Stretchable materials are essential for next generation wearable and stretchable electronic devices. Intrinsically stretchable and highly conductive polymers (termed ISHCP) are designed with semi interpenetrating polymer networks (semi-IPN) that enable polymers to be simultaneously applied to transparent electrodes and electrochromic materials. Through a facile method of acid-catalyzed polymer condensation reaction, optimized ISHCP films show the highest electrical conductivity, 1406 S/cm, at a 20% stretched state. Without the blending of any other elastomeric matrix, ISHCP maintains its initial electrical properties under a cyclic stretch-release of over 50% strain. A fully stretchable electrochromic device based on ISHCP is fabricated and shows a performance of 47.7% ∆T and high coloration efficiency of 434.1 cm2/C at 590 nm. The device remains at 45.2% ∆T after 50% strain stretching. A simple patterned electrolyte layer on a stretchable electrochromic device is also realized. The fabricated device, consisting of all-plastic, can be applied by a solution process for large scale production. The ISHCP reveals its potential application in stretchable electrochromic devices and satisfies the requirements for next-generation stretchable electronics.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a promising conducting polymer in terms of its applicability to transparent and flexible electronic devices. Generally, a negatively charged PSS chain can interact with alkali metal cations like sodium and potassium. During polymerization, these ions, especially sodium ions, remain in an aqueous state and affect particle formation. This paper describes the effect of residual sodium ions on the synthesis of PEDOT:PSS and its electrical and optical properties. Removing the sodium ions weakens the coulombic interaction between the PEDOT and PSS chains, which leads to a linear conformation. This conformational change enhances the electrical conductivity and work function. Furthermore, transmittance in the visible region increased remarkably because the intrinsic electrical properties of the PEDOT:PSS particles were improved. Moreover, the colloidal stability was enhanced because the particle coagulation caused by residual sodium ions was reduced. In summary, we determined that sodium ions in PEDOT:PSS have a considerable influence on its electrical and optical properties and colloidal stability for practical applications.

(3,4-Ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a representative conducting polymer, is environment-friendly and offers easy processing and flexibility owing to its hydro-dispersive properties.

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Electrochromic devices (ECDs) exhibit significant potential as emerging electronics for applications associated with smart windows. They can dynamically control solar radiation consumption in buildings and vehicles to enhance efficiency. However, because smart windows are not optimized for high performance, and most are manufactured based on glass form, the large-area manufacturing process is complex and hinders its applicability to electrochromic (EC) devices. In this study, an ECD was fabricated on a PET film by a solution process using a multifunctional conducting polymer synthesized by oxidation polymerization. The polymer layer used was PEDOT:PSS and PANI:PSS, which alone can serve as an electrode and an EC layer, without the need for other electrode materials (ITO, FTO, etc.). The ECD showed excellent optical characteristics and cycle stability owing to the balanced surface charge capacity (insertion/exertion). An excellent coloration efficiency value (1872.8 cm2 C–1 at 600 nm) was obtained with low-power consumption (102 μW cm–2 (coloration) and 11 μW cm–2 (bleaching)). The characteristics of these materials and devices have significant applicability as large-area smart windows. When fabricated using the roll-to-roll method, a large-area smart window of 500 × 500 mm2 was produced. The heat-shielding characteristics (86.2%) were also excellent. Very good energy-savings were achieved and an all-organic smart window with excellent characteristics was verified. The capability of solution and low temperature processing for ECDs has the ability to significantly influence the industrialization of large-area smart windows.

PEDOT:PSS linearity enhancement using controlled addition process.

Conjugated polymers are desired as organic electrode materials because of their functional properties such as solution process, low cost, and transparency. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), in particular, shows the highest applicability, but its heterogeneous structure presents limitations in terms of electrical conductivity. In this study, a facile method to fabricate multi-layered thin films with higher ordered structures was developed. Through the etching process with H2SO4 and dimethyl sulfoxide(DMSO), the insulated rich-PSS was removed from the upper layer to improve its electrical properties and rearrange the PEDOT molecular structures. The thickness of PEDOT:PSS thin films was experimentally optimized to maximize the enhancement of carrier mobility via a layer-by-layer (LBL) process. The combined method, consisted of etching and the LBL process, showed the improvement of the charge carrier mobility from 0.62 to 2.80 cm2 V−1 s−1. The morphology and crystallinity of the ordered PEDOT:PSS structure were investigated by X-ray photoemission spectroscopy (XPS), Raman, and X-ray diffraction (XRD). As a result, two-dimensional lamellar-stacked PEDOT:PSS thin films were fabricated through the repetitive etching and LBL process. The optimized PEDOT:PSS thin film showed an excellent electrical conductivity of 3026 S cm−1, which is 3.8 times higher than that of the pristine film (801 S cm−1).

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has the merits of high electrical conductivity and solution processability, and can be dispersed in water. To improve the stretchability of PEDOT:PSS-based transparent electrode films, the intrinsically conducting polymer PEDOT:PSS was blended with highly stretchable nonionic waterborne polyurethane (WPU) and coated on a thermoplastic polyurethane (TPU) film. Nonionic WPU has good compatibility with PEDOT:PSS, without affecting the acidity. WPU undergoes hydrogen bonding and coulombic attractions with PEDOT:PSS. With variation of the WPU content, differences in the electrical properties, such as the sheet resistance and mechanical stretchability, of the coated thin films were observed. The film with 2.0 wt% WPU could be stretched to 400% of the electrode surface without damage to the surface of the electrode films. The WPU and TPU films both have a polyester group, which provides good adhesion between the WPU-based transparent electrodes and the TPU substrate films. A stretchable alternating current electroluminescence (ACEL) device was constructed by using the water-based PEDOT:PSS/nonionic WPU composite as both the bottom and top transparent electrodes. The fabricated ACEL remained its initial luminance in the 500% stretched state.