School of Chemistry - Research Publications
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ItemThiazolyl substituted benzodithiophene copolymers: synthesis, properties and photovoltaic applications(Royal Society of Chemistry, 2014)Three new conjugated polymers based on 5-decylthiazol-2-yl substituted benzodithiophene have been synthesized by Stille cross-coupling polymerization. 1,3-Dibromo-5-octylthieno[3,4-c]pyrrole-4,6-dione (M1), 2,5-diethylhexyl-3,6-bis(5-bromothiophen-2-yl)pyrrolo[3,4-c]-pyrrole-1,4-dione (M2) and 4,6-dibromo-thieno[3,4-b]thiophene-2-dodecyl carboxylate (M3) were used as acceptor building blocks for the synthesis of conjugated donor-acceptor polymers. The thermal, optical, electrochemical, and photovoltaic properties of the synthesized polymers were studied.
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ItemMorphology Change and Improved Efficiency in Organic Photovoltaics via Hexa-peri-hexabenzocoronene Templates(AMER CHEMICAL SOC, 2014-06-11)The morphology of the active layer in organic photovoltaics (OPVs) is of crucial importance as it greatly influences charge generation and transport. A templating interlayer between the electrode and the active layer can change active layer morphology and influence the domain orientation. A series of amphiphilic interface modifiers (IMs) combining a hydrophilic polyethylene-glycol (PEG) oligomer and a hydrophobic hexabenzocoronene (HBC) were designed to be soluble in PEDOT:PSS solutions, and surface accumulate on drying. These IMs are able to self-assemble in solution. When IMs are deposited on top of a poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) film, they induce a morphology change of the active layer consisting of discotic fluorenyl-substituted HBC (FHBC) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM). However, when only small amounts (0.2 wt %) of IMs are blended into PEDOT:PSS, a profound change of the active layer morphology is also observed. Morphology changes were monitored by grazing incidence wide-angle X-ray scattering (GIWAXS), transmission electron microscopy (TEM), TEM tomography, and low-energy high-angle angular dark-field scanning transmission electron microscopy (HAADF STEM). The interface modification resulted in a 20% enhancement of power conversion efficiency.
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ItemNo Preview AvailableThe role of solvent vapor annealing in highly efficient air-processed small molecule solar cells(ROYAL SOC CHEMISTRY, 2014)
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ItemA molecular nematic liquid crystalline material for high-performance organic photovoltaics(NATURE PUBLISHING GROUP, 2015-01)Solution-processed organic photovoltaic cells (OPVs) hold great promise to enable roll-to-roll printing of environmentally friendly, mechanically flexible and cost-effective photovoltaic devices. Nevertheless, many high-performing systems show best power conversion efficiencies (PCEs) with a thin active layer (thickness is ~100 nm) that is difficult to translate to roll-to-roll processing with high reproducibility. Here we report a new molecular donor, benzodithiophene terthiophene rhodanine (BTR), which exhibits good processability, nematic liquid crystalline behaviour and excellent optoelectronic properties. A maximum PCE of 9.3% is achieved under AM 1.5G solar irradiation, with fill factor reaching 77%, rarely achieved in solution-processed OPVs. Particularly promising is the fact that BTR-based devices with active layer thicknesses up to 400 nm can still afford high fill factor of ~70% and high PCE of ~8%. Together, the results suggest, with better device architectures for longer device lifetime, BTR is an ideal candidate for mass production of OPVs.
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ItemEffect of molecular weight on the properties and organic solar cell device performance of a donor-acceptor conjugated polymer(ROYAL SOC CHEMISTRY, 2015)
The effect of molecular weight of a conjugated polymer on its photophysical properties and solar cell device performance was investigated.
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ItemSynthesis and photovoltaic properties of thieno[3,2-b]thiophenyl substituted benzo[1,2-b:4,5-b ']dithiophene copolymers(ROYAL SOC CHEMISTRY, 2014)A new benzo[1,2-b:4,5-b']dithiophene (BDT) building block with 4,8-disubstitution using 2-(2-ethylhexyl)-3-hexylthieno[3,2-b]thiophene as the substituent has been designed and synthesized. The new building block has been copolymerized with benzothiadiazole (BT) and 5,6-difluorobenzothiadiazole (fBT) by Suzuki and Stille coupling polymerization to synthesize donor-acceptor conjugated polymers. The optical and electrochemical properties of the synthesized copolymers were studied. Bulk heterojunction solar cells were fabricated using the donor-acceptor copolymers in conjunction with PC71BM and exhibited up to 4.20% power conversion efficiency.