Browsing by Author "He, Yuehui"

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A High-Mobility Low-Bandgap Copolymer for Efficient Solar Cells
(2010-12-15)
Ding, Ping
;
Chu, Cheng-Che
;
Liu, Bo
;
Peng, Bo
;
Zou, Yingping
A new high-mobility low-bandgap polymer, PBDT-DODTBT, based on benzodithiophene and 5,6-bis(octyloxy)-4,7-di(thiophen-2-yl) benzothiadiazole has been synthesized through a standard Stille coupling reaction. The polymer is soluble in common organic solvents, such as chloroform, tetrahydrofuran, and chlorobenzene and has excellent film forming properties. Preliminary studies of the copolymer showed the charge mobility as high as 7.15 x 10(-3) cm(2).V(-1). s(-1) from SCLC measurement. Initial photovoltaic cells based on the composite structure of ITO/PEDOT: PSS/PBDT-DODTBT: (alpha)PC(71)BM (1:2)/Ca/Al showed an open-circuit voltage of 0.76 V, a power conversion efficiency of 4.02%, and a short-circuit current of 8.96mA.cm(-2).
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).