Thiazolyl substituted benzodithiophene copolymers: synthesis, properties and photovoltaic applications (original) (raw)
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Journal of Applied Polymer Science, 2012
Two conjugated copolymers, poly{4,7-[5,6bis(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-[5,6bis(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 proper-ties of these copolymers were investigated on the basis of blends of the different polymer/(6,6)-phenyl-C 71 -butyric acid methyl ester (PC 71 BM) weight ratios under AM1.5G illumination at 100 mW/cm 2 . The device with indium tin oxide/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)/P2:PC 71 BM (1 : 2 w/w)/Ca/Al gave a relatively better photovoltaic performance with a power conversion efficiency of 1.55%. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125: 3936-3945, 2012
Organic Electronics, 2013
A series of polymers, poly{5,6-bis(decyloxy)-4-(thiophen-2-yl)benzo[c][1,2,5]oxadiazole} (1T-BO20), poly{4-(2,2 0-bithiophen-5-yl)-5,6-bis(decyloxy)benzo[c][1,2,5]oxadiazole} (2T-BO20), poly{4-(2,2 0-bithiophen-5-yl)-5,6-bis(decyloxy)-7-(thiophen-2-yl)benzo[c][1,2,5] oxadiazole} (3T-BO20) containing 2,1,3-benzooxadiazole derivative and different thiophene rings are synthesized. Effect of the number of thiophene rings on the optical, electrochemical and photovoltaic properties of the polymers is investigated. The maximum absorption wavelength and the optical band gap of the polymers are almost the same, indicating the polymers exhibit similar intramolecular charge transfer effect. The HOMO levels are in the order of 1T-BO20 (À5.60 eV) < 2T-BO20 (À5.45 eV) < 3T-BO20 (À5.36 eV), revealing that the HOMO level of the polymers are dependent of number of thiophene ring in the back bone. Under the illumination of AM 1.5G, 100 mW/cm 2 , the power conversion efficiency (PCE) of PSCs based on these polymers increases in the order of 1T-BO20 (1.66%), 2T-BO20 (1.71%) and 3T-BO20 (1.92%). Besides, we find that the efficiency of PSCs showed very different responses by the addition of DIO as a processing additive. The devices based on 1T-BO20 and 2T-BO20 with DIO exhibit an enhancement of PCE from 1.66% to 3.65% and from 1.71% to 2.40%, respectively, whereas PCE of the device based on 3T-BO20 with DIO decreased from 1.92% to 1.76%.
Journal of Polymer Science Part A: Polymer Chemistry, 2010
Two conjugated main-chain polymers consisting of heteroarene-fused p-conjuagted donor moiety alternating with 4,7-bis(5-bromo-4-octylthiophen-2-yl)benzo[c][1,2,5]thiadiazole (P1) or 2,5-bis(5-bromo-4-octylthiophen-2-yl) thiazolo[5,4-d]thiazole (P2) units have been synthesized. They are intrinsically amorphous in nature and do not exhibit crystalline melting temperatures during thermal analysis. The effect of the fused rings on the thermal, optical, electrochemical, charge transport, and photovoltaic properties of these polymers has been investigated. The polymer (P1) containing 4,7-bis(5-bromo-4-octylthiophen-2yl)benzo[c][1,2,5] thiadiazole has a broad absorption extending from 300 to 600 nm with optical bandgaps as low as 2.02 eV. The HOMO levels (5.42 to 5.29 eV) are more sensitive to the choice of acceptor. The polymers were employed to fabricate organic photovoltaic cells with methanofullerene [6,6]-phenyl C71-butyric acid methyl ester (PC 71 BM). As a result, the polymer solar cell device containing P1 had the best preliminary results with an open-circuit voltage of 0.61 V, a short-circuit current density of 6.19 mA/cm 2 , and a fill factor of 0.32, offering an overall power conversion efficiency of 1.21%.
Dyes and Pigments, 2015
A new conjugated D-A copolymer, TBFBT, containing a fluorinated benzothiazole electron-acceptor unit and an electron-donor segment of alkylthienyl substituted thieno[2,3-f]benzofuran, was synthesized using a Stille coupling reaction. The resulting copolymer was characterized by elemental analysis, GPC, TGA, UVeVis absorption spectroscopy and cyclic voltammetry measurements. The copolymer was readily dissolved in common organic solvents, exhibited good film forming properties and displayed a broad absorption from 300 nm to 800 nm with a low optical bandgap of 1.56 eV. Cyclic voltammetry measurement gave HOMO and LUMO energy levels of À5.11 eV and À3.49 eV, respectively. Polymer solar cells based on TBFBT: PC 61 BM (1:1.5, w/w) demonstrated an initial power conversion efficiency (PCE) of 4.1% with a V oc of 0.72 V and a J sc of 11.6 mA cm À2 . PSCs based on TBFBT:PC 71 BM (1:1.5, w/w, 3 vol% 1,8diiodooctane as additive) were further optimized by using methanol. The optimized result exhibited a high PCE up to 6.1% with a high J sc of 14.4 mA cm À2 and FF of 0.62, under the illumination of AM1.5G, 100 mWcm À2 . These investigations indicate that the new copolymer TBFBT is a promising donor material for PSCs and methanol treatment is a simple and effective way to improve PCE.
Journal of Photochemistry and Photobiology A: Chemistry, 2013
After the discovery of photoinduced charge transfer in conjugated polymers, organic photovoltaic solar cells have been extensively studied due to many advantages that include flexibility and low-cost. In this context, we have synthesized a new class of conjugated polymer, poly(2-(4-{1-cyano-2-[5-(3-thiophen-2-yl-benzo[c]thiophen-1-yl)-thiophen-2-yl]-vinyl}-2,5bis-hexyloxy-phenyl)-but-2-enenitrile) (CN-PTBTBPB) for the fabrication of low cost organic solar cells. The electron donor properties of CN-PTBTBPB polymer was incorporated by means of facile Knoevenagel condensation process followed by a chemical oxidative polymerization method using oligo-5-(1-benzo[c]thiophen-3-yl)thiophene-2-carboxaldehyde with 1,4-bis(cyanomethyl) benzene linkages. The polymer was characterized by 1 H NMR and GPC techniques. The electronic and structural properties of the polymer were evaluated by UV-vis spectroscopy, fluorescence spectroscopy, and thermo gravimetric analysis. In order to establish the energy diagram of the prepared polymer, the energy gap between HOMO-LUMO was evaluated using electrochemical measurements and Density Functional Theory (DFT). The resulting CN-PTBTBPB polymer was experimentally found to possess low-lying HOMO (about −5.84 eV) and high-lying LUMO (about −3.87 eV) energy levels. This polymer exhibited a relatively wide optical band gap of ∼1.95 eV in the solid state. Using this polymer, organic photovoltaic cells were fabricated in open air of type ITO/PEDOT:PSS/CN-PTBTBPB:PCBM/Al showed promising photovoltaic properties.
Phys. Chem. Chem. Phys., 2015
Two new alkoxylphenyl substituted thieno[2,3-f ]benzofuran (TBFP)-based polymers (PTBFP-BT and PTBFP-BO) were designed and synthesized. Their structures were verified by nuclear magnetic resonance (NMR) spectroscopy, the molecular weights were determined by gel permeation chromatography (GPC) and the thermal properties were investigated by thermogravimetric analysis (TGA). The two polymers showed similar UV-Vis absorption spectra with a broad and strong absorption band from 300-750 nm in solid state. The resulting copolymers exhibited relatively deep highest occupied molecular orbital (HOMO) energy levels (À5.47 and À5.61 eV) for PTBFP-BT and PTBFP-BO, respectively. The device fabricated with PTBFP-BT : PC 71 BM showed better balanced hole and electron mobility of 2.49 Â 10 À4 cm 2 V À1 s À1 and 9.12 Â 10 À4 cm 2 V À1 s À1 , respectively, than those of PTBFP-BO based devices. The polymer solar cells (PSCs), based on the single layer device structure of ITO/PEDOT:PSS/PTBFP-BT : PC 71 BM (1 : 2, w/w)/ZrAcac/Al with 3 vol% 1,8-diiodooctane (DIO) as additive, showed a relatively high power conversion efficiency (PCE) of 6% under the illumination of AM 1.5G, 100 mW cm À2 , with a high fill factor (FF) of 0.69.
Synthesis and characterization of benzodithiophene–isoindigo polymers for solar cells
Journal of Materials Chemistry, 2012
Three new alternating polymers with the electron-deficient isoindigo group as the acceptor unit and benzo[1,2-b:4,5-b 0 ]dithiophene (BDT) or BDT flanked by thiophenes (or octylthiophenes) as the donor unit were designed and synthesized. All the polymers have good thermal stability, solubility and broad absorption spectra. Their photophysical, electrochemical and photovoltaic (PV) properties were investigated. To understand their different PV performance in the resulting polymer solar cells (PSCs), the morphology of their blends with fullerene derivatives was investigated by atomic force microscopy, and the molecular geometries as well as the molecular frontier orbitals were simulated by density functional theory calculations (Gaussian 09). The polymer PBDT-TIT, with BDT flanked by thiophenes as the donor unit and isoindigo as the acceptor unit, exhibits quite planar backbones and its blend with fullerene derivatives shows optimal morphology. As a result, the PSCs based on PBDT-TIT with a conventional device configuration of ITO/PEDOT:PSS/PBDT-TIT:PC 61 BM/LiF/Al showed a power conversion efficiency of 4.22%, with a short-circuit current density of 7.87 mA cm À2 , an opencircuit voltage of 0.79 V and a fill factor of 0.68 under the AM 1.5G illumination with an intensity of 100 mW cm À2 from a solar simulator.