Browsing by Author "Xiao, Dequan"

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Effects of thiophene units on substituted benzothiadiazole and benzodithiophene copolymers for photovoltaic applications
(2012-09-05)
Ding, Ping
;
Zou, Yingping
;
Chu, Cheng-Che
;
Xiao, Dequan
;
Hsu, Chain-Shu
Two conjugated copolymers, poly{4,7-[5,6-bis(octyloxy)]benzo(c)(1,2,5)thiadiazole-alt-4,8-di(2-ethylhexyloxyl)benzo[1,2-b:3,4-b]dithiophene} (P1) and poly(2-{5-[5,6-bis(octyloxy)-4-(thiophen-2-yl)benzo(c)(1,2,5)thiadiazol-7-yl] thiophen-2-yl}-4,8-di(2-ethylhexyloxyl)benzo(1,2-b:3,4-b)dithiophene) (P2), composed of benzodithiophene and 5,6-dioctyloxybenzothiadiazole derivatives with or without thiophene units were synthesized via a Stille cross-coupling polymerization reaction. These copolymers are promising for applications in bulk heterojunction solar cells because of their good solubility, proper thermal stability, moderate hole mobility, and low band gap. The photovoltaic properties of these copolymers were investigated on the basis of blends of the different polymer/(6,6)-phenyl-C71-butyric acid methyl ester (PC71BM) weight ratios under AM1.5G illumination at 100 mW/cm2. The device with indium tin oxide/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)/P2:PC71BM (1 : 2 w/w)/Ca/Al gave a relatively better photovoltaic performance with a power conversion efficiency of 1.55%. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Incorporation of Fluorine onto Different Positions of Phenyl Substituted Benzo[1,2-b:4,5-b ']dithiophene Unit: Influence on Photovoltaic Properties
(2015-07-14)
Yuan, Jun
;
Zou, Yingping
;
Cui, Ruth
;
Chao, Yi-Hsiang
;
Wang, Zaiyu
We have designed and synthesized two low bandgap conjugated copolymers containing alternating meta-fluoro-p-alkoxyphenyl- (m-FPO-) or p-fluoro-m-alkoxyphenyl- (p-FPO-) substituted benzodithiophenes-co-benzooxadiazole (BO), named PBO-m-FPO and PBO-p-FPO. The properties, including UV-vis absorption, charge mobility and photovoltaic performance of the two polymers have been intensively investigated. The results indicated that the introduction of fluorine atom at m, p positions of phenyl substituted benzodithiophene unit hardly affected their absorption spectra and highest occupied molecular orbital (HOMO) level. However, the two polymers showed different photovoltaic properties. Power conversion efficiencies (PCEs) based on the device structure of ITO/PEDOT:PSS/polymer:PC71BM/Ca/Al demonstrated a large distinction (5.9% for PBO-m-FPO vs 2.8% for PBO-p-FPO) at optimal weight ratio. When replacing the Ca layer with zirconium acetylacetonate (ZrAcac), using 3% 1,8-diiodooctane (DIO) as the active layer additive, the PCEs of PBO-m-FPO and PBO-p-FPO increased by 36% (8.0% vs 5.9%) and 85% (5.1% vs 2.8%), respectively. The active layer\'s mobilities, morphology and molecular packing resulted in a significant difference in short-circuit current density (J(sc)) and fill factor (FF).
New Low Bandgap Conjugated Polymer Derived from 2, 7-Carbazole and 5, 6-Bis(octyloxy)-4, 7-di(thiophen-2-yl) Benzothiadiazole: Synthesis and Photovoltaic Properties
(2012-01-05)
Ding, Ping
;
Chu, Cheng-Che
;
Zou, Yingping
;
Xiao, Dequan
;
Pan, Chunyue
To develop conjugated polymers with low bandgap, deep HOMO level, and good solubility, a new conjugated alternating copolymer PC-DODTBT based on N-9'-heptadecanyl-2,7-carbazole and 5, 6-bis(octyloxy)-4,7di(thiophen-2-yl) benzothiadiazole was synthesized by Suzuki cross-coupling polymerization reaction. The polymer reveals excellent solubility and thermal stability with the decomposition temperature (5% weight loss) of 327 degrees C. The HOMO level of PC-DODTBT is -5.11 eV, indicating that the polymer has relatively deep HOMO level. The hole mobility of PC-DODTBT as deduced from SCLC method was found to be 2.03 x 10(-4) cm(2)/Versus Polymer solar cells (PSCs) based on the blends of PC-DODTBT and [6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71)BM) with a weight ratio of 1:2.5 were fabricated. Under AM 1.5 (AM, air mass), 100 mW/cm(-2) illumination, the devices were found to exhibit an open-circuit voltage (V(oc)) of 0.73 V, short-circuit current density (J(sc)) of 5.63 mA/cm(-2), and a power conversion efficiency (PCE) of 1.44%. This photovoltaic performance indicates that the copolymer is promising for polymer solar cells applications. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 99-107, 2012