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Peng Wang - One of the best experts on this subject based on the ideXlab platform.
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high efficiency and stable dye sensitized solar cells with an organic chromophore featuring a binary π conjugated spacer
Chemical Communications, 2009Co-Authors: Guangliang Zhang, Hari Bala, Yueming Cheng, Xueju Lv, Qingjiang Yu, Peng WangAbstract:We employed a binary spacer of orderly conjugated 3,4-ethyldioxythiophene and Thienothiophene to construct a wide-spectral response organic chromophore for dye-sensitized solar cells, exhibiting a high power conversion efficiency of 9.8% measured under irradiation of 100 mW cm−2 air mass 1.5 global (AM1.5G) sunlight and an excellent stability.
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energy level and molecular engineering of organic d π a sensitizers in dye sensitized solar cells
Journal of Physical Chemistry C, 2008Co-Authors: Mingfei Xu, Nuttapol Pootrakulchote, Zhihui Yi, Shaik Mohammed Zakeeruddin, Renzhi Li, Peng WangAbstract:A series of organic D-π-A sensitizers composed of different triarylamine donors in conjugation with the Thienothiophene unit and cyanoacrylic acid as an acceptor has been synthesized at a moderate yield. Through tuning the number of methoxy substituents on the triphenylamine donor, we have gradually red-shifted the absorption of sensitizers to enhance device efficiencies. Further molecular engineering by the substitution of two hexyloxy chains in place of the methoxy groups allows fabricating a solvent-free dye-sensitized solar cell with a power conversion efficiency of 7.05% measured under the air mass 1.5 global sunlight. Time- and frequency-domain photoelectrical techniques have been employed to scrutinize the aliphatic chain effects with a close inspection on effective electron lifetime, diffusion coefficient, and diffusion length.
Manuela M. M. Raposo - One of the best experts on this subject based on the ideXlab platform.
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Push-Pull N, N-Diphenylhydrazones Bearing Bithiophene or Thienothiophene Spacers as Nonlinear Optical Second Harmonic Generators and as Photosensitizers for Nanocrystalline TiO2 Dye-Sensitized Solar Cells
'American Chemical Society (ACS)', 2018Co-Authors: Dzmitry Ivanou, Ana I. Pereira, Licínia L. G. Justino, Hugh D. Burrows, Sara S. M. Fernandes, Michael Belsley, Adélio Mendes, Manuela M. M. RaposoAbstract:A series of push-pull heterocyclic N,N-diphenylhydrazones were prepared to study the effect of structural modifications (different pi-spacers and electron-withdrawing groups) on the optical (linear and nonlinear) and lectronic properties of the molecules. The photovoltaic response of dye-sensitized solar cells assembled using nanocrystalline titania photosensitized with the synthesized dyes was also studied. These heterocyclic push-pull conjugated dyes involve N,N-diphenylhydrazones as electron donors linked to bithiophene or thieno[3,2-b]thiophene spacers and were functionalized with carboxylic acid, cyanoacetic acid, or dicyanovinyl acceptor groups. A combination of Suzuki-Miyaura cross-coupling, Vilsmeier formylation, and condensation reactions was used to synthesize the intermediates and final products. Density functional theory (DFT) and time dependent-DFT calculations were used to obtain information on conformation, electronic structure, and electron distribution, both for the free dyes and those adsorbed on TiO2. The results of this multidisciplinary study indicate that dyes 5b and 6b have the strongest second-order nonlinear optical response with hyperpolarizability values in the range of beta = 2330 X 10(-3) to 2750 X 10(-3) esu, whereas photovoltaic power conversion efficiencies reach values in the range of 0.7-3.0% for dyes 5a-b and 7c and were enhanced by coadsorbing deoxycholic acid (0.8-5.1%)
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Push–Pull N,N‑Diphenylhydrazones Bearing Bithiophene or Thienothiophene Spacers as Nonlinear Optical Second Harmonic Generators and as Photosensitizers for Nanocrystalline TiO2 Dye-Sensitized Solar Cells
2018Co-Authors: Sara S. M. Fernandes, Ana I. Pereira, Hugh D. Burrows, Adélio Mendes, Michael Belsley, Dzmitry Ivanou, Licínia L. G. Justino, Manuela M. M. RaposoAbstract:A series of push–pull heterocyclic N,N-diphenylhydrazones were prepared to study the effect of structural modifications (different π-spacers and electron-withdrawing groups) on the optical (linear and nonlinear) and electronic properties of the molecules. The photovoltaic response of dye-sensitized solar cells assembled using nanocrystalline titania photosensitized with the synthesized dyes was also studied. These heterocyclic push–pull conjugated dyes involve N,N-diphenylhydrazones as electron donors linked to bithiophene or thieno[3,2-b]thiophene spacers and were functionalized with carboxylic acid, cyanoacetic acid, or dicyanovinyl acceptor groups. A combination of Suzuki–Miyaura cross-coupling, Vilsmeier formylation, and condensation reactions was used to synthesize the intermediates and final products. Density functional theory (DFT) and time dependent-DFT calculations were used to obtain information on conformation, electronic structure, and electron distribution, both for the free dyes and those adsorbed on TiO2. The results of this multidisciplinary study indicate that dyes 5b and 6b have the strongest second-order nonlinear optical response with hyperpolarizability values in the range of β = 2330 × 10–30 to 2750 × 10–30 esu, whereas photovoltaic power conversion efficiencies reach values in the range of 0.7–3.0% for dyes 5a–b and 7c and were enhanced by coadsorbing deoxycholic acid (0.8–5.1%)
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Optical and Photovoltaic Properties of Thieno[3,2‑b]thiophene-Based Push–Pull Organic Dyes with Different Anchoring Groups for Dye-Sensitized Solar Cells
2017Co-Authors: Sara S. M. Fernandes, Ana I. Pereira, Carlos Serpa, Licínia L. G. Justino, Hugh D. Burrows, Cidália M. R. Castro, Adélio Mendes, João Pina, Manuela M. M. RaposoAbstract:The effect of anchoring groups on the optical and electrochemical properties of triphenylamine-Thienothiophenes, and on the photovoltaic performance of DSSCs photosensitized with the prepared dyes, was studied using newly synthesized compounds with cyanoacetic acid or rhodanine-3-acetic acid groups. Precursor aldehydes were synthesized through Suzuki cross-coupling, whereas Knoevenagel condensation of these with 2-cyanoacetic acid or rhodanine-3-acetic acid afforded the final push–pull dyes. A comprehensive photophysical study was performed in solution and in the solid state. The femtosecond time-resolved transient absorption spectra for the synthesized dyes were obtained following photoexcitation in solution and for the dyes adsorbed to TiO2 mesoporous films. Information on conformation, electronic structure, and electron distribution was obtained by density functional theory (DFT) and time-dependent DFT calculations. Triphenylamine–Thienothiophene functionalized with a cyanoacetic acid anchoring group displayed the highest conversion efficiency (3.68%) as the dye sensitizer in nanocrystalline TiO2 solar cells. Coadsorption studies were performed for this dye with the ruthenium-based N719 dye, and they showed dye power conversion efficiencies enhanced by 20–64%. The best cell performance obtained with the coadsorbed N719 and cyanoacetic dye showed an efficiency of 6.05%
Bongsoo Kim - One of the best experts on this subject based on the ideXlab platform.
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photoresponsive transistors based on a dual acceptor containing low bandgap polymer
ACS Applied Materials & Interfaces, 2017Co-Authors: Min Je Kim, Shinyoung Choi, Myeongjae Lee, Hyojung Heo, Youngu Lee, Jeong Ho Cho, Bongsoo KimAbstract:In this Article, low-bandgap pTTDPP-BT polymers based on electron-accepting pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) and benzothiadiazole (BT) and electron-donating Thienothiophene (TT) moieties were synthesized. Phototransistors have been fabricated using ambipolar-behaving pTTDPP-BT polymers as active channel materials. The electrical and photoresponsive properties of the pTTDPP-BT phototransistors were strongly dependent on the film annealing temperature. As-spun pTTDPP-BT phototransistors exhibited a low hole mobility of 0.007 cm2/(V·s) and a low electron mobility of 0.005 cm2/(V·s), which resulted in low photocurrent detection due to the limited transport of the charge carriers. Thermal treatment of the polymer thin films led to a significant enhancement in the carrier mobilities (hole and electron mobilities of 0.066 and 0.115 cm2/(V·s), respectively, for 200 °C annealing) and thus significantly improved photoresponsive properties. The 200 °C-annealed phototransistors showed a wide-range wavelen...
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Photoresponsive Transistors Based on a Dual Acceptor-Containing Low-Bandgap Polymer
2017Co-Authors: Min Je Kim, Shinyoung Choi, Myeongjae Lee, Hyojung Heo, Youngu Lee, Jeong Ho Cho, Bongsoo KimAbstract:In this Article, low-bandgap pTTDPP-BT polymers based on electron-accepting pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) and benzothiadiazole (BT) and electron-donating Thienothiophene (TT) moieties were synthesized. Phototransistors have been fabricated using ambipolar-behaving pTTDPP-BT polymers as active channel materials. The electrical and photoresponsive properties of the pTTDPP-BT phototransistors were strongly dependent on the film annealing temperature. As-spun pTTDPP-BT phototransistors exhibited a low hole mobility of 0.007 cm2/(V·s) and a low electron mobility of 0.005 cm2/(V·s), which resulted in low photocurrent detection due to the limited transport of the charge carriers. Thermal treatment of the polymer thin films led to a significant enhancement in the carrier mobilities (hole and electron mobilities of 0.066 and 0.115 cm2/(V·s), respectively, for 200 °C annealing) and thus significantly improved photoresponsive properties. The 200 °C-annealed phototransistors showed a wide-range wavelength (405–850 nm) of photoresponse, and a high photocurrent/dark-current ratio of 150 with a fast photoswitching speed of less than 100 ms. This work demonstrates that a dual acceptor-containing low band gap polymer can be an important class of material in broadband photoresponsive transistors, and the crystallinity of the semiconducting polymer layer has a significant effect on the photoresponse characteristics
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importance of solubilizing group and backbone planarity in low band gap polymers for high performance ambipolar field effect transistors
Chemistry of Materials, 2012Co-Authors: Joong Suk Lee, Donghoon Choi, Bongsoo Kim, Seon Kyoung Son, Sanghoon Song, Hyunjung Kim, Dong Ryoul Lee, Kyungkon Kim, Jeong Ho ChoAbstract:We investigated the performance of ambipolar field-effect transistors based on a series of alternating low band gap polymers of oligothiophene and diketopyrrolopyrrole (DPP). The polymers contain oligothiophene units of terthiophene [T3] and thiophene-Thienothiophene-thiophene [T2TT] and DPP units carrying branched alkyl chains of 2-hexyldecyl [HD] or 2-octyldodecyl [OD]. The structural variation allows us to do a systematic study on the relationship between the interchain stacking/ordering of semiconducting polymers and their resulting device performance. On the basis of synchrotron X-ray diffraction and atomic force microscopy measurements on polymer films, we found that longer branched alkyl side chains, i.e., OD, and longer and more planar oligothiophene, i.e., T2TT, generate the more crystalline structures. Upon thermal annealing, the crystallinity of the polymers was largely improved, and polymers containing a longer branched alkyl chain responded faster because longer alkyl chains have larger cohes...
Yongye Liang - One of the best experts on this subject based on the ideXlab platform.
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synthesis of fluorinated polyThienothiophene co benzodithiophenes and effect of fluorination on the photovoltaic properties
Journal of the American Chemical Society, 2011Co-Authors: Hae Jung Son, Wei Wang, Yongye LiangAbstract:Herein, we describe the synthesis of fluorinated polyThienothiophene-co-benzodithiophenes (PTBFs) and the characterization of their physical properties, especially their performance in solar cells. Fluorination of the polymer backbone lowered both the HOMO and LUMO energy levels and simultaneously widened the energy bandgap of the polymer (0.1−0.2 eV). Incorporation of fluorine into the various positions of the polymer backbone significantly affected the solar cells’ power conversion efficiency from 2.3% to 7.2%. Detailed studies revealed that the polymer containing mono-fluorinated Thienothiophene gave the best solar cell performance. Perfluorination of the polymer backbone led to poor compatibility with PC71BM molecules, thus poor solar energy conversion efficiency. This is possibly due to the enhanced self-organization properties of the polymer chains and the fluorophobicity effect. Furthermore, it was found that perfluorination of the polymer backbone resulted in poor photochemical stability against s...
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structure dynamics and power conversion efficiency correlations in a new low bandgap polymer pcbm solar cell
Journal of Physical Chemistry B, 2010Co-Authors: Jianchang Guo, Yongye Liang, Hae Jung Son, Jodi M Szarko, Byeongdu Lee, Brian S Rolczynski, Lin X ChenAbstract:Molecular packing structures and photoinduced charge separation dynamics have been investigated in a recently developed bulk heterojunction (BHJ) organic photovoltaic (OPV) material based on poly(Thienothiophene-benzodithiophene) (PTB1) with a power conversion efficiency (PCE) of >5% in solar cell devices. Grazing incidence X-ray scattering (GIXS) measurements of the PTB1:PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) films revealed π-stacked polymer backbone planes oriented parallel to the substrate surface, in contrast to the π-stacked polymer backbone planes oriented perpendicular to the substrate surface in regioregular P3HT [poly(3-hexylthiophene)]:PCBM films. A ∼1.7 times higher charge mobility in the PTB1:PCBM film relative to that in P3HT:PCBM films is attributed to this difference in stacking orientation. The photoinduced charge separation (CS) rate in the pristine PTB1:PCBM film is more than twice as fast as that in the annealed P3HT:PCBM film. The combination of a small optical gap, fast CS ...
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plastic near infrared photodetectors utilizing low band gap polymer
Advanced Materials, 2007Co-Authors: Yan Yao, Yongye Liang, Vishal Shrotriya, Shengqiang Xiao, Yang YangAbstract:Organic photodetectors (PDs) have been the subject of extensive research in the past decade due to several inherent advantages: large-area detection, wide selection of materials, and low-cost fabrication on flexible substrates. High external quantum efficiency (EQE), full-color, fast-response, and position-sensitive PDs have been reported in the past. However, there are few reports on organic near-infrared photodetectors (NIR-PDs) in spite of their tremendous potential in industrial and scientific applications, such as remote control, chemical/biological sensing, optical communication, and spectroscopic and medical instruments. S. Meskers and co-workers reported an infrared PD in which doped poly(2, 4-ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) was used as the active material. More recently, G. Konstantatos and coworkers fabricated NIR-PDs by spin-coating colloidal quantum dots from solution onto gold interdigitated electrodes. The device showed a large photoconductive gain and high detectivity at 1.3 lm. However, 3-dB bandwidth was only about 18 Hz and the working voltage was as high as 40 V. These characteristics strongly restrict their applications in the fields of imaging and communication where high-speed and low-power PDs are desired. Thus, there is a strong need for the development of fast response and low working voltage NIR-PDs while simultaneously maintaining the benefit of low-cost solution process. Here we report an organic near-infrared photodetector using a new low band gap polymer. By utilizing an ester group modified polythieno[3,4-b]thiophene, we have successfully lowered the highest occupied molecular orbital (HOMO) energy level of the low band gap (LBG) polymer, so that it can match the energy level of (6,6)-phenyl C61-butyric acid methyl ester (PCBM), and has good solubility and easy processing ability. In this communication, we report a device which has a donoracceptor type energy structure whose operation shows excellent NIR detection capability. Reports on LBG polymers for solar energy conversion have emerged recently. The preparation of LBG, high mobility, solution-processable polymers is not trivial and requires judicious design. Among several band gap tuning strategies for conjugated polymers, polymerization of fused heterocyclic rings has been known to yield polymers with very low band gaps. Polythieno[3,4-b]thiophene (PTT) is one kind of LBG polymers in which the fused thiophene moieties can stabilize the quinoid structure of the backbone, thereby reducing the band gap of the conjugated system. Several PTTs without side chains have been reported previously, but the poor solubility makes them difficult to process and limits their use in electro-optical and electronic devices. Synthesis of alkyl chains substituted thieno[3,4-b]thiophenes monomers have been reported and the resulting polymers exhibit better solubility, but poor oxidative stability. It was found that the HOMO levels of these polymers are too high to match the energy levels of the commonly used electron acceptor, PCBM. We report a new type of ester group modified PTT polymer (Scheme 1). The introduction of an ester group at the 2-position of thieno[3,4-b]thiophene has two effects. First, the electron withdrawing ester group can stabilize the electron-rich Thienothiophene and lower the HOMO energy level of the polymer to match the energy level of PCBM. Second, a long tertiary alkyl side chain from the ester group can increase the solubility of the polymer. Polymer was synthesized by Stille polycondensation reaction between the bisbrominated thieno[3,4-b]thiophene and bis-stannylated thiophene. (Scheme 1; see Supporting Information for details) The resulting polymer has good solubility in chloroform and chlorobenzene. In contrast to inorganic semiconductors, photoexcitation of organic semiconductors generates strong bound excitons rather than free charge carriers. To dissociate excitons efficiently, the donor/acceptor bulk heterojunction approach is typically used. The active layer in our PD comprises of PTT and PCBM (Fig. 1a), forming interpenetrating donor/acceptor networks. Details of the device fabrication process are given in the Experimental section. Figure 1b shows the absorption spectra of PTT and PTT: PCBM films. Pure PTT thin film abC O M M U N IC A IO N
Jeong Ho Cho - One of the best experts on this subject based on the ideXlab platform.
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photoresponsive transistors based on a dual acceptor containing low bandgap polymer
ACS Applied Materials & Interfaces, 2017Co-Authors: Min Je Kim, Shinyoung Choi, Myeongjae Lee, Hyojung Heo, Youngu Lee, Jeong Ho Cho, Bongsoo KimAbstract:In this Article, low-bandgap pTTDPP-BT polymers based on electron-accepting pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) and benzothiadiazole (BT) and electron-donating Thienothiophene (TT) moieties were synthesized. Phototransistors have been fabricated using ambipolar-behaving pTTDPP-BT polymers as active channel materials. The electrical and photoresponsive properties of the pTTDPP-BT phototransistors were strongly dependent on the film annealing temperature. As-spun pTTDPP-BT phototransistors exhibited a low hole mobility of 0.007 cm2/(V·s) and a low electron mobility of 0.005 cm2/(V·s), which resulted in low photocurrent detection due to the limited transport of the charge carriers. Thermal treatment of the polymer thin films led to a significant enhancement in the carrier mobilities (hole and electron mobilities of 0.066 and 0.115 cm2/(V·s), respectively, for 200 °C annealing) and thus significantly improved photoresponsive properties. The 200 °C-annealed phototransistors showed a wide-range wavelen...
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Photoresponsive Transistors Based on a Dual Acceptor-Containing Low-Bandgap Polymer
2017Co-Authors: Min Je Kim, Shinyoung Choi, Myeongjae Lee, Hyojung Heo, Youngu Lee, Jeong Ho Cho, Bongsoo KimAbstract:In this Article, low-bandgap pTTDPP-BT polymers based on electron-accepting pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) and benzothiadiazole (BT) and electron-donating Thienothiophene (TT) moieties were synthesized. Phototransistors have been fabricated using ambipolar-behaving pTTDPP-BT polymers as active channel materials. The electrical and photoresponsive properties of the pTTDPP-BT phototransistors were strongly dependent on the film annealing temperature. As-spun pTTDPP-BT phototransistors exhibited a low hole mobility of 0.007 cm2/(V·s) and a low electron mobility of 0.005 cm2/(V·s), which resulted in low photocurrent detection due to the limited transport of the charge carriers. Thermal treatment of the polymer thin films led to a significant enhancement in the carrier mobilities (hole and electron mobilities of 0.066 and 0.115 cm2/(V·s), respectively, for 200 °C annealing) and thus significantly improved photoresponsive properties. The 200 °C-annealed phototransistors showed a wide-range wavelength (405–850 nm) of photoresponse, and a high photocurrent/dark-current ratio of 150 with a fast photoswitching speed of less than 100 ms. This work demonstrates that a dual acceptor-containing low band gap polymer can be an important class of material in broadband photoresponsive transistors, and the crystallinity of the semiconducting polymer layer has a significant effect on the photoresponse characteristics
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importance of solubilizing group and backbone planarity in low band gap polymers for high performance ambipolar field effect transistors
Chemistry of Materials, 2012Co-Authors: Joong Suk Lee, Donghoon Choi, Bongsoo Kim, Seon Kyoung Son, Sanghoon Song, Hyunjung Kim, Dong Ryoul Lee, Kyungkon Kim, Jeong Ho ChoAbstract:We investigated the performance of ambipolar field-effect transistors based on a series of alternating low band gap polymers of oligothiophene and diketopyrrolopyrrole (DPP). The polymers contain oligothiophene units of terthiophene [T3] and thiophene-Thienothiophene-thiophene [T2TT] and DPP units carrying branched alkyl chains of 2-hexyldecyl [HD] or 2-octyldodecyl [OD]. The structural variation allows us to do a systematic study on the relationship between the interchain stacking/ordering of semiconducting polymers and their resulting device performance. On the basis of synchrotron X-ray diffraction and atomic force microscopy measurements on polymer films, we found that longer branched alkyl side chains, i.e., OD, and longer and more planar oligothiophene, i.e., T2TT, generate the more crystalline structures. Upon thermal annealing, the crystallinity of the polymers was largely improved, and polymers containing a longer branched alkyl chain responded faster because longer alkyl chains have larger cohes...