Operational electrochemical stability of thiophene-thiazole copolymers probed by resonant Raman spectroscopy

Wade, Jessica; Wood, Sebastian; Beatrup, Daniel; Hurhangee, Michael; Bronstein, Hugo; McCulloch, Iain; Durrant, James R.; Kim, Jinhyun

doi:10.1063/1.4923197

Cited by 16 publications

(14 citation statements)

References 38 publications

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“…In order to inject holes in to the material and control the charge density, we use chronoamperometry to apply a square wave potential and simultaneously measure the temporal current response. Characterization techniques, such as UV−vis and resonant Raman spectroscopy, can be performed in situ and provide information about changes to the optical and structural properties of the oxidized material …”

Section: Methodsmentioning

confidence: 99%

“…Polarons can be formed by charge injection, chemical doping, or electrochemical doping, as well as by charge generation via photoexcitation. − Regardless of how they are formed, polarons in P3HT are similar in nature and exhibit similar spectroscopic signatures. , Photoexcitation can lead to the formation of other types of charge carriers, such as polaron pairs, whose spectral signatures are difficult to distinguish from those of polarons. , Compared to photogeneration and chemical doping, electrochemical doping of P3HT allows precise control of polaron formation in terms of its density . Here, a P3HT film is deposited on conductive glass and immersed in an inert electrolyte, and the polaron density is controlled via an electrochemical potential to the film in a three-electrode cell configuration, while Raman spectroscopic measurements are performed simultaneously (see Figure S1 for experimental setup) under resonant excitation conditions in order to perform in situ electrochemical resonant Raman spectroscopy (ERRS).…”

Section: Introductionmentioning

confidence: 99%

“…20,21 Compared to photogeneration and chemical doping, electrochemical doping of P3HT allows precise control of polaron formation in terms of its density. 22 Here, a P3HT film is deposited on conductive glass and immersed in an inert electrolyte, and the polaron density is controlled via an electrochemical potential to the film in a three-electrode cell configuration, while Raman spectroscopic measurements are performed simultaneously (see Figure S1 for experimental setup) under resonant excitation conditions in order to perform in situ electrochemical resonant Raman spectroscopy (ERRS).…”

Section: ■ Introductionmentioning

confidence: 99%

“…Characterization techniques, such as UV−vis and resonant Raman spectroscopy, can be performed in situ and provide information about changes to the optical and structural properties of the oxidized material. 22 Film Preparation. Polymer and polymer/fullerene blends were dissolved in chlorobenzene at a concentration of 20 mg/ mL and left stirring at 80 °C overnight.…”

Section: ■ Introductionmentioning

confidence: 99%

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Impact of Molecular Order on Polaron Formation in Conjugated Polymers

et al. 2018

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The nature of polaron formation has profound implications on the transport of charge carriers in conjugated polymers, but still remains poorly understood. Here, we develop in situ electrochemical resonant Raman spectroscopy, a powerful structural probe that allows direct observation of polaron formation. We report that polaron formation in ordered poly(3-hexyl)thiophene (P3HT) polymer domains (crystalline phase) results in less pronounced changes in molecular conformation, indicating smaller lattice relaxation, compared to polarons generated in disordered polymer domains (amorphous phase) for which we observe large molecular conformational changes. These conformational changes are directly related to the effective conjugation length of the polymer. Furthermore, we elucidate how blending the P3HT polymer with phenyl C-61 butyric acid methyl ester affects polaron formation in the polymer. We find that blending disturbs polymer crystallinity, reducing the density of polarons that can form upon charge injection at the same potential, while the lost capacity is partly restored during postdeposition thermal annealing. Our study provides direct spectroscopic evidence for a lower degree of lattice reorganization in crystalline (and therefore more planar) polymers than in conformationally disordered polymers. This observation is consistent with higher charge carrier mobility and better device performance commonly found in crystalline polymer materials.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Impact of Molecular Order on Polaron Formation in Conjugated Polymers

et al. 2018

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“…Such behavior has been mainly ascribed to the uncompensated charged trapped in deep localized states in the semiconductor also caused by spurious electrochemical processes (Sirringhaus, 2005; Beatrup et al, 2014; Porrazzo et al, 2014). For example, the presence of polaronic states can cause an increased susceptibility to the electrochemical degradation (Wade et al, 2015). In fact, the presence of hole polarons under device operation is found to make polaron degradation pathways accessible (Beatrup et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

A Study on the Stability of Water-Gated Organic Field-Effect-Transistors Based on a Commercial p-Type Polymer

et al. 2019

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Robust electrolyte-gated organic field-effect-transistors (OFETs) are particularly needed for the development of biosensing devices. However, when a FET biosensor operates in aqueous environments or even in real biological fluids, some critical issues may arise due to the possible lack of environmental long-term and/or operational stability. An important source of instability is associated with the degradation of the organic electronic channel materials such as for instance, poly-3-hexylthiophene (P3HT), a benchmark commercially available p-type organic semiconductor. In this work, the investigation of critical parameters, such as the control over spurious electrochemical phenomena as well as the operating conditions that can affect water-gated OFETs lifetime, is reported, together with a proposed modeling of the P3HT stability curve over 1 week in water. The investigation of possible morphological/chemical modifications occurring at the polymer surface after operating in water for 2 weeks was carried out. Moreover, it is proven how the addition of a gel layer can extend the P3HT based water-gated OFET shelf life up to 2 months.

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