Synthesis and photovoltaic properties of two new alkoxylphenyl substituted thieno[2,3-f]benzofuran based polymers (original) (raw)
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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 Materials Chemistry, 2012
Two benzo[1,2-b:4,5-b 0 ]dithiophene (BDT) derivatives with conjugated substituents, triisopropylsilylethynyl (TIPS) and 4-octylphenylethynyl groups, were synthesized as donor units (D) and copolymerized with two acceptor units (A), 4,7-bis(4-octylthiophen-2-yl)-2,1,3-benzothiadiazole (BT) and 4,4 0 -diundecyl-2,2 0 -bithiazole (BTZ), respectively, using Stille coupling reaction to afford four new copolymers, PTBDT-BT, PTBDT-BTZ, POPEBDT-BT, POPEBDT-BTZ. All polymers exhibited highest occupied molecular orbital (HOMO) energy levels that were deeper than À5.4 eV due to the conjugated substituents. Small band gaps were successfully achieved for PTBDT-BT (1.67 eV) and POPEBDT-BT (1.67 eV) and were attributable to the strong intramolecular charge transfer within the D-A alternating structure. The resultant photovoltaic performances showed high open-circuit voltages (V oc ) ranging from 0.73 V to 0.92 V, whereas the power conversion efficiencies (PCEs) depended strongly on the blend morphologies. The polymer solar cell based on the blend of PTBDT-BT and PC 71 BM gave the best photovoltaic performance among the series, with a high V oc of 0.81 V and a PCE of 4.61%.
Polymer Chemistry, 2014
A new low bandgap D-A copolymer PBDFTDTBT containing 4,8-bis(2-(2-ethylhexyl)thiophen-2-yl)-benzo [1,2-b;3,4-b 0 ]difuran (BDFT) and 4,7-di(thiophen-2-yl)-5,6-dioctyloxybenzo[c][1,2,5]thiadiazole (DTBT) units was synthesized and characterized for application as a donor material in polymer solar cells (PSCs). The PBDFTDTBT film showed a broad absorption band from 300 nm to around 730 nm in the visible light region and the hole mobility of the blend of PBDFTDTBT and PC 71 BM reached up to 0.36 cm 2 V À1 s À1 by using the space charge limited current (SCLC) method. The PSCs based on PBDFTDTBT:PC 71 BM (1 : 1.5, w/w) exhibited a promising power conversion efficiency (PCE) of 6.0% under the illumination of AM 1.5 G, 100 mW cm À2 with a high short circuit current density (J sc ) of 12.04 mA cm À2 and an open circuit voltage (V oc ) of 0.76 V.
Polymers, 2017
Novel two-dimensional conjugated copolymer, abbreviated as PDTBSeVTT-2TF, containing electron-deficient 4,7-di(thiophen-2-yl)benzo[c][1,2,5]selenodiazole (DTBSe) unit, conjugated vinyl-terthiophene (VTT) side chain and 3,3-difluoro-2,2-bithiophene (2TF) was designed and synthesized using microwave-assisted Stille cross-coupling polymerization. UV-visible absorption and cyclic voltammetry studies revealed that this copolymer possesses a strong and broad absorption in the range of 300-800 nm and a narrow optical bandgap (E g) of 1.57 eV with low-lying HOMO and LUMO energy levels. Further, the bulk heterojunction polymer solar cells (PSCs) were fabricated using PDTBSeVTT-2TF as donor and [6,6]-phenyl-C 71-butyric acid methyl ester (PC 71 BM) as acceptor with an inverted device structure of ITO/ZnO/PDTBSeVTT-2TF:PC 71 BM/V 2 O 5 /Ag. The processing temperature of blend solution for preparing PDTBSeVTT-2TF:PC 71 BM active layer showed obvious impact on the photovoltaic performance of solar devices. The cell fabricated from the blend solution at 65 • C exhibited enhanced power conversion efficiencies (PCE) of 5.11% with a J sc of 10.99 mA/cm −2 compared with the one at 50 • C, which had a PCE of 4.69% with a J sc of 10.10 mA/cm −2. This enhancement is due to the dissolution of PDTBSeVTT-2TF clusters into single molecules and small aggregates, improving the miscibility between the polymer and PC 71 BM and thus increasing the donor/acceptor interface.
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%.
Design, synthesis and photovoltaic properties of a new D–π–A polymer with extended π-bridge units
Journal of Materials Chemistry, 2012
New low band gap copolymers PBDTT-DTTBT and PBDTT-DTBT using BDT-T and BT as donor and acceptor, with different p-bridge units thieno [3,2-b]thiophene and thiophene, respectively, were synthesized. The absorption spectra, electronic energy levels, and photovoltaic properties of the polymers were characterized. PBDTT-DTTBT and PBDTT-DTBT films show broad absorption in the visible range with an absorption edge at over 751 nm, and possess relatively low-lying HOMO levels at À5.11 eV and 5.15 eV. A high hole mobility of 1.97 Â 10 À3 cm 2 V À1 s À1 was recorded for PBDTT-DTTBT, that is two orders of magnitude higher than PBDTT-DTBT (1.58 Â 10 À5 cm 2 V À1 s À1 ), which is ascribed to the application of thieno[3,2-b]thiophene as p-bridge units. The PCE of the PSC device based on PBDTT-DTTBT/PC 70 BM (1 : 1, w/w) reached 6.03% with a J sc of 12.46 mA cm À2 , a V oc of 0.78 V and a FF of 0.62, while PBDTT-DTBT/PC 70 BM (1 : 1, w/w) only has a PCE of 2.34% with a V oc of 0.82 V, a J sc of 5.78 mA cm À2 and a FF of 0.495 under the illumination of AM 1.5 G, 100 mW cm À2 . These results indicate that PBDTT-DTTBT is a promising photovoltaic material. Furthermore, it can be concluded that extending the conjugation of the backbone units, as demonstrated in this work, has little influence on the molecular energy levels, but can be seen as a feasible strategy to improve the photovoltaic properties of D-p-A conjugated polymers by enhancing intermolecular interactions.
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.
ACS applied materials & interfaces, 2015
Two new small molecules, C3T-BDTP and C3T-BDTP-F with alkoxyphenyl-substituted benzo[1,2-b:4,5-b']dithiophene (BDT) and meta-fluorinated-alkoxyphenyl-substituted BDT as the central donor blocks, respectively, have been synthesized and used as donor materials in organic solar cells (OSCs). With the addition of 0.4% v/v 1,8-diiodooctane (DIO), the blend of C3T-BDTP-F/PC71BM showed a higher hole mobility of 8.67 × 10(-4) cm(2) V(-1) s(-1) compared to that of the blend of C3T-BDTP/PC71BM. Two types of interlayers, zirconium acetylacetonate (ZrAcac) and perylene diimide (PDI) derivatives (PDINO and PDIN), were used to further optimize the performance of OSCs. With a device structure of ITO/PEDOT:PSS/donor:PC71BM/PDIN/Al, the OSCs based on C3T-BDTP delivered a satisfying power conversion efficiency (PCE) of 5.27% with an open circuit voltage (Voc) of 0.91 V, whereas the devices based on C3T-BDTP-F showed an enhanced PCE of 5.42% with a higher Voc of 0.97 V.
Advancement in P3HT PCBM solar cells, the most efficient Polymer Photovoltaic cell
Concern about global warming and diminishing fossil fuel reserves have accelerated searches for low cost sources of renewable energy. Organic photovoltaic (OPV) cells are one such source. They have couple of advantages over the conventional semiconductors. Organic solar cells have the potential to be low cost and efficient solar energy convertors, with a promising energy balance. The applications of thermoelectric polymers at low temperatures, especially conducting polymers, have shown various advantages such as easy and low cost of fabrication, light weight, and flexibility. However efficiency remains quite low. Thus efforts have been made to increase the efficiency by varying the fabrication parameters. Poly (3-hexythiophene) (P3HT) and 1-(3-methoxycarbonyl) propyl-1-phenyl [6, 6] C 61 (PCBM) are the most studied polymer blend materials around the world for bulk heterojunction structure of an organic solar cells (OSCs). This research article is a survey on tremendous literature published that exhibit solar cells based on blends of P3HT and PCBM. The basic structure of a P3HT: PCBM heterojunction solar cell and accurate methods for measurement of the power conversion efficiency (PCE) were also discussed. Standard method using Air Mass 1.5 Global (1000Wm -2 , AM1.5G) solar spectrum is advised after finding abnormalities in the PCE reported. It is noticed that optimum thickness and area of every layer in the cell structure is important. A detailed discussion on thermal annealing and solvent annealing approaches to improve device performance is presented. The effects of these two approaches on improving polymer crystallinity, light absorption in the polymer, carrier transport, and blend film nano-morphology, etc. are summarized. Polymer morphology has proven to be extremely important in determining the optoelectronic properties in polymer-based devices. We also investigate the effects of polymer morphology too on the PCE of the cell. Another important parameter affecting the efficiency discussed is the Molecular weight ratio of P3HT and PCBM blend active layer. Future directions and challenges on polymer solar cell development are also discussed Keywords— P3HT: PCBM organic blend layer, Polymer Photovoltaic, Organic solar cells, bulk heterojunctions.