Browsing by Author "Yuan, Mao-Chuan"

Now showing 1 - 9 of 9

A crystalline low-bandgap polymer comprising dithienosilole and thieno[3,4-c] pyrrole-4,6-dione units for bulk heterojunction solar cells
(2011-06-08)
Yuan, Mao-Chuan
;
Chou, Yi-Jen
;
Chen, Chia-Min
;
Hsu, Chang-Lung
;
Wei, Kung-Hwa
We have used Stille coupling polymerization to synthesize a new low-bandgap conjugated polymer, PDTSTPD, that consists of an electron-rich dithieno[3,2-b:2',3'-d]-silole (DTS) unit and an electron-deficient thieno[3,4-c]pyrrole-4,6-dione (TPD) moiety. The polymer exhibited an excellent thermal stability, crystalline characteristics, a broad spectral absorption, and a deep highest occupied molecular orbital (HOMO) energy level, resulting from combination of the rigid TPD and the coplanar DTS units in the polymer backbone. Moreover, the presence of the silicon atoms along the polymer chain ensured PDTSTPD having strong interchain stacking and good hole mobility. An optimal device incorporating the PDTSTPD:PC(71)BM blend at a weight ratio of 1:1 provided a power conversion efficiency of 3.42%. (c) 2011 Elsevier Ltd. All rights reserved.
A Thieno[3,4-c]pyrrole-4,6-dione-Based Donor-Acceptor Polymer Exhibiting High Crystallinity for Photovoltaic Applications
(2010-09-14)
Yuan, Mao-Chuan
;
Chiu, Mao-Yuan
;
Liu, Shih-Pin
;
Chen, Chia-Min
;
Wei, Kung-Hwa
Crystalline donor-acceptor conjugated polymers for bulk heterojunction photovoltaics
(2013)
Jiang, Jian-Ming
;
Yuan, Mao-Chuan
;
Dinakaran, K.
;
Hariharan, A.
;
Wei, Kung-Hwa
Molecular engineering of conjugated polymers for tuning their energy bands is an important process in the quest for highly efficient bulk heterojunction (BHJ) polymer photovoltaic devices. One effective approach is to construct a conjugated polymer by conjugating two chemical units possessing different electron donating (donor) and accepting (acceptor) capabilities. Conjugated copolymers featuring donor-acceptor (D/A) subunits are promising materials for solar cell applications because of their tunable energy bands and solubility that can be tailored to the performances of the photovoltaic devices. Under proper processing conditions, the conjugated polymers with rigid and planar D/A segments can undergo self-assembly to form crystalline structures that improve charge carrier mobility and provide better resistance to the permeation of water and oxygen compared to amorphous polymers. Conjugated polymers with D/A structure have been investigated thoroughly over the last few years. In this highlight, we present an overview of recent developments in BHJ organic photovoltaics employing D/A crystalline copolymers as active layer materials for photon-to-electron conversion, with particular emphasis on crystalline D/A polymers featuring newly developed acceptor structures, including thieno [3,4-c]pyrrole-4,6-dione, diketo-pyrrole-pyrrole, bithiazole, thiazolothiazole and thieno[3,2-b]thiophene moieties, and conclude with future perspectives.
Improving Device Efficiency of Polymer/Fullerene Bulk Heterojunction Solar Cells Through Enhanced Crystallinity and Reduced Grain Boundaries Induced by Solvent Additives
(2011-08-02)
Su, Ming-Shin
;
Kuo, Chih-Yin
;
Yuan, Mao-Chuan
;
Jeng, U-Ser
;
Su, Chun-Jen
The power conversion efficiency of a device incorporating a crystalline polymer/fullerene thin film improves from 5% to 7.3% - a relative increase of 45% - when an additive, diiodohexane (DIH), is present during processing. The DIH-processed active layer exhibits substantially enhanced polymer crystallinity and smaller fractal-like fullerene clusters.
Novel carbazole/fluorene hybrids: Host materials for blue phosphorescent OLEDs
(2006-06-22)
Shih, Ping-I
;
Chiang, Chih-Long
;
Dixit, Ajay Kumar
;
Chen, Ching-Kun
;
Yuan, Mao-Chuan
A series of carbazole/fluorene (CBZm-Fn) hybrids were effectively synthesized through Friedel-Crafts-type substitution of the carbazole rings. These compounds were thermally and morphologically stable host materials for OLED applications. Efficient blue phosphorescent OLEDs were obtained when employing CBZ1-F2 as the host and Firpic as the guest.
Polymers derived from 3,6-fluorene and tetraphenylsilane derivatives: Solution-processable host materials for green phosphorescent OLEDs
(2008-06-10)
Yeh, Huan-Chi
;
Chien, Chen-Han
;
Shih, Ping-I
;
Yuan, Mao-Chuan
;
Shu, Ching-Fong
We have synthesized two fluorene-based polymeric host materials, P1 and P2, through palladium-catalyzed Suzuki couplings of monomers containing tetraphenylsilane and 3,6-disubstituted fluorene frameworks, respectively. The resultant copolymers exhibited high glass transition temperatures (T-g >= 215 degrees C) and excellent thermal stability. The conjugation lengths of polymers P1 and P2 were effectively confined through the presence of the 3,6-linkages and silane units in the polymer skeleton. The structural features endowed these copolymers with UV-violet emissions in the solid state, together with high triplet energies (E-T = 2.60 eV), which were sufficiently high for PI and P2 to serve as appropriate hosts for green-emitting phosphors. In the case of polymer P2, the incorporation of pendent carbazole groups increased the HOMO level markedly and balanced the rates of charge injection and transportation. Employing P2 doped with green-emitting fac-tris(2-phenylpyridine)iridium as the emissive layer, we fabricated highly efficient polymer light-emitting diodes (32 cd/A, 9.2%) that exhibited significantly enhanced EL performance relative to that of the system employing P1 (14.5 cd/A, 4.2%).
Synthesis and characterization of a polyfluorene containing carbazole and oxadiazole dipolar pendent groups and its application to electroluminescent devices
(2007-07-15)
Yuan, Mao-Chuan
;
Shih, Ping-I
;
Chien, Chen-Han
;
Shu, Ching-Fong
;
應用化學系
We have synthesized a blue-light-emitting polyfluorene (PF) derivative (PF-CBZ-OXD) that presents bulky bole-transporting carbazole and electron-transporting oxadiazole pendent groups functionalized. at the C-9 positions of alternating fluorene units. The results from photoluminescence and electrochemical measurements indicate that both the side chains and the PF main chain retain their own electronic characteristics in the copolymer. An electroluminescent device incorporating this polymer as the emitting layer was turned on at 4.5 V; it exhibited a stable blue emission with a maximum external quantum efficiency of 1.1%. Moreover, we doped PF-CBZ-OXD and its analogue PF-TPA-OXD with a red-light-emitting iridium phosphor for use as components of phosphorescent red-light emitters to investigate the effect of the host's HOMO energy level on the degree of charge trapping and on the electrophosphorescent efficiency. We found that spectral overlap and individual energy level matching between the host and guest were both crucial features affecting the performance of the electroluminescence devices. Atomic force microscopy measurements indicated that the dipolar nature of PF-CBZ-OXD, in contrast to the general nonpolarity of polydialkylfluorenes, provided a stabilizing environment that allowed homogeneous dispersion of the polar iridium triplet dopant. (c) 2007 Wiley Periodicals, Inc.
Synthesis and Characterization of Donor-Bridge-Acceptor Alternating Copolymers Containing Perylene Diimide Units and Their Application to Photovoltaic Cells
(2010-03-15)
Yuan, Mao-Chuan
;
Su, Ming-Hsin
;
Chiu, Mao-Yuan
;
Wei, Kung-Hwa
;
材料科學與工程學系
We have used Suzuki coupling to prepare a series of alternating copolymers featuring coplanar cyclopentadithiophene and hole-transporting carbazole units. We observed quenching in the photoluminescence spectra of our polymers after incorporating pendent electron-deficient perylene diimide (PDI) moieties on the side chains, indicating more efficient photoinduced electron transfer. Electrochemical measurements revealed that the PDI-containing copolymers displayed reasonable and sufficient offsets of the energy levels of their lowest unoccupied molecular orbitals for efficient charge dissociation. The performance of bulk heterojunction photovoltaic cells incorporating the copolymer/[6,6]-phenyl-C(61)-butyric acid methyl ester blends (1:4, w/w) was optimized when the active layer had a thickness of 70 nm. The photocurrents of the devices were enhanced as a result of the presence of the PDI moieties, thereby leading to improved power conversion efficiencies. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1298-1309, 2010
Synthesis and Characterization of Pyrido[3,4-b]pyrazine-Based Low-Bandgap Copolymers for Bulk Heterojunction Solar Cells
(2010-08-10)
Yuan, Mao-Chuan
;
Chiu, Mao-Yuan
;
Chiang, Chien-Ming
;
Wei, Kung-Hwa
;
材料科學與工程學系
We have used Stille polycondensation to prepare a series of low-bandgap copolymers, P1-P4, by conjugating the electron-accepting pyrido[3,4-b]pyrazine (PP) moieties with the electron-rich benzo[1,2-b:3,4-b']dithiophene (BDT) or cyclopentadithiophene (CPDT) units. P1 and P3 are based on PP and BDT units while P2 and P4 are based on PP and CPDT units. All of these polymers exhibited excellent thermal stability and sufficient energy offsets for efficient charge transfer and dissociation, as determined through thermogravimetric analyses and cyclic voltammetry, respectively. The bandgaps of the polymers could be tuned in the range 1.46-1.60 eV by using the two different donors, which have different electron-donating abilities. The three-component copolymers, P3 and P4, incorporating the thiophene and bithiophene segments, respectively, absorbed broadly, covering the solar spectrum from 350 to 800 nm. The morphologies of the blends of P3 and P4 with [6,6]-phenyl-C(70)-butyric acid methyl ester (PC(70)BM) were more homogeneous than those of P1 and P2; in addition, devices incorporating the P3 and P4 blends exhibited superior performance. The best device performance resulted from an active layer containing the P4:PC(70)BM blend; the short-circuit current was 10.85 mA cm(-2) and the power conversion efficiency was 3.15%.