| 1. |
- Abdel Aziz, Ilaria, et al.
(författare)
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Drug delivery via a 3D electro-swellable conjugated polymer hydrogel
- 2024
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Ingår i: Journal of materials chemistry. B. - : ROYAL SOC CHEMISTRY. - 2050-750X .- 2050-7518.
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Tidskriftsartikel (refereegranskat)abstract
- Spatiotemporal controlled drug delivery minimizes side-effects and enables therapies that require specific dosing patterns. Conjugated polymers (CP) can be used for electrically controlled drug delivery; however so far, most demonstrations were limited to molecules up to 500 Da. Larger molecules could be incorporated only during the CP polymerization and thus limited to a single delivery. This work harnesses the record volume changes of a glycolated polythiophene p(g3T2) for controlled drug delivery. p(g3T2) undergoes reversible volumetric changes of up to 300% during electrochemical doping, forming pores in the nm-size range, resulting in a conducting hydrogel. p(g3T2)-coated 3D carbon sponges enable controlled loading and release of molecules spanning molecular weights of 800-6000 Da, from simple dyes up to the hormone insulin. Molecules are loaded as a combination of electrostatic interactions with the charged polymer backbone and physical entrapment in the porous matrix. Smaller molecules leak out of the polymer while larger ones could not be loaded effectively. Finally, this work shows the temporally patterned release of molecules with molecular weight of 1300 Da and multiple reloading and release cycles without affecting the on/off ratio.
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| 2. |
- Abdel Aziz, Ilaria, et al.
(författare)
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Electrochemical modulation of mechanical properties of glycolated polythiophenes
- 2024
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Ingår i: Materials Horizons. - : ROYAL SOC CHEMISTRY. - 2051-6347 .- 2051-6355.
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical doping of organic mixed ionic-electronic conductors is key for modulating their conductivity, charge storage and volume enabling high performing bioelectronic devices such as recording and stimulating electrodes, transistors-based sensors and actuators. However, electrochemical doping has not been explored to the same extent for modulating the mechanical properties of OMIECs on demand. Here, we report a qualitative and quantitative study on how the mechanical properties of a glycolated polythiophene, p(g3T2), change in situ during electrochemical doping and de-doping. The Young's modulus of p(g3T2) changes from 69 MPa in the dry state to less than 10 MPa in the hydrated state and then further decreases down to 0.4 MPa when electrochemically doped. With electrochemical doping-dedoping the Young's modulus of p(g3T2) changes by more than one order of magnitude reversibly, representing the largest modulation reported for an OMIEC. Furthermore, we show that the electrolyte concentration affects the magnitude of the change, demonstrating that in less concentrated electrolytes more water is driven into the film due to osmosis and therefore the film becomes softer. Finally, we find that the oligo ethylene glycol side chain functionality, specifically the length and asymmetry, affects the extent of modulation. Our findings show that glycolated polythiophenes are promising materials for mechanical actuators with a tunable modulus similar to the range of biological tissues, thus opening a pathway for new mechanostimulation devices. This work investigates the changes in the mechanical properties of glycolated polythiophenes induced by electrochemical addressing and by electrolyte concentration, due to its ability to stabilize water.
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| 3. |
- Alsufyani, Maryam, et al.
(författare)
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Lactone Backbone Density in Rigid Electron-Deficient Semiconducting Polymers Enabling High n-type Organic Thermoelectric Performance
- 2022
-
Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 61:7
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Tidskriftsartikel (refereegranskat)abstract
- Three lactone-based rigid semiconducting polymers were designed to overcome major limitations in the development of n-type organic thermoelectrics, namely electrical conductivity and air stability. Experimental and theoretical investigations demonstrated that increasing the lactone group density by increasing the benzene content from 0 % benzene (P-0), to 50 % (P-50), and 75 % (P-75) resulted in progressively larger electron affinities (up to 4.37 eV), suggesting a more favorable doping process, when employing (N-DMBI) as the dopant. Larger polaron delocalization was also evident, due to the more planarized conformation, which is proposed to lead to a lower hopping energy barrier. As a consequence, the electrical conductivity increased by three orders of magnitude, to achieve values of up to 12 S cm and Power factors of 13.2 mu Wm(-1) K-2 were thereby enabled. These findings present new insights into material design guidelines for the future development of air stable n-type organic thermoelectrics.
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| 4. |
- Alsufyani, Maryam, et al.
(författare)
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The effect of aromatic ring size in electron deficient semiconducting polymers for n-type organic thermoelectrics
- 2020
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 8:43, s. 15150-15157
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Tidskriftsartikel (refereegranskat)abstract
- N-type semiconducting polymers have been recently utilized in thermoelectric devices, however they have typically exhibited low electrical conductivities and poor device stability, in contrast to p-type semiconductors, which have been much higher performing. This is due in particular to the n-type semiconductors low doping efficiency, and poor charge carrier mobility. Strategies to enhance the thermoelectric performance of n-type materials include optimizing the electron affinity (EA) with respect to the dopant to improve the doping process and increasing the charge carrier mobility through enhanced molecular packing. Here, we report the design, synthesis and characterization of fused electron-deficient n-type copolymers incorporating the electron withdrawing lactone unit along the backbone. The polymers were synthesized using metal-free aldol condensation conditions to explore the effect of enlarging the central phenyl ring to a naphthalene ring, on the electrical conductivity. When n-doped with N-DMBI, electrical conductivities of up to 0.28 S cm(-1), Seebeck coefficients of -75 mu V K-1 and maximum Power factors of 0.16 mu W m(-1) K-2 were observed from the polymer with the largest electron affinity of -4.68 eV. Extending the aromatic ring reduced the electron affinity, due to reducing the density of electron withdrawing groups and subsequently the electrical conductivity reduced by almost two orders of magnitude.
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| 5. |
- Chen, Hu, et al.
(författare)
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Acene Ring Size Optimization in Fused Lactam Polymers Enabling High n-Type Organic Thermoelectric Performance
- 2021
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Ingår i: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 143:1, s. 260-268
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Tidskriftsartikel (refereegranskat)abstract
- Three n-type fused lactam semiconducting polymers were synthesized for thermoelectric and transistor applications via a cheap, highly atom-efficient, and nontoxic transition-metal free aldol polycondensation. Energy level analysis of the three polymers demonstrated that reducing the central acene core size from two anthracenes (A-A), to mixed naphthalene-anthracene (A-N), and two naphthalene cores (N-N) resulted in progressively larger electron affinities, thereby suggesting an increasingly more favorable and efficient solution doping process when employing 4-(2,3-dihydro-1,3-dimethyl-1H-benzimidazol-2-yl)-N,N-dimethylbenzenamine (N-DMBI) as the dopant. Meanwhile, organic field effect transistor (OFET) mobility data showed the N-N and A-N polymers to feature the highest charge carrier mobilities, further highlighting the benefits of aryl core contraction to the electronic performance of the materials. Ultimately, the combination of these two factors resulted in N-N, A-N, and A-A to display power factors (PFs) of 3.2 mu W m(-1) K-2, 1.6 mu W m(-1 )K(-2), and 0.3 mu W m(-1) K-2, respectively, when doped with N-DMBI, whereby the PFs recorded for N-N and A-N are among the highest reported in the literature for n-type polymers. Importantly, the results reported in this study highlight that modulating the size of the central acene ring is a highly effective molecular design strategy to optimize the thermoelectric performance of conjugated polymers, thus also providing new insights into the molecular design guidelines for the next generation of high-performance n-type materials for thermoelectric applications.
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| 6. |
- Clarke, Andrew J., et al.
(författare)
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Non-fullerene acceptor photostability and its impact on organic solar cell lifetime
- 2021
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Ingår i: Cell Reports Physical Science. - : Elsevier. - 2666-3864. ; 2:7
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Tidskriftsartikel (refereegranskat)abstract
- The development of non-fullerene acceptors (NFAs) has facilitated the realization of efficient organic solar cells (OSCs) with minimal burn-in losses and excellent long-term stability. However, the role of NFA molecular structures on device stability remains unclear, limiting commercialization of NFA-based OSCs. Herein, the photostability of 10 OSC devices, fabricated with various NFAs (O-IDTBR, EH-IDTBR, ITIC, and ITIC-M) blended with donor polymers (PTB7-Th, PffBT4T-2OD, and PBDB-T), is investigated. O-IDTBR and EH-IDTBR form highly stable devices with all three polymers, whereas ITIC and ITIC-M devices suffer from burn-in losses and long-term degradation. Conformational instability is found to be responsible for the poor photostability of ITIC and ITIC-M, resulting in poor device stability. Twisting and potential breakage of the chemical bond that links the end group to the main backbone of ITIC and ITIC-M molecules causes undesirable conformational changes. Potential strategies to overcome such detrimental photo-induced conformational changes in NFAs are proposed.
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| 7. |
- Craighero, Mariavittoria, 1995, et al.
(författare)
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Impact of Oligoether Side-Chain Length on the Thermoelectric Properties of a Polar Polythiophene
- 2024
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Ingår i: ACS Applied Electronic Materials. - : AMER CHEMICAL SOC. - 2637-6113. ; 6:5, s. 2909-2916
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Forskningsöversikt (refereegranskat)abstract
- Conjugated polymers with oligoether side chains make up a promising class of thermoelectric materials. In this work, the impact of the side-chain length on the thermoelectric and mechanical properties of polythiophenes is investigated. Polymers with tri-, tetra-, or hexaethylene glycol side chains are compared, and the shortest length is found to result in thin films with the highest degree of order upon doping with the p-dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ). As a result, a stiff material with an electrical conductivity of up to 830 +/- 15 S cm(-1) is obtained, resulting in a thermoelectric power factor of about 21 mu W m(-1) K-2 in the case of as-cast films. Aging at ambient conditions results in an initial decrease in thermoelectric properties but then yields a highly stable performance for at least 3 months, with values of about 200 S cm(-1) and 5 mu W m(-1) K-2. Evidently, identification of the optimal side-chain length is an important criterion for the design of conjugated polymers for organic thermoelectrics.
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| 8. |
- Gladisch, Johannes, et al.
(författare)
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An Electroactive Filter with Tunable Porosity Based on Glycolated Polythiophene
- 2022
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Ingår i: Small Science. - : Wiley. - 2688-4046. ; 2:4
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Tidskriftsartikel (refereegranskat)abstract
- The porosity of filters is typically fixed; thus, complex purification processes require application of multiple specialized filters. In contrast, smart filters with controllable and tunable properties enable dynamic separation in a single setup. Herein, an electroactive filter with controllable pore size is demonstrated. The electroactive filter is based on a metal mesh coated with a polythiophene polymer with ethylene glycol sidechains (p(g3T2)) that exhibit unprecedented voltage-driven volume changes. By optimizing the polymer coating on the mesh, controllable porosity during electrochemical addressing is achieved. The pores reversibly open and close, with a dynamic range of more than 95%, corresponding to over 30 mu m change of pores widths. Furthermore, the pores widths could be defined by applied potential with a 10 mu m resolution. From among hundreds of pores from different samples, about 90% of the pores could be closed completely, while only less than 1% are inactive. Finally, the electroactive filter is used to control the flow of a dye, highlighting the potential for flow control and smart filtration applications.
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| 9. |
- Gladisch, Johannes, et al.
(författare)
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Reversible Electronic Solid-Gel Switching of a Conjugated Polymer
- 2020
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Ingår i: ADVANCED SCIENCE. - : WILEY. - 2198-3844. ; 7:2
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Tidskriftsartikel (refereegranskat)abstract
- Conjugated polymers exhibit electrically driven volume changes when included in electrochemical devices via the exchange of ions and solvent. So far, this volumetric change is limited to 40% and 100% for reversible and irreversible systems, respectively, thus restricting potential applications of this technology. A conjugated polymer that reversibly expands by about 300% upon addressing, relative to its previous contracted state, while the first irreversible actuation can achieve values ranging from 1000-10 000%, depending on the voltage applied is reported. From experimental and theoretical studies, it is found that this large and reversible volumetric switching is due to reorganization of the polymer during swelling as it transforms between a solid-state phase and a gel, while maintaining percolation for conductivity. The polymer is utilized as an electroactive cladding to reduce the void sizes of a porous carbon filter electrode by 85%.
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| 10. |
- Hallam, Toby, et al.
(författare)
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Local Charge Trapping in Conjugated Polymers Resolved by Scanning Kelvin Probe Microscopy
- 2009
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 103:25
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure of conjugated polymers is heterogeneous on the length scale of individual polymer chains, but little is known about how this affects their electronic properties. Here we use scanning Kelvin probe microscopy with resolution-enhancing carbon nanotube tips to study charge transport on a 100 nm scale in a chain-extended, semicrystalline conjugated polymer. We show that the disordered grain boundaries between crystalline domains constitute preferential charge trapping sites and lead to variations on a 100 nm scale of the carrier concentration under accumulation conditions.
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| 11. |
- Kiefer, David, 1989, et al.
(författare)
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Double doping of conjugated polymers with monomer molecular dopants
- 2019
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 18:2, s. 149-155
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Tidskriftsartikel (refereegranskat)abstract
- Molecular doping is a crucial tool for controlling the charge-carrier concentration in organic semiconductors. Each dopant molecule is commonly thought to give rise to only one polaron, leading to a maximum of one donor:acceptor charge-transfer complex and hence an ionization efficiency of 100%. However, this theoretical limit is rarely achieved because of incomplete charge transfer and the presence of unreacted dopant. Here, we establish that common p-dopants can in fact accept two electrons per molecule from conjugated polymers with a low ionization energy. Each dopant molecule participates in two charge-transfer events, leading to the formation of dopant dianions and an ionization efficiency of up to 200%. Furthermore, we show that the resulting integer charge-transfer complex can dissociate with an efficiency of up to 170%. The concept of double doping introduced here may allow the dopant fraction required to optimize charge conduction to be halved.
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| 12. |
- Kiefer, David, 1989, et al.
(författare)
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Enhanced n-Doping Efficiency of a Naphthalenediimide-Based Copolymer through Polar Side Chains for Organic Thermoelectrics
- 2018
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Ingår i: ACS Energy Letters. - : American Chemical Society (ACS). - 2380-8195. ; 3:2, s. 278-285
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Tidskriftsartikel (refereegranskat)abstract
- N-doping of conjugated polymers either requires a high dopant fraction or yields a low electrical conductivity because of their poor compatibility with molecular dopants. We explore n-doping of the polar naphthalenediimide–bithiophene copolymer p(gNDI-gT2) that carries oligoethylene glycol-based side chains and show that the polymer displays superior miscibility with the benzimidazole–dimethylbenzenamine-based n-dopant N-DMBI. The good compatibility of p(gNDI-gT2) and N-DMBI results in a relatively high doping efficiency of 13% for n-dopants, which leads to a high electrical conductivity of more than 10–1 S cm–1 for a dopant concentration of only 10 mol % when measured in an inert atmosphere. We find that the doped polymer is able to maintain its electrical conductivity for about 20 min when exposed to air and recovers rapidly when returned to a nitrogen atmosphere. Overall, solution coprocessing of p(gNDI-gT2) and N-DMBI results in a larger thermoelectric power factor of up to 0.4 μW K–2 m–1 compared to other NDI-based polymers.
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| 13. |
- LeCroy, Garrett, et al.
(författare)
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Role of aggregates and microstructure of mixed-ionic-electronic-conductors on charge transport in electrochemical transistors
- 2023
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Ingår i: Materials Horizons. - 2051-6355 .- 2051-6347. ; 10:7, s. 2568-2578
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Tidskriftsartikel (refereegranskat)abstract
- Synthetic efforts have delivered a library of organic mixed ionic-electronic conductors (OMIECs) with high performance in electrochemical transistors. The most promising materials are redox-active conjugated polymers with hydrophilic side chains that reach high transconductances in aqueous electrolytes due to volumetric electrochemical charging. Current approaches to improve transconductance and device stability focus mostly on materials chemistry including backbone and side chain design. However, other parameters such as the initial microstructure and microstructural rearrangements during electrochemical charging are equally important and are influenced by backbone and side chain chemistry. In this study, we employ a polymer system to investigate the fundamental electrochemical charging mechanisms of OMIECs. We couple in situ electronic charge transport measurements and spectroelectrochemistry with ex situ X-ray scattering electrochemical charging experiments and find that polymer chains planarize during electrochemical charging. Our work shows that the most effective conductivity modulation is related to electrochemical accessibility of well-ordered, interconnected aggregates that host high mobility electronic charge carriers. Electrochemical stress cycling induces microstructural changes, but we find that these aggregates can largely maintain order, providing insights on the structural stability and reversibility of electrochemical charging in these systems. This work shows the importance of material design for creating OMIECs that undergo structural rearrangements to accommodate ions and electronic charge carriers during which percolating networks are formed for efficient electronic charge transport.
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| 14. |
- Lin, Yuanbao, et al.
(författare)
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18.73% efficient and stable inverted organic photovoltaics featuring a hybrid hole-extraction layer
- 2023
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Ingår i: Materials Horizons. - : Royal Society of Chemistry (RSC). - 2051-6355 .- 2051-6347. ; 10:4, s. 1292-1300
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Tidskriftsartikel (refereegranskat)abstract
- Developing efficient and stable organic photovoltaics (OPVs) is crucial for the technology's commercial success. However, combining these key attributes remains challenging. Herein, we incorporate the small molecule 2-((3,6-dibromo-9H-carbazol-9-yl)ethyl)phosphonic acid (Br-2PACz) between the bulk-heterojunction (BHJ) and a 7 nm-thin layer of MoO3 in inverted OPVs, and study its effects on the cell performance. We find that the Br-2PACz/MoO3 hole-extraction layer (HEL) boosts the cell's power conversion efficiency (PCE) from 17.36% to 18.73% (uncertified), making them the most efficient inverted OPVs to date. The factors responsible for this improvement include enhanced charge transport, reduced carrier recombination, and favourable vertical phase separation of donor and acceptor components in the BHJ. The Br-2PACz/MoO3-based OPVs exhibit higher operational stability under continuous illumination and thermal annealing (80 degrees C). The T-80 lifetime of OPVs featuring Br-2PACz/MoO3 - taken as the time over which the cell's PCE reduces to 80% of its initial value - increases compared to MoO3-only cells from 297 to 615 h upon illumination and from 731 to 1064 h upon continuous heating. Elemental analysis of the BHJs reveals the enhanced stability to originate from the partially suppressed diffusion of Mo ions into the BHJ and the favourable distribution of the donor and acceptor components induced by the Br-2PACz.
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| 15. |
- Lin, Yuanbao, et al.
(författare)
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18.9% Efficient Organic Solar Cells Based on n-Doped Bulk-Heterojunction and Halogen-Substituted Self-Assembled Monolayers as Hole Extracting Interlayers
- 2022
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6840 .- 1614-6832. ; 12:45
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Tidskriftsartikel (refereegranskat)abstract
- The influence of halogen substitutions (F, Cl, Br, and I) on the energy levels of the self-assembled hole-extracting molecule [2-(9H-Carbazol-9-yl)ethyl]phosphonic acid (2PACz), is investigated. It is found that the formation of self-assembled monolayers (SAMs) of [2-(3,6-Difluoro-9H-carbazol-9-yl)ethyl]phosphonic acid (F-2PACz), [2-(3,6-Dichloro-9H-carbazol-9-yl)ethyl]phosphonic acid (Cl-2PACz), [2-(3,6-Dibromo-9H-carbazol-9-yl)ethyl]phosphonic acid (Br-2PACz), and [2-(3,6-Diiodo-9H-carbazol-9-yl)ethyl]phosphonic acid (I-2PACz) directly on indium tin oxide (ITO) increases its work function from 4.73 eV to 5.68, 5.77, 5.82, and 5.73 eV, respectively. Combining these ITO/SAM electrodes with the ternary bulk-heterojunction (BHJ) system PM6:PM7-Si:BTP-eC9 yields organic photovoltaic (OPV) cells with power conversion efficiency (PCE) in the range of 17.7%-18.5%. OPVs featuring Cl-2PACz SAMs yield the highest PCE of 18.5%, compared to cells with F-2PACz (17.7%), Br-2PACz (18.0%), or I-2PACz (18.2%). Data analysis reveals that the enhanced performance of Cl-2PACz-based OPVs relates to the increased hole mobility, decreased interface resistance, reduced carrier recombination, and longer carrier lifetime. Furthermore, OPVs featuring Cl-2PACz show enhanced stability under continuous illumination compared to ITO/PEDOT:PSS-based cells. Remarkably, the introduction of the n-dopant benzyl viologen into the BHJ further boosted the PCE of the ITO/Cl-2PACz cells to a maximum value of 18.9%, a record-breaking value for SAM-based OPVs and on par with the best-performing OPVs reported to date.
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| 16. |
- Liu, Tiefeng, et al.
(författare)
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Ground-state electron transfer in all-polymer donor:acceptor blends enables aqueous processing of water-insoluble conjugated polymers
- 2023
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Ingår i: Nature Communications. - : NATURE PORTFOLIO. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Water-based conductive inks are vital for the sustainable manufacturing and widespread adoption of organic electronic devices. Traditional methods to produce waterborne conductive polymers involve modifying their backbone with hydrophilic side chains or using surfactants to form and stabilize aqueous nanoparticle dispersions. However, these chemical approaches are not always feasible and can lead to poor material/device performance. Here, we demonstrate that ground-state electron transfer (GSET) between donor and acceptor polymers allows the processing of water-insoluble polymers from water. This approach enables macromolecular charge-transfer salts with 10,000x higher electrical conductivities than pristine polymers, low work function, and excellent thermal/solvent stability. These waterborne conductive films have technological implications for realizing high-performance organic solar cells, with efficiency and stability superior to conventional metal oxide electron transport layers, and organic electrochemical neurons with biorealistic firing frequency. Our findings demonstrate that GSET offers a promising avenue to develop water-based conductive inks for various applications in organic electronics. Chemical approaches to improve aqueous dispersions of conjugated polymers are limited by the feasibility of modifying the backbone or lead to poor performance. Here, Liu et al. show that ground-state electron transfer in donor:acceptor blends aids aqueous dispersion, for high conductivity and solubility.
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| 17. |
- Marks, Adam, et al.
(författare)
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Synthetic Nuances to Maximize n-Type Organic Electrochemical Transistor and Thermoelectric Performance in Fused Lactam Polymers
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:10, s. 4642-4656
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Tidskriftsartikel (refereegranskat)abstract
- A series of fully fused n-type mixed conduction lactam polymers p(g(7)NC(n)N), systematically increasing the alkyl side chain content, are synthesized via an inexpensive, nontoxic, precious-metal-free aldol polycondensation. Employing these polymers as channel materials in organic electrochemical transistors (OECTs) affords state-of-the-art n-type performance with p(g(7)NC(10)N) recording an OECT electron mobility of 1.20 x 10(-2) cm(2) V-1 s(-1) and a mu C* figure of merit of 1.83 F cm(-1) V-1 s(-1). In parallel to high OECT performance, upon solution doping with (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine (N-DMBI), the highest thermoelectric performance is observed for p(g(7)NC(4)N), with a maximum electrical conductivity of 7.67 S cm(-1) and a power factor of 10.4 mu Wm(-1) K-2. These results are among the highest reported for n-type polymers. Importantly, while this series of fused polylactam organic mixed ionic-electronic conductors (OMIECs) highlights that synthetic molecular design strategies to bolster OECT performance can be translated to also achieve high organic thermoelectric (OTE) performance, a nuanced synthetic approach must be used to optimize performance. Herein, we outline the performance metrics and provide new insights into the molecular design guidelines for the next generation of high-performance n-type materials for mixed conduction applications, presenting for the first time the results of a single polymer series within both OECT and OTE applications.
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| 18. |
- Mathijssen, Simon G. J., et al.
(författare)
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Revealing Buried Interfaces to Understand the Origins of Threshold Voltage Shifts in Organic Field-Effect Transistors
- 2010
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Ingår i: Advanced Materials. - : Wiley-VCH Verlag. - 0935-9648 .- 1521-4095. ; 22:45, s. 5105-
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Tidskriftsartikel (refereegranskat)abstract
- The semiconductor of an organic field-effect transistor is stripped with adhesive tape, yielding an exposed gate dielectric, accessible for various characterization techniques. By using scanning Kelvin probe microscopy we reveal that trapped charges after gate bias stress are located at the gate dielectric and not in the semiconductor. Charging of the gate dielectric is confirmed by the fact that the threshold voltage shift remains, when a pristine organic semiconductor is deposited on the exposed gate dielectric of a stressed and delaminated field-effect transistor.
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| 19. |
- Moser, Maximilian, et al.
(författare)
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Controlling Electrochemically Induced Volume Changes in Conjugated Polymers by Chemical Design : from Theory to Devices
- 2021
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; n/a:n/a
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemically induced volume changes in organic mixed ionic-electronic conductors (OMIECs) are particularly important for their use in dynamic microfiltration systems, biomedical machinery, and electronic devices. Although significant advances have been made to maximize the dimensional changes that can be accomplished by OMIECs, there is currently limited understanding of how changes in their molecular structures impact their underpinning fundamental processes and their performance in electronic devices. Herein, a series of ethylene glycol functionalized conjugated polymers is synthesized, and their electromechanical properties are evaluated through a combined approach of experimental measurements and molecular dynamics simulations. As demonstrated, alterations in the molecular structure of OMIECs impact numerous processes occurring during their electrochemical swelling, with sidechain length shortening decreasing the number of incorporated water molecules, reducing the generated void volumes and promoting the OMIECs to undergo different phase transitions. Ultimately, the impact of these combined molecular processes is assessed in organic electrochemical transistors, revealing that careful balancing of these phenomena is required to maximize device performance.
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| 20. |
- Moser, Maximilian, et al.
(författare)
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Side Chain Redistribution as a Strategy to Boost Organic Electrochemical Transistor Performance and Stability
- 2020
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- A series of glycolated polythiophenes for use in organic electrochemical transistors (OECTs) is designed and synthesized, differing in the distribution of their ethylene glycol chains that are tethered to the conjugated backbone. While side chain redistribution does not have a significant impact on the optoelectronic properties of the polymers, this molecular engineering strategy strongly impacts the water uptake achieved in the polymers. By careful optimization of the water uptake in the polymer films, OECTs with unprecedented steady-state performances in terms of [mu C*] and current retentions up to 98% over 700 electrochemical switching cycles are developed.
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| 21. |
- Nguyen, Malgorzata, et al.
(författare)
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Improving OFF‐State Bias‐Stress Stability in High‐Mobility Conjugated Polymer Transistors with an Anti‐Solvent Treatment
- 2023
-
Ingår i: Advanced Materials. - : John Wiley & Sons. - 0935-9648 .- 1521-4095. ; 35:16
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Tidskriftsartikel (refereegranskat)abstract
- Conjugated polymer field-effect transistors are emerging as an enabling technology for flexible electronics due to their excellent mechanical properties combined with sufficiently high charge carrier mobilities and compatibility with large-area, low-temperature processing. However, their electrical stability remains a concern. ON-state (accumulation mode) bias-stress instabilities in organic semiconductors have been widely studied, and multiple mitigation strategies have been suggested. In contrast, OFF-state (depletion mode) bias-stress instabilities remain poorly understood despite being crucial for many applications in which the transistors are held in their OFF-state for most of the time. Here, we present a simple method of using an anti-solvent treatment to achieve significant improvements in OFF-state bias-stress and environmental stability as well as general device performance for one of the best performing polymers, solution-processable indacenodithiophene-co-benzothiadiazole (IDT-BT). IDT-BT is weakly crystalline, and we attribute the notable improvements to an anti-solvent-induced, increased degree of crystallinity, resulting in a lower probability of electron trapping and the removal of charge traps. Our work highlights the importance of the microstructure in weakly crystalline polymer films and offers a simple processing strategy for achieving the reliability required for applications in flexible electronics.
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| 22. |
- Quill, Tyler J., et al.
(författare)
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Charge Carrier Induced Structural Ordering And Disordering in Organic Mixed Ionic Electronic Conductors
- 2024
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Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 36:15
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Tidskriftsartikel (refereegranskat)abstract
- Operational stability underpins the successful application of organic mixed ionic-electronic conductors (OMIECs) in a wide range of fields, including biosensing, neuromorphic computing, and wearable electronics. In this work, both the operation and stability of a p-type OMIEC material of various molecular weights are investigated. Electrochemical transistor measurements reveal that device operation is very stable for at least 300 charging/discharging cycles independent of molecular weight, provided the charge density is kept below the threshold where strong charge–charge interactions become likely. When electrochemically charged to higher charge densities, an increase in device hysteresis and a decrease in conductivity due to a drop in the hole mobility arising from long-range microstructural disruptions are observed. By employing operando X-ray scattering techniques, two regimes of polaron-induced structural changes are found: 1) polaron-induced structural ordering at low carrier densities, and 2) irreversible structural disordering that disrupts charge transport at high carrier densities, where charge–charge interactions are significant. These operando measurements also reveal that the transfer curve hysteresis at high carrier densities is accompanied by an analogous structural hysteresis, providing a microstructural basis for such instabilities. This work provides a mechanistic understanding of the structural dynamics and material instabilities of OMIEC materials during device operation.
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| 23. |
- Siemons, Nicholas, et al.
(författare)
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Controlling swelling in mixed transport polymers through alkyl side-chain physical cross-linking
- 2023
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 120:35
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Tidskriftsartikel (refereegranskat)abstract
- Semiconducting conjugated polymers bearing glycol side chains can simultaneously transport both electronic and ionic charges with high charge mobilities, making them ideal electrode materials for a range of bioelectronic devices. However, heavily glycolated conjugated polymer films have been observed to swell irreversibly when subjected to an electrochemical bias in an aqueous electrolyte. The excessive swelling can lead to the degradation of their microstructure, and subsequently reduced device performance. An effective strategy to control polymer film swelling is to copolymerize glycolated repeat units with a fraction of monomers bearing alkyl side chains, although the microscopic mechanism that constrains swelling is unknown. Here we investigate, experimentally and computationally, a series of archetypal mixed transporting copolymers with varying ratios of glycolated and alkylated repeat units. Experimentally we observe that exchanging 10% of the glycol side chains for alkyl leads to significantly reduced film swelling and an increase in electrochemical stability. Through molecular dynamics simulation of the amorphous phase of the materials, we observe the formation of polymer networks mediated by alkyl side-chain interactions. When in the presence of water, the network becomes increasingly connected, counteracting the volumetric expansion of the polymer film.
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| 24. |
- Simatos, Dimitrios, et al.
(författare)
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Effects of Processing-Induced Contamination on Organic Electronic Devices
- 2023
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Ingår i: Small Methods. - : Wiley. - 2366-9608. ; 7:11
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Tidskriftsartikel (refereegranskat)abstract
- Organic semiconductors are a family of pi-conjugated compounds used in many applications, such as displays, bioelectronics, and thermoelectrics. However, their susceptibility to processing-induced contamination is not well understood. Here, it is shown that many organic electronic devices reported so far may have been unintentionally contaminated, thus affecting their performance, water uptake, and thin film properties. Nuclear magnetic resonance spectroscopy is used to detect and quantify contaminants originating from the glovebox atmosphere and common laboratory consumables used during device fabrication. Importantly, this in-depth understanding of the sources of contamination allows the establishment of clean fabrication protocols, and the fabrication of organic field effect transistors (OFETs) with improved performance and stability. This study highlights the role of unintentional contaminants in organic electronic devices, and demonstrates that certain stringent processing conditions need to be met to avoid scientific misinterpretation, ensure device reproducibility, and facilitate performance stability. The experimental procedures and conditions used herein are typical of those used by many groups in the field of solution-processed organic semiconductors. Therefore, the insights gained into the effects of contamination are likely to be broadly applicable to studies, not just of OFETs, but also of other devices based on these materials.
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| 25. |
- Wang, Yazhou, et al.
(författare)
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Hybrid Alkyl-Ethylene Glycol Side Chains Enhance Substrate Adhesion and Operational Stability in Accumulation Mode Organic Electrochemical Transistors
- 2019
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Ingår i: Chemistry of Materials. - : AMER CHEMICAL SOC. - 0897-4756 .- 1520-5002. ; 31:23, s. 9797-9806
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Tidskriftsartikel (refereegranskat)abstract
- Donor-acceptor copolymers featuring electron-deficient isoindigo units and electron-rich 3,4-ethyl-E enedioxy (EDOT) groups are presented as new materials for accumulation mode organic electrochemical transistors (OECTs). Grafting hybrid alkyl-ethylene glycol side chains on the isoindigo units of the copolymer leads to OECTs with outstanding substrate adhesion and operational stability in contact with an aqueous electrolyte, as demonstrated by their preserved performance after extensive ultrasonication (1.5 h) or after continuous on-off switching for over 6 h. Hybrid side chains outperform copolymers with alkyl only or ethylene glycol only side chains, which retain only 27% and 10% of the on currents after 40 min of on-off switching, respectively, under the same biasing conditions. These devices are promising candidates for in vitro and in vivo bioelectronics, applications where stability as well as robust adhesion of the conjugated polymer to the substrate are essential.
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| 26. |
- Wang, Yazhou, et al.
(författare)
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n-Type Organic Electrochemical Transistors with High Transconductance and Stability
- 2023
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 35:2, s. 405-415
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Tidskriftsartikel (refereegranskat)abstract
- An n-type conjugated polymer based on diazaisoindigo (AIID) and fluorinated thiophene units is introduced. Combining the strong electron-accepting properties of AIID with backbone fluorination produced gAIID-2FT, leading to organic electrochemical transistors (OECTs) with normalized values of 4.09 F cm-1 V-1 s-1 and a normalized transconductance (gm,norm) of 0.94 S cm-1. The resulting OECTs exhibit exceptional operational stability and long shelf-life in ambient conditions, preserving 100% of the original maximum drain current after over 3 h of continuous operation and 28 days of storage in the air. Our work highlights the advantages of integrating strong electron acceptors with donor fluorination to boost the performance and stability of n-type OECTs.
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