As conventional organic solvents present inherent toxicity, deep eutectic solvents (DES) have been considered as excellent candidates due to their green characteristics. In this work, thermoelectric properties enhancement of PEDOT:PSS films is achieved by introducing DES as an additive and post‐treatment reagent. Direct addition and post‐treatment approaches lead to a maximum Seebeck coefficient of 29.1 μV K⁻¹and electrical conductivity of 620.6 S cm⁻¹, respectively. In addition, an optimal power factor is obtained by DES post‐treatment, reaching up to 24.08 μW m⁻¹K⁻², which is approximately four orders of magnitude higher than the pure PEDOT:PSS. Assuming a thermal conductivity of 0.17 W m⁻¹K⁻¹, the maximum ZT value is estimated to be 0.042 at 300 K. Further, atomic force microscopy and X‐ray photoelectron spectroscopy are performed and suggest that the remarkably enhanced electrical conductivity originates from the removal of the excess insulating PSS and the phase separation between the PEDOT and PSS chains. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 885–892

An effective approach to enhanced thermoelectric properties of PEDOT:PSS films by a DES post‐treatment

Nowadays, the search for novel active materials for laser devices is proceeding faster and faster thanks to the development of innovative materials able to combine excellent stimulated emission properties with low-cost synthesis and processing techniques. In this context, amplified spontaneous emission (ASE) properties are typically investigated to characterize the potentiality of a novel material for lasers, and a low ASE threshold is used as the key parameter to select the best candidate. However, several different methods are currently used to define the ASE threshold, hindering meaningful comparisons among various materials. In this work, we quantitatively investigate the ASE threshold dependence on the method used to determine it in thin films of dye-polymer blends and lead halide perovskites. We observe a systematic ASE threshold dependence on the method for all the different tested materials, and demonstrate that the best method choice depends on the kind of information one wants to extract. In particular, the methods that provide the lowest ASE threshold values are able to detect the excitation regime of early-stage ASE, whereas methods that are mostly spread in the literature return higher thresholds, detecting the excitation regime in which ASE becomes the dominant process in the sample emission. Finally, we propose a standard procedure to properly characterize the ASE threshold, in order to allow comparisons between different materials.

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Amplified Spontaneous Emission Threshold Dependence on Determination Method in Dye-Doped Polymer and Lead Halide Perovskite Waveguides

Ionic conductors are promising candidates for fabricating soft electronics, but currently applied ionic hydrogels and organogels suffer from liquid leakage and evaporation issues. Herein, we fabricated a free-liquid ionic conducting elastomer (LFICE) with dry lithium bis(trifluoromethane sulfonimide) and elastomeric waterborne polyurethane. The resultant versatile LFICE exhibits superior tensile strength (∼4.5 MPa), satisfactory stretchability (>900%), excellent ionic conductivity (8.32 × 10-4 S m-1 at 25 °C), and sensitive strain (3.21) and temperature (2.22% °C-1) response. The LFICE also presents durable environmental stability due to the all-solid-state feature. In the exploration of application prospects, the as-assembled LFICE sensor can precisely and repeatedly detect human motion and temperature changes, demonstrating its potentials in digital medical diagnosis and monitoring; the as-assembled LFICE thermoelectric generator (TEG) shows a high ionic thermovoltage of 4.41 mV K-1, paving a bright path for the advent of self-powered soft electronics. It is believed that this research boosts the facile fabrication of environmental stable stretchable ionic conductors holding great promise in next-generation soft electronics integrated with dual thermo- and strain-response and energy harvesting.

Liquid-Free Ion-Conducting Elastomer with Environmental Stability for Soft Sensing and Thermoelectric Generating.

Poly(3,4ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) has been intensively studied for its thermoelectric applications. Structural modulation to improve crystalline ordering, chain conformation and film morphology is a promising way to decouple the trade-off between conductivity and Seebeck coefficient and thus improve the thermoelectric power factor. Post treatment with ionic liquid ([CoCl2  ⋅ 6H2 O]:[ChCl]) bearing cobalt-containing anions resulted in a remarkable enhancement of the power factor to 76.8 μW m-1  K-2 . This IL combines the influence of a high-boiling polar organic solvent and diffusing ions. A high σ mainly resulted from the efficient removal of PSS chains, ordering of the structure and delocalization of bipoloran-dominant transport after conformational change. The increase in S was not due to dedoping of PEDOT chains, but rather the sharp feature of the density of states at the Fermi level induced by ion-exchange with unconventional anions.

Structural modulation induced by cobalt-based ionic liquids for enhanced thermoelectric transport in PEDOT:PSS.

This article presents PEDOT:PSS/cholinium IL composites to design safe bioelectrodes for long-term cutaneous recording. The PEDOT:PSS/IL composites presented improved electronic and ionic conductivities, as well as injectable properties.

Injectable PEDOT:PSS/cholinium ionic liquid mixed conducting materials for electrocardiogram recordings

Biocompatible, flexible and conductive polymers prepared by biomass-derived ionic liquid treatment

Inorganic cesium lead halide perovskite (CsPbX3, X = Cl, Br, and I) has attracted increasing attention in the field of laser application due to its excellent stability compared to the organic–inorganic hybrid perovskite since affording the radiation of a long pulse pump source requires high thermal stability of the material. However, it is difficult to observe the amplified spontaneous emission (ASE) of CsPbBr3 using a one-step solution method due to the low solubility of CsBr in the organic solvent. Herein, we fabricate a CsPbBr3 film with a two-step solution method and realize the ASE under the long pulse pumping. Meanwhile, a CsBr aqueous solution is used as an effective additive to increase the concentration of Cs+ in the precursor solution and then to improve the optical amplification properties of the CsPbBr3 films. The films exhibit better crystalline and enhanced photoluminescence intensity. Both the ASE threshold and gain have been significantly improved. Furthermore, the optimized film shows a satisfying stability of ASE after being placed in the air for more than two months.

Air-stable and low threshold amplified spontaneous emission via CsBr aqueous solution processed all-inorganic CsPbBr3 perovskite films

Organic additives can enhance the amplified spontaneous emission (ASE) performance of inorganic cesium lead halide perovskites (CsPbBr3 ) but volatility, potential hygroscopicity and oxidative degradation of these additives jeopardizes the thermal stability and shelf-life of blended CsPbBr3 films. To address this problem, we have fabricated perovskite films in a two-step solution protocol involving as little added polyethylene oxide (PEO) as possible. These films exhibited enhanced crystallization, improved photoluminescence (PL) intensity and prolonged lifetimes. Their hierarchical morphology and surface passivation lowered the ASE threshold from 278 to 176 μЈ/cm2 under one-photon nanosecond laser excitation. The proportion of added PEO was 0.3 wt% and was subsequently almost fully removed, thereby reducing its adverse influence on the stability of resulting films under continuous pulsed laser excitation. Stable ASE spectra could be stimulated after storage in air for 10 months.

Ruqing Liu

Papers

Biocompatible, flexible and conductive polymers prepared by biomass-derived ionic liquid treatment

Air-stable and low threshold amplified spontaneous emission via CsBr aqueous solution processed all-inorganic CsPbBr3 perovskite films

Low-Threshold Amplified Spontaneous Emission from Air-Stable CsPbBr3 Perovskite Films Containing Trace Amounts of Polyethylene Oxide.