3D cellulose fiber networks modified by PEDOT:PSS/graphene nanoplatelets for thermoelectric applications

Abstract

Organic materials have attracted considerable attention for thermoelectric (TE) applications. Given their potential as wearable power generators, there is an urgent need to develop organic TE materials that possess superior electronic properties as well as excellent mechanical and environmental stability. Here, we develop paper-based TE materials using the PEDOT:PSS, graphene nanoplatelets (GNPs), and a starch-based biopolymer as a binder for GNPs. The device fabrication consists of spraying the biopolymer/GNPs ink onto the cellulose paper followed by spraying the PEDOT:PSS solution. Further enhancement of the TE properties was obtained by adding an ionic liquid (IL), bis(trifluoromethane)sulfonimide lithium salt (LiTFSI), to the PEDOT:PSS solution. Upon the addition of the IL, the electrical conductivity of the as-fabricated PEDOT:PSS films increased nearly two orders of magnitude. The electrical conductivity increases with GNPs content due to the formation of an effective electrical percolation network. Interestingly, incorporating GNPs simultaneously improves the Seebeck coefficient. Raman measurements suggest that the concurrent enhancement of the Seebeck coefficient and electrical conductivity might be related to the chemical bonding between the conducting polymer chains and the filler. In addition, these composites display remarkable flexibility at various bending angles and environmental stability without losing their original conductivity after three months of exposure to ambient conditions. Recently, organic TE materials have drawn considerable attention for room temperature waste heat recovery. Unlike inorganic materials, they have several advantages such as high flexibility, low thermal conductivity, nontoxicity, low cost, lightweight, and high solution processability 3 . In particular, they are of interest for the development of self-powered wearable devices, as they can generate electrical power from human body heat. Examples of such applications include functional artificial skin, health monitoring devices, and wearable sensors 4 . Among the conducting polymers, poly(3,4-ethylenedioxythiophene) doped with polystyrenesulfonate (PEDOT:PSS) is the most studied and explored organic TE material. Owing to the unique properties such as flexibility, water-solubility, high electrical conductivity, high work function, good environmental stability, and excellent processability, PEDOT:PSS has become the most promising organic TE material 5 . The PEDOT:PSS has a core-shell structure with a conducting positively charged PEDOT core and an insulating negatively charged PSS shell. After annealing the film, the polymer exhibits a globular grainlike structure from the composition of the PEDOT chains and PSS domains. However, the PSS domains negatively affect the electrical conductivity of pristine PEDOT:PSS. There are several strategies to increase the electrical conductivity of PEDOT:PSS such as increasing the crystallinity, inorganic hybridization, and replacing or removing PSS components 5 .

Interfacial Effect Boosts the Performance of All‐Polymer Ionic Thermoelectric Supercapacitors

“…According to literature, the particles and elongated features represent the conducting parts and insulating domains of PEDOT:PSS, respectively. [ 18–20 ]…”

“…According to literature, the particles and elongated features represent the conducting parts and insulating domains of PEDOT:PSS, respectively. [18][19][20] Simple vertical supercapacitor structures are composed of the ion gel between two electrodes of either PEDOT:PSS or AuNWs (Figure 2a). The ability of those electrodes to store charges is investigated by the cyclic voltammetry (CV) and galvanic charge-discharge (GCD) techniques (Figure S2, Supporting Information).…”

Solution processed organic thermoelectric generators as energy harvesters for the Internet of Things

“…147 Cotton and cellulose have been used as a host for active materials with mixed results. [147][148][149] Cataldi et al have shown that similar fiber-based TEGs can be realized by spray-coating cotton fibers with a mixture of doped nanocarbon species (active material) and aleuritic acid (binder) to produce a biodegradable composite for thermoelectric applications. 147 The proof-of-concept TEG made entirely from the organic textile-based thermocouples yielded a maximum power output of %1.0 nW at DT ¼ 70 K. 147 Spraycoated or solution-soaked thermoelectric fibers also have the benefit of being extremely scalable.…”

Review on PEDOT:PSS-Based Conductive Fabric

“…PEDOT:PSS conductive fibers have relatively high electrical conductivity, , stability, and charge storage, which is why they are used for many high-tech applications, such as smart textiles, , flexible electrodes, , sensors, , and actuators . PEDOT:PSS can be spun into a conductive fiber or filament or can be produced during wet spinning , or electrospinning of fibers …”