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Your search keyword '"Chang, Jui-Fen"' showing total 44 results
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44 results on '"Chang, Jui-Fen"'

3. Determining exciton bandwidth and film microstructure in polythiophene films using linear absorption spectroscopy

Author

Clark, Jenny, Chang, Jui-Fen, Spano, Frank C., Friend, Richard H., and Silva, Carlos

Subjects
Condensed Matter - Materials Science
Abstract

We analyze the linear absorption spectrum of regioregular poly(3-hexylthiophene) films spun from a variety of solvents to probe directly the film microstructure and how it depends on processing conditions. We estimate the exciton bandwidth and the percentage of the film composed of aggregates quantitatively using a weakly interacting H-aggregate model. This provides a description of the degree and quality of crystallites within the film and is in turn correlated with thin-film field-effect transistor characteristics., Comment: Applied Physics Letters (in press); 9 pages, three figures

Published
2009
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5. Charge transport mechanisms of microcrystalline conjugated polymer thin film transistors

Author

Chang, Jui-Fen

Subjects
621.3
Abstract

This thesis is concerned with a prototype microcrystalline semiconducting polymer, poly(3-hexylthiophene) (P3HT), incorporated into a thin-film transistor structure in a bottom gate configuration with n-doped silicon as gate contacts and SiO2 as gate dielectric. The mechanisms to influence the charge transport in P3HT thin films are investigated in detail from experiments and theoretical analyses. Crystallisation of P3HT polymer during the spin-coating process is limited by the drying time of solvent. Compared with the most commonly used solvent, chloroform, it is demonstrated that choosing appropriate solvents with good solubility and higher boiling point for sufficiently high molecular weight (MW) P3HT could help improve its crystallinity and in-plane orientation of π-π stacking, leading to an enhanced field-effect mobility. In high crystalline P3HT films the microcrystals in nanoribbon shape are also observed. More comprehensively, the field-effect mobility of P3HT related to the macroscopic morphology and microstructures is studied as a function of MW of polymers and thin film processing conditions. From comparative studies of transistor characteristics, film morphology, and spectroscopic properties, it is shown that the crystalline quality of P3HT nanoribbons which depends on the chain folding kinetics and polymer chain lengths plays a decisive role to determine the MW dependence of mobility. The highest mobilities above 0.1 cm2/Vs can be achieved in highly-crystalline, sufficiently high-MW polymers. However, the mobility is found to saturate at high-MW regime due to the residual conformational disorder in polymer microcrystals probably arising from the intrinsic properties or crystallization kinetics of long chains, which need to be addressed to improve mobility further.

Published
2007

16. General observation of n-type field-effect behaviour in organic semiconductors

Author

Chua, Lay-Lay, Zaumseil, Jana, Chang, Jui-Fen, Ou, Eric C.-W., Ho, Peter K.-H., Sirringhaus, Henning, and Friend, Richard H.

Subjects
Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Author(s): Lay-Lay Chua [1, 2]; Jana Zaumseil [1]; Jui-Fen Chang [1]; Eric C.-W. Ou [3]; Peter K.-H. Ho (corresponding author) [1, 2]; Henning Sirringhaus [1]; Richard H. Friend (corresponding author) [...]

Published
2005
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18. Electroluminescence and photoluminescence studies on carrier radiative and nonradiative recombinations in metal-oxide-silicon tunneling diodes.

Author

Chen, Miin-Jang, Chang, Jui-Fen, Yen, Jia-Liang, Tsai, Chen S., Liang, Eih-Zhe, Lin, Ching-Fuh, and Liu, C. W.

Subjects
*ELECTROLUMINESCENCE, *PHOTOLUMINESCENCE, *DIODES, *METAL oxide semiconductors
Abstract

Electroluminescence (EL) and photoluminescence (PL) measurements at silicon band gap energy from metal-oxide-semiconductor tunneling diodes on silicon have been carried out to study the carrier radiative recombination and nonradiative recombination near the silicon/silicon dioxide (Si/SiO[sub 2]) interface. The temporal EL response indicates that the radiative recombination coefficient involved is as much as ten times greater than that of the bulk silicon. However, the nonradiative recombination is still the dominant carrier recombination process. Voltage-dependent PL shows that PL intensity increases with the bias voltage. This voltage dependence is attributed to the variations of nonradiative recombination rates due to the change of Fermi level with the bias voltage. The intensity of EL is found to be less temperature dependent than that of PL. The near-band-edge Fermi level for EL leads to the reduced and less thermal-active nonradiative recombination as compared to PL. This study shows that Fermi level near the Si/SiO[sub 2] interface strongly influences the nonradiative recombination rates and the resulting EL and PL intensities. [ABSTRACT FROM AUTHOR]

Published
2003
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20. Low Thresholds for a Nonconventional Polymer Blend-Amplified Spontaneous Emission and Lasing in F8(1-x):SYx System

Author

Umair Hassan, Muhammad, Liu, Yee-Chen, Butt, Haider, Hasan, Kamran, Chang, Jui-Fen, Abigael Olawoyin, Ayooye, Henry Friend, Richard, Umair Hassan, Muhammad, Liu, Yee-Chen, Butt, Haider, Hasan, Kamran, Chang, Jui-Fen, Abigael Olawoyin, Ayooye, and Henry Friend, Richard

Abstract

A mixture of two polymer materials, poly (9,9-dioctylfluorene) (F8), and one of the poly(para-phenylenevinylene) derivatives, superyellow (SY) have been used to make F8(1-x):SYx polymer blend system. Under a 3-5 ns pulsed-laser excitation, this system showed excellent optical properties with low threshold values of approximate to 14 mJ/cm(2) and approximate to 8 mJ/cm(2) for amplified spontaneous emission and optically pumped lasing, respectively. The proposed system was also electroluminescent and an interesting candidate for future research on polymer injection lasers. (C) 2015 Wiley Periodicals, Inc.

Published
2016
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26. All-polymer field-effect transistors using a brush gate dielectric

Author

Rodríguez, Ana B., primary, Tomlinson, Michael R., additional, Khodabakhsh, Saghar, additional, Chang, Jui-Fen, additional, Cousin, Fabrice, additional, Lott, Dieter, additional, Sirringhaus, Henning, additional, Huck, Wilhelm T. S., additional, Higgins, Anthony M., additional, and Geoghegan, Mark, additional

Published
2013
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27. Low thresholds for a nonconventional polymer blend-Amplified spontaneous emission and lasing in F81− x: SY x system.

Author

Hassan, Muhammad Umair, Liu, Yee‐Chen, Butt, Haider, Hasan, Kamran ul, Chang, Jui‐Fen, Olawoyin, Ayooye Abigael, and Friend, Richard Henry

Subjects
PHOTON emission, OPTICAL pumping, POLYMER blends, ACTIVE medium, FLUORESCENCE resonance energy transfer
Abstract

ABSTRACT A mixture of two polymer materials, poly (9,9-dioctylfluorene) (F8), and one of the poly( para-phenylenevinylene) derivatives, superyellow (SY) have been used to make F81− x:SY x polymer blend system. Under a 3-5 ns pulsed-laser excitation, this system showed excellent optical properties with low threshold values of ≈14 µJ/cm2 and ≈8 µJ/cm2 for amplified spontaneous emission and optically pumped lasing, respectively. The proposed system was also electroluminescent and an interesting candidate for future research on polymer injection lasers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 15-21 [ABSTRACT FROM AUTHOR]

Published
2016
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31. Hall-Effect Measurements Probing the Degree of Charge-Carrier Delocalization in Solution-Processed Crystalline Molecular Semiconductors

Author

Chang, Jui-Fen, primary, Sakanoue, Tomo, additional, Olivier, Yoann, additional, Uemura, Takafumi, additional, Dufourg-Madec, Marie-Beatrice, additional, Yeates, Stephen G., additional, Cornil, Jérôme, additional, Takeya, Jun, additional, Troisi, Alessandro, additional, and Sirringhaus, Henning, additional

Published
2011
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44. Ultrastrong coupling in Super Yellow polymer microcavities and development of highly efficient polariton light-emitting diodes and light-emitting transistors.

Author

Chang JF, Zheng YC, Chiang CY, Huang CK, and Jaing CC

Abstract

We present detailed studies on exciton-photon coupling and polariton emission based on a poly(1,4-phenylenevinylene) copolymer, Super Yellow (SY), in a series of optical microcavities and optoelectronic devices, including light-emitting diode (LED) and light-emitting transistor (LET). We show that sufficiently thick SY microcavities can generate ultrastrong coupling with Rabi splitting energies exceeding 1 eV and exhibit spectrally narrow, nearly angle-independent photoluminescence following lower polariton (LP) mode dispersion. When the microcavity is designed with matched LP low-energy state and exciton emission peak for radiative pumping, the conversion efficiency from exciton to polariton emission can reach up to 80%. By introducing appropriate injection layers in a SY microcavity and optimizing the cavity design, we further demonstrate a high-performance ultrastrongly coupled SY LED with weakly dispersive electroluminescence along LP mode and a maximum external quantum efficiency (EQE) of 2.8%. Finally, we realize an ultrastrongly coupled LET based on vertical integration of a high-mobility ZnO transistor and a SY LED in a microcavity, which enables a large switching ratio, uniform emission in the ZnO pattern, and LP mode emission with a maximum EQE of 2.4%. This vertical LET addresses the difficulties of achieving high emission performance and precisely defining the emission area in typical planar LETs, and opens up the possibility of applying various strongly coupled emitters for advanced polariton devices and high-resolution applications.

Published
2023
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