| 61. |
- Musumeci, Chiara, et al.
(författare)
-
Organic electrochemical transistors from supramolecular complexes of conjugated polyelectrolyte PEDOTS
- 2019
-
Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 7:10, s. 2987-2993
-
Tidskriftsartikel (refereegranskat)abstract
- Counterion exchange strategies are used to modify the hydrophilic character of the self-doped conjugated polyelectrolyte PEDOTS. The supramolecular complexes, soluble in organic solvents, are suitable to fabricate finely performing thin active layers in organic electrochemical transistors (OECTs). We demonstrate that ionic transport in these PEDOTS based complexes, thus their performance in OECT devices, is governed by a delicate balance among degree of doping, wettability and porosity, which can be controlled by a precise tuning of the polyelectrolyte/hydrophobic counterion ratio. We also show that the device operation can be modulated by varying the composition of the aqueous electrolyte in a range compatible with biological processes, making these materials suitable candidates to be interfaced with living cells.
|
|
| 62. |
- Ouyang, Liangqi, et al.
(författare)
-
Imaging the Phase Separation Between PEDOT and Polyelectrolytes During Processing of Highly Conductive PEDOT:PSS Films
- 2015
-
Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 7:35, s. 19764-19773
-
Tidskriftsartikel (refereegranskat)abstract
- Treating PEDOT:PSS (Clevios) with certain additives, such as ethylene glycol (EG), dimethyl sulfoxide (DMSO) and sorbitol, has been shown to increase the conductivity of this material from roughly 1 to nearly 1000 S/cm. Using a slow drying method, we show that the additive induced a separation between free PSS and reorganized PEDOT:PSS complexes in the highly conductive PEDOT:PSS films. Additives (DMSO, DEG, and PEG 400) were included in PEDOT:PSS aqueous dispersions at large volume fractions. The mixtures were slowly dried under room conditions. During drying, the evaporation of water resulted in an additive-rich solvent mixture from which the reorganized PEDOT:PSS complexes aggregated " into a dense film while free PSS remained in the solution. Upon complete drying, PSS formed a transparent rim film around the conducting PEDOT film. The chemical compositions of the two phases were studied using an infrared microscope. This removal of PSS resulted in more compact packing of PEDOT molecules, as confirmed by X-ray diffraction measurements. X-ray photoelectron spectroscopy and atomic force microscope measurements suggested the enrichment of PEDOT on the film surface after PSS separation. Through a simple drying process in an additive-containing dispersion, the conductivity of PEDOT films increased from 0.1 to 200-400 S/cm. Through this method, we confirmed the existence of two phases in additive-treated and highly conductive PEDOT:PSS films. The proper separation between PSS and PEDOT will be of relevance in designing strategies to process high-performance plastic electrodes.
|
|
| 63. |
- Ouyang, Liangqi, et al.
(författare)
-
The contraction of PEDOT films formed on a macromolecular liquid-like surface
- 2018
-
Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 6:3, s. 654-660
-
Tidskriftsartikel (refereegranskat)abstract
- Vapour phase polymerized (VPP) PEDOT obtained using triblock copolymer PEG-PPG-PEG: Fe(III) tosylate polymeric oxidative layers has shown record-high conductivity and unique thermoelectric properties. These properties are related to the molecular weight, morphology and doping of PEDOT. Here we show that in its unwashed condition, the PEDOT chain adopts a neutral benzenoid conformation. The polymer chain converts into the charged quinoid structure after the removal of oxidizers with solvent washing. X-ray diffraction results suggest that the dopant is also incorporated into the packed polymer after the washing process. The changes in the chain structure and doping lead to the characteristic polaron and bipolaron absorption in the 800 and 1200 nm range. We observed a large contraction of the film after washing that is likely due to these changes, along with the removal of excessive polymer: oxidizer trapped in the PEDOT matrix. The contraction of films can be completely suppressed by mechanical clamping. PEDOT films without contraction show both a higher conductivity and higher optical transparency.
|
|
| 64. |
- Patil, Nagaraj, et al.
(författare)
-
Bioinspired Redox-Active Catechol-Bearing Polymers as Ultrarobust Organic Cathodes for Lithium Storage
- 2017
-
Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 29:40
-
Tidskriftsartikel (refereegranskat)abstract
- Redox-active catechols are bioinspired precursors for ortho-quinones that are characterized by higher discharge potentials than para-quinones, the latter being extensively used as organic cathode materials for lithium ion batteries (LIBs). Here, this study demonstrates that the rational molecular design of copolymers bearing catechol-and Li+ ion-conducting anionic pendants endow redox-active polymers (RAPs) with ultrarobust electrochemical energy storage features when combined to carbon nanotubes as a flexible, binder-, and metal current collector-free buckypaper electrode. The importance of the structure and functionality of the RAPs on the battery performances in LIBs is discussed. The structure-optimized RAPs can store high-capacities of 360 mA h g(-1) at 5C and 320 mA h g(-1) at 30C in LIBs. The high ion and electron mobilities within the buckypaper also enable to register 96 mA h g(-1) (24% capacity retention) at an extreme C-rate of 600C (6 s for total discharge). Moreover, excellent cyclability is noted with a capacity retention of 98% over 3400 cycles at 30C. The high capacity, superior active-material utilization, ultralong cyclability, and excellent rate performances of RAPs-based electrode clearly rival most of the state-of-the-art Li+ ion organic cathodes, and opens up new horizons for large-scalable fabrication of electrode materials for ultrarobust Li storage.
|
|
| 65. |
- Ponseca, Carlito, et al.
(författare)
-
Pulsed Terahertz Emission from Solution-Processed Lead Iodide Perovskite Films
- 2019
-
Ingår i: ACS Photonics. - : AMER CHEMICAL SOC. - 2330-4022. ; 6:5, s. 1175-1181
-
Tidskriftsartikel (refereegranskat)abstract
- We report pulsed terahertz (THz) emission from solution-processed metal halide perovskite films with electric field 1 order of magnitude lower than p-InAs, an efficient THz emitter. Such emission is enabled by a unique combination of efficient charge separation, high carrier mobilities, and more importantly surface defects. The mechanism of generation was identified by investigating the dependence of the THz electric field amplitude on surface defect densities, excess charge carriers, excitation intensity and energy, temperature, and external electric field. We also show for the first time THz emission from a curved surface, which is not possible for any crystalline semiconductor and paves the way to focus high-intensity sources. These results represent a possible new direction for perovskite optoelectronics and for THz emission spectroscopy as a complementary tool in investigating surface defects on metal halide perovskites, of fundamental importance in the optimization of solar cells and light-emitting diodes.
|
|
| 66. |
- Ponseca, Carlito, et al.
(författare)
-
Terahertz Helical Antenna Based on Celery Stalks
- 2019
-
Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - : IEEE Computer Society. - 9781538682852 - 9781538682869
-
Konferensbidrag (refereegranskat)abstract
- Cellulose-based helices retrieved from the plant celery with a conductive poly(4-(2,3-dihydrothieno [3,4-b]-[1,4]dioxin-2-yl-methoxy)-1-butanesulfonate (PEDOT-S). A resonance close to 1 THz and a broad shoulder that extends to 3.5 THz was obtained, consistent with electromagnetic models. As helical antennas, it was shown that both axial and normal modes are present, which are correlated to the orientation and antenna electrical lengths of the coated helices. This work opens the possibility of designing tunable terahertz antennas through simple control of their dimensions and orientation. © 2019 IEEE.
|
|
| 67. |
- Puttisong, Yuttapoom, et al.
(författare)
-
Charge Generation via Relaxed Charge-Transfer States in Organic Photovoltaics by an Energy-Disorder-Driven Entropy Gain
- 2018
-
Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 122:24, s. 12640-12646
-
Tidskriftsartikel (refereegranskat)abstract
- In organic photovoltaics, efficient charge generation relies on our ability to convert excitons into free charges. Efficient charge separation from "energetic excitons" has been understood to be governed by delocalization effects promoted by molecular aggregation. A remaining puzzle is, however, the mechanism underlying charge generation via relaxed interfacial charge-transfer (CT) excitons that also exhibit an internal quantum efficiency close to unity. Here, we provide evidence for efficient charge generation via CT state absorption over a temperature range of 50-300 K, despite an intrinsically strong Coulomb binding energy of about 400 meV that cannot be modified by fullerene aggregation. We explain our observation by entropy-driven charge separation, with a key contribution from energy disorder. The energy disorder reduces the charge generation barrier by substantially gaining the entropy as electron hole distance increases, resulting in efficient CT exciton dissociation. Our results underline an emerging consideration of energy disorder in thermodynamic stability of charge pairs and highlight the energy disorder as a dominant factor for generating charges via the CT state. A discussion for a trade-off in harvesting charges from relaxed CT excitons is also provided.
|
|
| 68. |
|
|
| 69. |
- Qian, Deping, et al.
(författare)
-
Design rules for minimizing voltage losses in high-efficiency organic solar cells
- 2018
-
Ingår i: Nature Materials. - : NATURE PUBLISHING GROUP. - 1476-1122 .- 1476-4660. ; 17:8, s. 703-
-
Tidskriftsartikel (refereegranskat)abstract
- The open-circuit voltage of organic solar cells is usually lower than the values achieved in inorganic or perovskite photovoltaic devices with comparable bandgaps. Energy losses during charge separation at the donor-acceptor interface and non-radiative recombination are among the main causes of such voltage losses. Here we combine spectroscopic and quantum-chemistry approaches to identify key rules for minimizing voltage losses: (1) a low energy offset between donor and acceptor molecular states and (2) high photoluminescence yield of the low-gap material in the blend. Following these rules, we present a range of existing and new donor-acceptor systems that combine efficient photocurrent generation with electroluminescence yield up to 0.03%, leading to non-radiative voltage losses as small as 0.21 V. This study provides a rationale to explain and further improve the performance of recently demonstrated high-open-circuit-voltage organic solar cells.
|
|
| 70. |
- Qian, D. P., et al.
(författare)
-
Modulating molecular aggregation by facile heteroatom substitution of diketopyrrolopyrrole based small molecules for efficient organic solar cells
- 2015
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 3:48, s. 24349-24357
-
Tidskriftsartikel (refereegranskat)abstract
- In conjugated polymers and small molecules of organic solar cells, aggregation induced by intermolecular interactions governs the performance of photovoltaics. However, little attention has been paid to the connection between molecular structure and aggregation within solar cells based on soluble small molecules. Here we demonstrate modulation of intermolecular aggregation of two synthesized molecules through heteroatom substitution to develop an understanding of the role of aggregation in conjugated molecules. Molecule 1 (M1) based on 2-ethylhexyloxy-benzene substituted benzo[1,2-b:4,5-b']dithiophene (BDTP) and diketopyrrolopyrrole (DPP) displays strong aggregation in commonly used organic solvents, which is reduced in molecule 2 (M2) by facile oxygen atom substitution on the BDTP unit confirmed by absorption spectroscopy and optical microscopy, while it successfully maintains molecular planarity and favorable charge transport characteristics. Solar cells based on M2 exhibit more than double the photocurrent of devices based on M1 and yield a power conversion efficiency of 5.5%. A systematic investigation of molecular conformation, optoelectronic properties, molecular packing and crystallinity as well as film morphology reveals structure dependent aggregation responsible for the performance difference between the two conjugated molecules.
|
|
