated through mass spectrometry, which showed that after 60 min of irradiation, the dye degraded with all fragments disappeared. Degradation and mineralization of industrial wastewater was studied by using a newly designed photoreactor via a two-stage process. Mechanistic studies for the fast degradation of Congo Red and industrial wastewater were carried out in the presence of various scavengers. Finally, the photomineralized wastewater was evaluated by chemical oxygen demand (COD) test and the obtained value is close to the standard value. Highest efficiency of degradation was found for ALTO as the photocatalyst, followed by CLTO and then NLTO.
Polysubstituted Hexa-cata-hexabenzocoronenes: Syntheses, Characterization, and Their Potential as Semiconducting Materials in Transistor Applications
(2019-07-05)
Kumar, Sushil
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Pola, Someshwar
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Huang, Chih-Wei
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Islam, Md. Minarul
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Venkateswarlu, Samala
A series of tetra- and octa-substituted hexa-cata-hexabenzocoronenes (cata-HBCs) were synthesized from tetraryl olefins via iodine- and iron chloride-catalyzed oxidative cyclodehydrogenation reactions. The substitutions on the periphery of the parent HBC serve to modify the photophysical properties, highest occupied molecular orbital-lowest unoccupied molecular orbital gaps, and thermal stabilities of the respective derivatives. The crystal structures were determined to display multiple twists in the framework, resulting in different packing motifs depending on the position, type, and number of functional groups on the hexabenzocoronene framework. Nearly perfect co-facial packing to marginally or extensively shifted co-facial stacks were obtained due to substitution. The single crystals of parent HBC were used to fabricate single-crystal field-effect transistors, from which the highest p-channel mobility of 0.51 cm(2) V-1 s(-1) was measured. Thin-film transistors of selected HBCs were also prepared, and 0.61 cm(2) V-1 s(-1) was obtained for MeHBC-2. These results attest the potential of these materials as semiconducting materials.
Room-temperature-operated organic-based acetone gas sensor for breath analysis
(2018-05-01)
Chuang, Ming-Yen
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Lin, Yu-Ting
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Tung, Ting-Wei
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Chang, Liang-Yu
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Zan, Hsiao-Wen
The major merits of organic-based sensors include their low cost, room-temperature operation, and small size. However, their sensitivity and selectivity are concerning, especially in the application of breath analysis. In this work, organic-based sensors were developed based on cylindrical nano-pore structures, which enhanced the sensitivity down to ppb levels. The sensing performance was demonstrated both in pure nitrogen and ambient air. The sensor constructed with poly[(9,9-dioctylfluoreny1-2,7-diy1)-co-(4,41(N-(4-sec-butylphenyl)diphenylamine)] (TFB) exhibited a 5% sensing response to 300 ppb of acetone in ambient air. In addition, the sensor's response to other major breath components, including nitric oxide, ethanol, carbon dioxide, and ammonia, was also established. The results showed that the TFB sensor also exhibited a good response to ammonia. Therefore, a humidification tube was designed as an ammonia filter to improve selectivity. The concept of integrating a highly sensitive sensor with a customized sensing system shows promise for medical applications. (C) 2018 Elsevier B.V. All rights reserved.