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Stimuli-responsive polymer as gate dielectric for organic transistor sensors
(2020-10-01)
Rullyani, Cut
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Singh, Mriganka
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Li, Sheng-Han
;
Sung, Chao-Feng
;
Lin, Hong-Cheu
Temperature is a characteristic often correlated with environmental and health issues. This paper presents an organic thin film transistor (OTFT) based temperature sensor having a detection range of 30-45 degrees C, which, therefore, encompasses the human body temperature. The OTFT sensor featured thermosensitive poly(N-iso-propylacrylamide) (PNIPAM) and pentacene as the gate dielectric and semiconductor, respectively. The PNIPAM film possessed a dielectric constant of 4.2 with very low leakage current density. The OTFT exhibited high electrical performance, with a hole mobility (mu) of 0.90 +/- 0.04 cm(2) V-1 s(-1), a threshold voltage (V-th) of -15.4 +/- 1.16 V, and an on/off ratio of 10(4). Significant changes in the drain current and the values of V-th and mu occurred when the temperature of the device was varied within the range 30-45 degrees C at an interval of 0.5 degrees C. The operating principle for this temperature sensor was based on the structural transformation of the PNIPAM dielectric and the enhanced charge transport of the pentacene semiconductor upon varying the temperature. Flexible OTFTs fabricated on polyethylene terephthalate substrate displayed hole mobilities as high as 0.39 +/- 0.01 cm(2) V-1 s(-1), values of V-th of 18.6 +/- 0.45, and on/off ratios of 10(2), and were workable for over 100 bending cycles.
Asymmetric Benzotrithiophene-Based Hole Transporting Materials Provide High-Efficiency Perovskite Solar Cells
(2020-07-01)
Budiawan, Widhya
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Lai, Kuan-Wen
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Karuppuswamy, Priyadharsini
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Jadhav, Tushar Sanjay
;
Lu, Yen-An
In this study, we synthesized a series of small-molecule benzotrithiophenes (BTTs) and used them as hole transporting materials (HTMs) in perovskite solar cells (PSCs). The asymmetric benzo[2,1-b:-3,4-b':5,6-b"]trithiophene unit was used as the central core to which were appended various donor groups, namely, carbazole (BTT-CB), thieno thiophene (BTT-FT), triphenylamine (BTT-TPA), and bithiophene (BTT-TT). The extended aromatic core in the asymmetric BTT provided full planarity, thereby favoring intermolecular pi-stacking and charge transport. The physical, optical, and electrical properties of these small-molecule HTMs are reported herein. BTT-TT displayed good crystallinity and superior hole mobility, when compared with those of the other three HTMs, and formed smooth and uniform surfaces when covering the perovskite active layer. Accordingly, among the devices prepared in this study, a PSC incorporating BTT-TT as the HTM achieved the highest power conversion efficiency (18.58%). Moreover, this BTT-TT-containing device exhibited good stability after storage for more than 700 h. Thus, asymmetric BTTs are promising candidate materials for use as small-molecule HTMs in PSCs.
Circular Polarized Emission of Tungsten Diselenide (WSe2) Atomic Layers with Plasmonic Metasurface
(2018-01-01)
Lin, Hsiang-Ting
;
Chang, Chiao-Yun
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Cheng, Pi-Ju
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Li, Ming-Yang
;
Cheng, Chia-Chin
A circularly polarized light source with ultrathin geometry were demonstrated by integrating the WSe2 atomic layers with plasmonic chiral metasurfaces. The intrinsic chiral emission of WSe2 was manipulated by chiral metasurfaces to achieve emission circular dichroism more than 25%.
Enhanced Organic Solar Cell Performance by Lateral Side Chain Engineering on Benzodithiophene-Based Small Molecules
(2018-08-01)
Patra, Dhananjaya
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Budiawan, Widhya
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Huang, Tzu-Yen
;
Wei, Kung-Hwa
;
Wang, Pen-Cheng
The three novel acceptor-donor-acceptor (A-D-A) conjugated small molecules were synthesized, each featuring a benzodithiophene (BDT) core presenting lateral flexible side chains: TB-BDT6T substituted with 2-ethynyl-5-octylthiophene, TS-BDT6T substituted with 2-(octylthio)-thiophene, and TT-BDT6T substituted with 2-(2-ethylhexyl)-thieno[3,2-b]thiophene groups. The lateral incorporation of functionalized pi-conjugated flexible side chains, without altering the end-capped acceptor (cyanoacetate) moieties, amended the optoelectronic properties of these BDT-based small molecules. X-ray diffraction spectroscopy revealed that these small molecules possess high crystallinity; moreover, the optimized blend film morphologies, recorded using atomic force microscopy, revealed miscibility with PC61BM, and turn out nanoscale phase separations. The energy levels of the highest occupied and lowest unoccupied molecular orbitals of these small molecules were allowed, leading to high open-circuit voltages (V-oc) for their solar cell devices. The bulk heterojunction small-molecule solar cell based on TT-BDT6T:PC61BM blend presented the highest power conversion efficiency (5.80%) with a high value of V-oc of 0.98 V, a short circuit density of 9.49 mA cm(-2), and a fill factor of 62.44% under AM 1.5G irradiation (100 mW cm(-2)).
Pyrene-SH functionalized OTFT for detection of Hg2+ ions in aquatic environments
(2019-06-01)
Rullyani, Cut
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Shellaiah, Muthaiah
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Ramesh, Mohan
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Lin, Hong-Cheu
;
Chu, Chih-Wei
Mercury ion (Hg2+) sensor based on bottom gate top contact organic thin film transistor (OTFT) was fabricated. The OTFT channel area was functionalized with pyrene that contain thiol group, which has strong binding affinity toward Hg2+ ion. The OTFT sensor exhibited a charge mobility of 0.28 cm(2) V-1 s(-1), a threshold voltage of -22.3 V and on-to-off ratio 10(3). The sensor shows high selectivity to Hg2+ ion over other two valence metal ions. OTFT sensor exhibited high sensitivity to Hg2+ ion, indicated by increasing of drain current after exposed to different concentration of Hg2+ ion ranging from 1 mM to 0.01 mu M. Moreover, the OTFT sensor capability for practical application was also demonstrated by sensing the present of 25 mu M of Hg2+ ion in tap, drinking and seawater samples.
Facile synthesis of composite tin oxide nanostructures for high-performance planar perovskite solar cells
(2019-06-01)
Singh, Mriganka
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Ng, Annie
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Ren, Zhiwei
;
Hu, Hanlin
;
Lin, Hong-Cheu
Metal oxide carrier transporting layers have been investigated widely in organic/inorganic lead halide perovskite solar cells (PSCs). Tin oxide (SnO2) is a promising alternative to the titanium dioxide commonly used in the electron transporting layer (ETL), due to its tunable carrier concentration, high electron mobility, amenability to low-temperature annealing processing, and large energy bandgap. In this study, a facile method was developed for the preparation of a room-temperature-processed SnO2 electron transporting material that provided a high-quality ETL, leading to PSCs displaying high power conversion efficiency (PCE) and stability. A novel physical ball milling method was first employed to prepare chemically pure ground SnO2 nanoparticles (G-SnO2), and a sol-gel process was used to prepare a compact SnO2 (C-SnO2) layer. The effects of various types of ETLs (C-SnO2, G-SnO2, composite G-SnO2/C-SnO2) on the performance of the PSCs are investigated. The composite SnO2 nanostructure formed a robust ETL having efficient carrier transport properties; accordingly, carrier recombination between the ETL and mixed perovskite was inhibited. PSCs incorporating C-SnO2, G-SnO2, and GSnO(2)/C-SnO2 as ETLs provided PCEs of 16.46, 17.92, and 21.09%, respectively. In addition to their high efficiency, the devices featuring the composite SnO2 (G-SnO2/C-SnO2) nanostructures possessed excellent long-term stability-they maintained 89% (with encapsulation) and 83% (without encapsulation) of their initial PCEs after 105 days ( > 2500 h) and 60 days ( > 1400 h), respectively, when stored under dry ambient air (20 +/- 5 RH %).
Dependence of channel thickness on the performance of In2O3 thin film transistors
(2008-05-07)
Dhananjay
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Cheng, Shiau-Shin
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Yang, Chuan-Yi
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Ou, Chun-Wei
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Chuang, You-Che
Bottom gate and top contact thin film transistors were fabricated using In2O3 thin films as active channel layers. Thin films of varying thicknesses in the range 5 - 20 nm were deposited on an SiO2 gate dielectric by the thermal evaporation process in the presence of high purity oxygen. The results of atomic force microscopy show that all the films exhibit dense grain distribution with a root-mean-square roughness in the range 0.6-8.0 nm. Irrespective of the thickness of the channel layer, the on/off ratio of the device is 10(4). The channel mobility and resistivity were found to be a strong function of the thickness of the active layer. The Levinson model was used to calculate the trap density and the grain boundary mobility. The low processing temperature shows the possibility of utilizing these devices on flexible substrates such as polymer substrates.
Complementary inverter circuits based on p-SnO2 and n-In2O3 thin film transistors
(2008-06-09)
Dhananjay
;
Chu, Chih-Wei
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Ou, Chun-Wei
;
Wu, Meng-Chyi
;
Ho, Zhong-Yo
Thin film transistors (TFTs) of indium oxide (In2O3) and tin oxide (SnO2) were fabricated on SiO2 gate dielectric using reactive evaporation process. Structural investigation of the films revealed that In2O3 films were polycrystalline in nature with preferred (222) orientation and SnO2 films exhibited amorphous nature. The x-ray photoelectric spectroscopy measurements suggest that SnO2 films were oxygen rich and presume mixed oxidation states of Sn, namely Sn2+ and Sn4+. While the In2O3 based TFTs possess n-type channel conduction, SnO2 based TFTs exhibited anomalous p-type conductivity. Integration of these n- and p-type devices resulted in complementary inverter with a gain of 11. (C) 2008 American Institute of Physics.
Mitigating Metal Dendrite Formation in Lithium-Sulfur Batteries via Morphology-Tunable Graphene Oxide Interfaces
(2019-01-16)
Chen, Yu-Ting
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Abbas, Syed Ali
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Kaisar, Nahid
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Wu, Sheng Hui
;
Chen, Hsin-An
Despite issues related to dendrite formation, research on Li metal anodes has resurged because of their high energy density. In this study, graphene oxide (GO) layers are decorated onto Li metal anodes through a simple process of drop-casting and spray-coating. The self-assembly of GO is exploited to synthesize coatings having compact, mesoporous, and macroporous morphologies. The abilities of the GO coatings to suppress dendrite formation are compared through Li vertical bar Li symmetrical cell charging at a current density of 5 mA cm(-2) for 2000 cycles-a particularly abusive test. The macroporous structure possesses the lowest impedance, whereas the compact structure excels in terms of stability. Moreover, GO exhibits a low nucleation overpotential and is transformed into reduced GO with enhanced conductivity during the operation of the cells; both factors synergistically mitigate the issue of dendrite formation. Li-S batteries incorporating the GO-decorated Li anodes exhibit an initial capacity of 850 mA h g(-1) and maintain their stability for 800 cycles at a C-rate of 1 C (1675 mA h g(-1)), suggesting the applicability of GO in future rechargeable batteries.
The effect of solvent induced crystallinity of polymer layer on poly(3-hexylthiophene)/C-70 bilayer solar cells
(2011-02-01)
Kekuda, Dhananjaya
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Lin, Hao-Shing
;
Wu, Meng Chyi
;
Huang, Jen-Shein
;
Ho, Kuo-Chuan
A bilayer polymer solar cell is demonstrated with the device configuration ITO/PEDOT:PSS/poly(3-hexylthiophene)/C-70/Al. In this article, we highlight the importance of polymer surface morphology, its crystallinity and mobility on device output parameters. The solvent used for polymer processing plays a major role in deciding these parameters and it was observed that high boiling point solvents are desirable for achieving large surface roughness of the polymer layer, which in turn provide more interface area in the bilayer device structure. Due to the increased interface area for exciton dissociation, these bilayer devices resulted in a maximum power conversion efficiency of 3.65% under one sun radiation. (C) 2010 Elsevier B.V. All rights reserved.

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