Raman spectroscopy and microscopy of electrochemically and chemically doped high-mobility semiconducting polymers

Francis, Colin G.; Fazzi, Daniele; Grimm, Stefan; Paulus, Fabian; Beck, Sebastian; Hillebrandt, Sabina; Pucci, Annemarie; Zaumseil, Jana

doi:10.1039/c7tc01277b

Cited by 65 publications

(73 citation statements)

References 55 publications

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“…It is known that different amounts of polymer dopes graphene differently to change its Raman peak positions 22,23 . The Raman G-peak position (scale: 1,570 to 1585 cm −1 ) is maintained at different depths in the printed graphene/PLA structure, (even at 80 m deep) (Fig.…”

Section: Resultsmentioning

confidence: 99%

3D-printed graphene/polymer structures for electron-tunneling based devices

Fernandes

Lynch

Berry

2020

Sci Rep

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Designing 3D printed micro-architectures using electronic materials with well-understood electronic transport within such structures will potentially lead to accessible device fabrication for 'on-demand' applications. Here we show controlled nozzle-extrusion based 3D printing of a commercially available nano-composite of graphene/polylactic acid, enabling the fabrication of a tensile gauge functioning via the readjustment of the electron-tunneling barrier width between conductive graphene-centers. The electronic transport in the graphene/polymer 3D printed structure exhibited the Fowler Nordheim mechanism with a tunneling width of 0.79-0.95 nm and graphene centers having a carrier concentration of 2.66 × 10 12 /cm 2. Furthermore, a mechanical strain that increases the electrontunneling width between graphene nanostructures (~ 38 nm) by only 0.19 Ǻ reduces the electron flux by 1e/s/nm 2 (from 18.51 to 19.51 e/s/nm 2) through the polylactic acid junctions in the 3D-printed heterostructure. This corresponds to a sensitivity of 2.59 Ω/Ω%, which compares well with other tensile gauges. We envision that the proposed electron-tunneling model for conductive 3D-printed structures with thermal expansion and external strain will lead to an evolution in the design of nextgeneration of 'on-demand' printed electronic and electromechanical devices.

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Section: Resultsmentioning

confidence: 99%

3D-printed graphene/polymer structures for electron-tunneling based devices

Fernandes

Lynch

Berry

2020

Sci Rep

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“…[ 18 ] As shown in Figure 2c, the ground state absorption peak of p(gPyDPP‐MeOT2) decreases upon oxidation of the copolymer while a new absorption peak appears for the hole polaron with a similar absorption spectrum as was previously reported for oxidized DPP copolymer analogs. [ 31,32 ] Electrochemically reversible polaron formation up to 0.7 V versus Ag/AgCl is observed for p(gPyDPP‐MeOT2). Applying higher potentials reveals bipolaron formation, corresponding to the charging of the polymer repeat units with two electrical charges, detected by a shift of the isosbestic point observed for the polaron formation as well as an increase of the absorption peak at low energy (>850 nm) (Figure S14d, Supporting Information).…”

Section: Figurementioning

confidence: 99%

Energetic Control of Redox‐Active Polymers toward Safe Organic Bioelectronic Materials

et al. 2020

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Organic semiconductors with polar sidechains have been identified as a promising class of materials for the field of bioelectronics. These materials, also called organic mixed ionic/electronic conductors (OMIECs), can exchange ions with aqueous electrolytes when electronic charge carriers are injected, transported, and stored in the bulk of the material. [1] Recent developments of OMIECs based on redox-active conjugated polymers [2][3][4][5][6][7][8] and novel device concepts [9,10] have opened up new pathways for bioelectronic devices including integrated circuits for electroencephalogram (EEG) monitoring [9] or low-power voltage amplifiers based on organic electrochemical transistors (OECTs). [11] Specifically, the OECT has drawn significant attention in the field of organic bioelectronics. It operates by electrochemically modulating the conductivity of a redox-active channel material with an electrolyte that is often aqueous, Avoiding faradaic side reactions during the operation of electrochemical devices is important to enhance the device stability, to achieve low power consumption, and to prevent the formation of reactive side-products. This is particularly important for bioelectronic devices, which are designed to operate in biological systems. While redox-active materials based on conducting and semiconducting polymers represent an exciting class of materials for bioelectronic devices, they are susceptible to electrochemical side-reactions with molecular oxygen during device operation. Here, electrochemical side reactions with molecular oxygen are shown to occur during organic electrochemical transistor (OECT) operation using high-performance, state-of-the-art OECT materials. Depending on the choice of the active material, such reactions yield hydrogen peroxide (H 2 O 2 ), a reactive side-product, which may be harmful to the local biological environment and may also accelerate device degradation. A design strategy is reported for the development of redox-active organic semiconductors based on donor-acceptor copolymers that prevents the formation of H 2 O 2 during device operation. This study elucidates the previously overlooked side-reactions between redox-active conjugated polymers and molecular oxygen in electrochemical devices for bioelectronics, which is critical for the operation of electrolyte-gated devices in application-relevant environments.

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“…From structural relaxations and polaron spin density analysis, the polaron localizes over three repeat units on the single chain, regardless the oligomer conformation. 53,54,55 By considering the most stable charged dimers, H-and J-dimer result in different spin delocalization. In the H-dimer, the spin is localized on a single chain featuring a prevalent intramolecular character, whereas in the J-dimer the polaron spin density is inter-molecularly delocalized, as reported in Figure 9a.…”

Section: Dft Calculations For Oligomers and Aggregates The Torsionalmentioning

confidence: 99%

Microstructural control suppresses thermal activation of electron transport at room temperature in polymer transistors

et al. 2019

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Recent demonstrations of inverted thermal activation of charge mobility in polymer field-effect transistors have excited the interest in transport regimes not limited by thermal barriers. However, rationalization of the limiting factors to access such regimes is still lacking. An improved understanding in this area is critical for development of new materials, establishing processing guidelines, and broadening of the range of applications. Here we show that precise processing of a diketopyrrolopyrrole-tetrafluorobenzene-based electron transporting copolymer results in single crystal-like and voltage-independent mobility with vanishing activation energy above 280 K. Key factors are uniaxial chain alignment and thermal annealing at temperatures within the melting endotherm of films. Experimental and computational evidences converge toward a picture of electrons being delocalized within crystalline domains of increased size. Residual energy barriers introduced by disordered regions are bypassed in the direction of molecular alignment by a more efficient interconnection of the ordered domains following the annealing process.

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Raman spectroscopy and microscopy of electrochemically and chemically doped high-mobility semiconducting polymers

Abstract: Raman spectra and DFT calculations show that p-doping of two semiconducting polymers affects mostly their electron-rich thienothiophene units.

Cited by 65 publications

References 55 publications

3D-printed graphene/polymer structures for electron-tunneling based devices

3D-printed graphene/polymer structures for electron-tunneling based devices

Energetic Control of Redox‐Active Polymers toward Safe Organic Bioelectronic Materials

Microstructural control suppresses thermal activation of electron transport at room temperature in polymer transistors

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