A Novel Donor-Acceptor-Acceptor-Acceptor Polymer Containing Benzodithiophene and Benzimidazole-Benzothiadiazole-Benzimidazole for PSCs (original) (raw)
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The Journal of Physical Chemistry C, 2011
became attractive due to their ease of processing, formation of large areas, flexibility, and low cost. 1,2 To this end, the development of polymer solar cells has received much attention from both academic and industrial laboratories. In the past two years, great progress has been made in bulk-heterojunction (BHJ) PSCs, 3À5 but power conversion efficiency (PCE) is still a big challenge toward commercialization. To improve the PCE, it is very important to develop p-type conjugated polymers with low bandgap, high hole mobility, and deep lying HOMO energy level.
A new D−A copolymer, poly(thieno[3,2-b]thiophene-alt-bithiazole) (PTTBTz), based on thieno[3,2-b]thiophene donor unit and bithiazole acceptor unit, was synthesized by the Pd-catalyzed Stille-coupling reaction for the application as donor material in polymer solar cells (PSCs). PTTBTz film possesses high thermal stability with 5% weight-loss temperature at 450°C, a lower-lying HOMO energy level at −5.20 eV, a higher hole mobility of 6.45 × 10 −3 cm 2 /(V s), and a crystalline structure. Photovoltaic performance of the polymer was investigated with [6,6]-phenyl-C 71 -butyric acid methyl ester (PC 70 BM) or indene-C 60 bisadduct (ICBA) as acceptor and with 3% DIO additive. The power conversion efficiency (PCE) of the PSC based on PTTBTz:ICBA (1:1 w/w) reached 5.35% with a high V oc of 1.03 V, a J sc of 8.55 mA/cm 2 , and an FF of 0.608, whereas the PCE of the PSC based on PTTBTz:PC 70 BM (1:1 w/w) was 4.57% with a V oc of 0.82 V, a J sc of 9.89 mA/cm 2 , and an FF of 0.563, under the illumination of AM1.5, 100 mW/cm 2 . PTTBTz is one of the D−A copolymers that shows better photovoltaic performance with ICBA as acceptor than PC 70 BM. PTTBTz/ICBA could be a promising front active layer for high-efficiency tandem PSC because of its high V oc .
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%.
2010
A series of soluble donor-acceptor conjugated polymers comprising of phenothiazine donor and various benzodiazole acceptors (i.e., benzothiadiazole, benzoselenodiazole, and benzoxadiazole) sandwiched between hexyl-thiophene linkers were designed, synthesized, and used for the fabrication of polymer solar cells (PSC). The effects of the benzodiazole acceptors on the thermal, optical, electrochemical, and photovoltaic properties of these low-bandgap (LBG) polymers were investigated. These LBG polymers possessed large molecular weight (M n ) in the range of 3.85À5.13 Â 10 4 with high thermal decomposition temperatures, which demonstrated broad absorption in the region of 300À750 nm with optical bandgaps of 1.80À1.93 eV. Both the HOMO energy level (À5.38 to À5.47 eV) and LUMO energy level (À3.47 to À3.60 eV) of the LBG polymers were within the desirable range of ideal energy level. Under 100 mW/cm 2 of AM 1.5 white-light illumination, bulk heterojunction PSC devices containing an active layer of electron donor polymers mixed with electron acceptor [6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM) or [6,6]-phenyl-C 71butyric acid methyl ester (PC 71 BM) in different weight ratios were investigated. The best performance of the PSC device was obtained by using polymer PP6DHTBT as an electron donor and PC 71 BM as an acceptor in the weight ratio of 1:4, and a power conversion efficiency value of 1.20%, an open-circuit voltage (V oc ) value of 0.75 V, a short-circuit current (J sc ) value of 4.60 mA/cm 2 , and a fill factor (FF) value of 35.0% were achieved. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: [4823][4824][4825][4826][4827][4828][4829][4830][4831][4832][4833][4834] 2010
Synthesis of a Benzotriazole Bearing Alternating Copolymer For an Organic Photovoltaic Application
New J. Chem., 2015
A low band gap donor-acceptor (D-A) copolymer PTBTBDT, namely, poly(2-dodecyl-4,7-di(thiophen-2yl)-2H-benzo [d][1,2,3]triazole-alt-4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b 0 ]dithiophene), was designed and synthesized via a Pd-catalyzed Stille polycondensation reaction. The polymer was characterized using 1 H NMR spectroscopy, UV-vis absorption spectroscopy, cyclic voltammetry, and gel permeation chromatography (GPC). PTBTBDT has good solubility in common organic solvents, good thermal stability, broad absorption, low band gap and exhibits not only high hole mobility but also moderate photovoltaic properties. PTBTBDT displays broad absorption in the wavelength range from 300 nm to 630 nm, and its HOMO and LUMO energy levels were calculated to be À4.98 eV and À3.34 eV, respectively.
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.
ChemistrySelect 2021, Volume 6, Issue28 Pages 7025-7036, 2021
Two new wide bandgaps DÀ A copolymers compromising of same benzo [1,2-b:4, 5-b']dithiophene functionalized with thiazole side-chain donor unit and different acceptors units, i. e., fluorinated benzotriazole (FBTA) (PBDTTZ-FBTA) and bisthiophene-thieno-benzothiazole (BTZ) (PBDTTZ-BTZ) were synthesized and their optical and electrochemical properties were investigated. These copolymers exhibit appropriate frontier energy levels and complementary absorption to most middle and narrow bandgap non-fullerene small molecule non-fullerene acceptors. We have explored using these two copolymers as donors combined with a narrow bandgap non-fullerene acceptor, namely BThINDÀ Cl, for the construction of polymer solar cells. The optimized polymer solar cells employing PBDTTZ-FBTA: BThINDÀ Cl showed overall power conversion efficiency of 14.96 % (with energy loss of 0.51 eV), which is higher than that for PBDTTZ-BTZ: BThINDÀ Cl (11.68 % with energy loss of 0.56 eV). Although the PBDTTZ-BTZ exhibits a broader absorption profile than that of PBDTTZ-FBTA, the higher power conversion efficiency of the later copolymer may be correlated with the high charge carrier mobility, suppression of the bimolecular and trap-assisted recombination due to appropriate phase separation and compact π-π stacking distance in the active layer and low energy loss.