Tuning the Band Gap of Low-Band-Gap Polyselenophenes and Polythiophenes: The Effect of the Heteroatom † (original) (raw)
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2018
In this study, two donor-acceptor (D-A) type conjugated polymers namely PQSeCz and PQSeFl were designed and synthesized. Selenophene was incorporated as a π -bridge, quinoxaline as an acceptor unit while carbazole and fluorene were used as the donor units. Polymers were synthesized via palladium catalyzed Suzuki polymerization reaction. All molecules were characterized by 1H and 13C NMR Spectroscopy. The weight and number average molecular weights of the two polymers were determined by gel permeation chromatography (GPC). Electrochemical and spectroelectrochemical characterizations of the polymers were performed to investigate their optoelectronic properties. Oxidation potentials were 1.15 V/ 0.82 V and 1.11 V/ 0.82 V for PQSeCz and PQSeFl respectively, while reduction potentials were -1.26 V /-1.14 V and -1.48 V/ -1.23 V, respectively. In the visible region, maximum absorption wavelengths for the two polymers were 551 nm and 560 nm, respectively. Optical band gaps (Egop) were fo...
Polymer Bulletin, 2019
In this study, two donor-acceptor (D-A) type conjugated polymers namely PQSeCz and 15 PQSeFl were designed and synthesized. Selenophene was incorporated as a π-bridge, quinoxaline 16 as an acceptor unit while carbazole and fluorene were used as the donor units. Polymers were 17 synthesized via palladium catalyzed Suzuki polymerization reaction. All molecules were 18 characterized by 1 H and 13 C NMR Spectroscopy. The weight and number average molecular weights 19 of the two polymers were determined by gel permeation chromatography (GPC). Electrochemical 20 and spectroelectrochemical characterizations of the polymers were performed to investigate their 21 optoelectronic properties. Oxidation potentials were 1.15 V/ 0.82 V and 1.11 V/ 0.82 V for PQSeCz 22 and PQSeFl respectively, while reduction potentials were-1.26 V /-1.14 V and-1.48 V/-1.23 V, 23 respectively. In the visible region, maximum absorption wavelengths for the two polymers were 551 24 nm and 560 nm, respectively. Optical band gaps (Eg op) were found from the lowest energy π-π * 25 transition onsets as 1.71 eV and 1.58 eV, respectively. Both polymers showed good solubility in 26 common solvents. 27
Molecular architecture: Another plausible pathway toward a low band gap polymer
Journal of Electroanalytical Chemistry, 2010
A donor-acceptor-donor p-conjugated monomer (10,13-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5yl)dibenzo[a,c]phenazine (PHED)) composed of bi-EDOT and dibenzo[a,c]phenazine repeat units was synthesized to examine the role of acceptor structure on the electronic and optoelectronic properties of the polymer. The spectroelectrochemical analysis showed that the introduction of electron-accepting unit results in a shift in the onset of the p-p à transition towards longer wavelengths. The optical band gap (Eg) for PPHED was found to be 1.10 eV and k max was 790 nm. Switching ability of PPHED was evaluated by kinetic studies via measuring the percent transmittance as 80% at 1600 nm. The high optical contrast within the NIR region makes this material a good candidate for NIR device applications. Dual-type complementary colored electrochromic devices (ECD) using PPHED/PEDOT in sandwich configuration were constructed. Spectroelectrochemistry, switching ability and open circuit memory of the ECDs were investigated.
Solar Energy Materials and Solar Cells, 2016
An approach to improve the efficiency of donor-acceptor based bulk heterojunction (BHJ) organic solar cells is the use of low band gap (LBG) polymers as donor materials. The properties of these materials in BHJ solar cells are strongly influenced by their morphology and ability for self-organization in thin-films. We studied for two related polymer pairs the influence of the introduction of additional (hexyl-) thiophene moieties on both the electronic structure and ability for self-organization in thin films using Ultraviolet photoelectron spectroscopy (UPS) and Near-Edge X-Ray Absorption Fine Structure spectroscopy (NEXAFS). In addition, the influence of mixing with PCBM and post-processing annealing on the molecular orientation is investigated. We find that the introduction of additional (hexyl-) thiophene moieties in the polymer structure does not affect significantly the electronic structure of the polymers in thin films, but has a strong impact on their self-organization properties and consequently affects their behavior in devices.
Journal of Materials Chemistry, 2004
Scheme 1 a) NaH/THF, 3 h, then C 10 H 21 Br, reflux, 3 d. b) n-BuLi/ THF, 270 to 220 uC, 2 h, then Bu 3 SnCl, 270 to 0 uC, 12 h. c) 1 eq NBS/DMF, 0 uC, 3.5 h. d) 5, PdCl 2 (PPh 3 ) 2 , toluene, 90 uC, 16 h.
Synthetic Metals, 2003
To enhance the efficiency of polymer photovoltaics, much effort is put into synthesis of novel compounds which show a better harvesting of solar light. In this respect, a new low band gap polymer, namely, poly(5,6-dithiooctylisothianaphtene), was synthesised. This work focusses on the spectroscopic characterisation of the material. The dynamics of the photoexcitations were studied by monitoring the dependence of the photoinduced absorption band on the laser modulation frequency and indicated dispersive recombination kinetics in this material. An appropriate model was used to describe the observed behaviour. To investigate the nature of the photogenerated species more profound, photoinduced absorption spectroscopy in the infrared was performed, showing an infrared active vibrational pattern (IRAV). Solar cells were constructed with an active layer consisting of the pristine material or a mixture with an electron accepting moiety. For this purpose, (6,6)phenyl-C 61 -butyric-acid (PCBM) in 1:1 a (w/w) ratio with respect to the polymer was used. A clear improvement of the diode behaviour was observed going from the pristine material to the mixture. Photocurrent action spectra of the solar cells with the polymer:PCBM-mixture indicated an active contribution of the polymer to the photocurrent. #