Browsing by Author "Yang, Chang-Chung"

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Applications of novel dithienothiophene- and 2,7-carbazole-based conjugated polymers with surface-modified ZnO nanoparticles for organic photovoltaic cells
(2011-05-31)
Fang, Hsiao-Ping
;
Chiang, I-Hung
;
Chu, Chih-Wei
;
Yang, Chang-Chung
;
Lin, Hong-Cheu
Two kinds of novel conjugated polymers containing 2,7-carbazole, thiophene, and fused-dithienothiophene rings as backbones bearing acid-protected and benzoic acid pendants (PC1 and PC2, respectively) were utilized for organic solar cell applications. The absorption spectra of these polymers (in both solutions and solid films) showed an absorption range at 300-580 nm. Furthermore, ZnO nanoparticles were synthesized and surface-modified with pyridyl surfactants (ZnOpy) to be ca. 3-4 nm. The pyridyl surfactants of ZnOpy nanoparticles (as electron acceptors to partially replace expensive electron acceptor PCBM) not only induce supramolecular interactions with benzoic acid pendants of polymer PC2 via H-bonds, but also enhance the homogeneous dispersions of ZnOpy nanoparticles in polymer PC2. Thus, the ternary systems of PC1-N2/ZnOpy/PCBM in weight ratios of 1:0.05:1 and 1:0.1:1 were investigated in bulk heterojunction polymer solar cells (PSCs). Under the standard illumination of AM 1.5, 100 mW/cm(2), the best power conversion efficiency (PCE) of the PSC cell containing a polymer blend of PC2/ZnOpy/PCBM = 1:0.05:1 reached PCE = 0.55%, with J(sc) = 2.11 mA/cm(2), V(oc) = 0.88 V, and FF = 29.4%. (C) 2011 Elsevier B.V. All rights reserved.
Novel narrow-band-gap conjugated copolymers containing phenothiazine-arylcyanovinyl units for organic photovoltaic cell applications
(2008-07-01)
Li, Kuang-Chieh
;
Hsu, Ying-Chan
;
Lin, Jiann-T'Suen
;
Yang, Chang-Chung
;
Wei, Kung-Hwa
A series of novel narrow-band-gap copolymers (P1-P12) composed of alkyl-substituted fluorene (FO) units and six analogous mono- and bis(2-aryl-2-cyano-vinyl)- 10-hexylphenothiazine monomers (M1-M6) were synthesized by a palladium-catalyzed Suzuki coupling reaction with two different feed in ratios of FO to M1-M6 (molar ratio = 3:1 and 1:1). The absorption spectra of polymers P1-P12 exhibited broad peaks located in the UV and visible regions from 400 to 800 nm with optical band gaps at 1.55-2.10 eV, which fit near the wavelength of the maximum solar photon reflux. Electrochemical experiments displayed that the reversible p- and n-doping processes of copolymers were partially reversible, and the proper HOMO/LUMO levels enabled a high photovoltaic open-circuit voltage. As blended with [6,6]-phenyl C-61 butyric acid methyl ester (PCBM) as an electron acceptor in bulk heterojunction photovoltaic devices, narrow-band-gap polymers P1-P12 as electron donors showed significant photovoltaic performance which varied with the intramolecular donor-acceptor interaction and their mixing ratios to PCBM. Under 100 mW/cm(2) of AM 1.5 white-light illumination, the device of copolymer P12 produced the highest preliminary result having an open-circuit voltage of 0.64 V, a short-circuit current of 2.70 mA/cm(2), a fill factor of 0.29, and an energy conversion efficiency of 0.51%. (c) 2008 Wiley Periodicals, Inc.
Soluble Narrow-Band-Gap Copolymers Containing Novel Cyclopentadithiophene Units for Organic Photovoltaic Cell Applications
(2009-04-15)
Li, Kuang-Chieh
;
Hsu, Ying-Chan
;
Lin, Jiann-T'suen
;
Yang, Chang-Chung
;
Wei, Kung-Hwa
Five novel conjugated copolymers (P1-P5) containing coplanar cyclopentadithiophene (CPDT) units (incorporated with arylcyanovinyl and keto groups in different molar ratios) were synthesized and developed for the applications of polymer solar cells (PSCs). Polymers P1-P5 covered broad absorption ranges from U-V to near infrared (400-900 nm) with narrow optical band gaps of 1.38-1.70 eV, which are compatible with the maximum solar photon reflux. Partially reversible p- and n-doping processes of P1-P5 in electrochemical experiments were observed, and the proper molecular design for highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels of P1-P5 induced the highest photovoltaic open-circuit voltage in the PSC devices, compared with those previously reported CPDT-based narrow-band-gap polymers. Powder X-ray diffraction (XRD) analyses suggested that these copolymers formed self-assembled pi-pi stacking and pseudobilayered structures. Under 100 mW/cm(2) of AM 1.5 white-light illumination, bulk hetero-junction PSC devices containing an active layer of electron donor polymers P1-P5 mixed with electron acceptor [6,6]-phenyl C(61) butyric acid methyl ester (PCBM) in the weight ratio of 1:4 were investigated. The PSC device containing P1 gave the best preliminary result with an open-circuit voltage of 0.84 V, a short-circuit current of 2.36 mA/cm(2), and a fill factor of 0.38, offering an overall power conversion efficiency (PCE) of 0.77% as well as a maximal quantum efficiency of 23% from the external quantum efficiency (EQE) measurements. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2073-2092, 2009