We study the effects of different electrolyte anions on the mixed ionic/electronic transport properties of organic electrochemical transistors (OECTs) based on poly(3-hexylthiophene-2,5diyl). We show that the transport properties depend on the anion present in the electrolyte, with greater source-drain currents resulting from the use of molecular anions such as hexafluorophosphate and trifluoromethanesulfonylimide than from the use of smaller atomic anions such as fluoride or chloride. Using spectroelectrochemistry, we show the maximum doping level that can be achieved in an aqueous environment is also anion-dependent. Furthermore, we find that the average electronic carrier mobility at a given doping level depends on the chemistry of the compensating counterion. We further investigate this dependence by electrochemical quartz crystal microbalance measurements, showing the solvation of the dopant anions within the polymer is drastically different depending on the choice of the anion. Surprisingly, we find that the kinetics of the doping process in these OECTs is faster for bulkier anions. Finally, we use electrochemical strain microscopy to resolve ion-dependent differences in doping and local swelling at the nanoscale, providing further insight into the coupling between local structure and ion uptake. These measurements demonstrate that the identity of the compensating ion and its interaction with the polymer and solvent are important considerations for benchmarking and designing polymer materials for mixed ionic/electronic conduction applications.

The electrochemical doping/dedoping kinetics, and the organic electrochemical transistor (OECT) performance of a series polythiophene homopolymers with ethylene glycol units in their side chains using both kosmotropic and chaotropic anion...

We study the organic electrochemical transistor (OECT) performance of the ladder polymer poly-(benzimidazobenzophenanthroline) (BBL) in an attempt to better understand how an apparently hydrophobic side-chain-free polymer is able to operate as an OECT with favorable redox kinetics in an aqueous environment. We examine two BBLs of different molecular masses from different sources. Regardless of molecular mass, both BBLs show significant film swelling during the initial reduction step. By combining electrochemical quartz crystal microbalance gravimetry, in-operando atomic force microscopy, and both ex-situ and in-operando grazing incidence wideangle X-ray scattering (GIWAXS), we provide a detailed structural picture of the electrochemical charge injection process in BBL in the absence of any hydrophilic side-chains. Compared with ex-situ measurements, in-operando GIWAXS shows both more swelling upon electrochemical doping than has previously been recognized and less contraction upon dedoping. The data show that BBL films undergo an irreversible hydration driven by the initial electrochemical doping cycle with significant water retention and lamellar expansion that persists across subsequent oxidation/ reduction cycles. This swelling creates a hydrophilic environment that facilitates the subsequent fast hydrated ion transport in the absence of the hydrophilic side-chains used in many other polymer systems. Due to its rigid ladder backbone and absence of hydrophilic side-chains, the primary BBL water uptake does not significantly degrade the crystalline order, and the original dehydrated, unswelled state can be recovered after drying. The combination of doping induced hydrophilicity and robust crystalline order leads to efficient ionic transport and good stability.

Fiber-shaped dye-sensitized solarc ells have attracted increasingi nteresti np owering wearable and portable electronic devices. However,t he use of liquid electrolytes gives rise to vulnerabilities, greatly limiting their practical applications. Here we develop as table gel electrolyte based on polymer-ionic liquid gel with high nonvolatility and durability.T he gel electrolyte maintains aq uasi-solid state from room temperature to 98 8Ca nd can sustain high temperatures up to 300 8C. Based on this gel electrolyte, the resulting fiber-shaped dye-sensitized solar cell achieves ap ower conversion efficiency of 5.47 % that remains at 90 %a fter 30 days. The gel electrolyte makes the device more environmentally adaptive and compatible to bending and stretching deformations.With the rapid development in moderne lectronics, portable and wearabled evices attractm ore and more attention in our life. Yeti tr emains challenging to power them as the current power systems appear in planar or bulky structures that are incompatible with the required weaveability.Anew family of fiber-shaped energy harvesting and storage devices have been recently created to solve this problem.[1] For instance, fibershaped dye-sensitized solar cells (DSSCs) have been widely studied to produce high powerc onversion efficiencies up to 8.45 %.[2] However,t he use of liquid electrolytes bringss everal drawbacks, including the toxicitya nd inflammability of organic solvents and the leakage and vaporization of liquid electrolytes with the decay of powerc onversion efficiencies.[3] On one hand, many efforts have been devoted to explore ionic liquids (ILs), which are nonvolatile and avoid vaporization,b ut still suffer from the problem of leakage. [3,4] On the other hand, gel electrolytes employing solvents with high boilingp oints such as 3-methoxypropionitrile (MPN) have been studied due to ad eformable structure with no fluidity, [5] avoiding leakage as well as making them promising candidates for flexible devices.[6] However,t he vaporization problem which is detrimental for practical applications still remains due to the volatile nature of organics olvents.[7] Furthermore,t he hygroscopicity of nitrile or other solvents used in gel electrolytes would also shorten the lifetimeo fD SSCs.[8] Replacing the organic solvents by solid-state electrolytes such as IL crystalsc an sufficiently avoid the leakagea nd vaporizationp roblem, [9] and the hydrophobic nature of plastic crystals also provides resistance to water, [10] but the largely decreased current carrierm obility generally lowerst he power conversion efficiencies of DSSCs.[11] In addition, the hardnesso fI Lc rystals sacrifices the flexibility and stretchability of the resulting devices, which is disadvantageous for wearable and portable applications.Herein, an ovel gel electrolyte is developedf rom polymer and hydrophobic ionic liquid to fabricate stretchable fibershaped DSSCs. Poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) copolymer has been chosen to be the gelata in this...

Unlike naphthalene diimides, perylene diimides, and other classes of n-type conjugated polymers with numerous derivatives that enable understanding of structure–property relationships, the electronic structure and properties have not been reported for any derivative of ladder poly­(benzimidazobenzophenanthroline) (BBL). Herein, we report the synthesis and properties of BBL-P, a phenazine derivative of BBL. In acid solution, BBL-P has a broad absorption spectrum with a lowest energy absorption peak at 840 nm due to protonation-enhanced intramolecular charge transfer. Compared to BBL, BBL-P thin films have decreased crystallinity with face-on molecular orientations on substrates, resulting in a substantially decreased field-effect electron mobility of 1.2 × 10–4 cm2/V s. BBL-P films have excellent mechanical properties exemplified by a Young modulus of 11 GPa. The results demonstrate that BBL-P is a promising n-type semiconducting polymer and provide new insights into the effects of backbone structure on electronic structure, thin film microstructure, and charge transport properties of conjugated ladder polymers.