Soft Organic Thermoelectric Materials: Principles, Current State of the Art and Applications

Abstract

heat engines and transforming the asgenerated mechanical energy into electricity. [2][3][4][5] Compared with traditional unsustainable method, thermoelectric materials, which can transform the temperature gradient from waste heat or solar thermal energy into electricity through the Seebeck effect, have triggered great interest in the development of wearable cooling/heating devices and low-temperature energy generators. [6][7][8][9][10][11][12][13][14][15][16][17] Inorganic thermoelectric materials exhibit superior thermoelectric figure of merit than the organic ones, but their low abundance, high-cost, heaviness, and brittleness usually prevents their applications for flexible and/or nontoxic devices. [18][19][20][21][22][23][24] In contrast, organic thermoelectric materials present intrinsically low thermal conductivity and high mechanical flexibility, making them versatile in green energy harvesting and thermoelectric refrigeration (Figure 1). [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] The energy conversion efficiency of the thermoelectric materials can be estimated by the dimensionless figure of merit ZT = S 2 σT/κ, where S is the thermopower or Seebeck coefficient, σ is electrical conductivity of materials, T is the absolute temperature, and κ represents the thermal conductivity. [43][44][45][46][47][48][49][50][51] Superficially, increasing S and σ, and decreasing κ can infinitely raise the value of ZT. However, the strong interdependence among these three parameters is extremely challenging. [52][53][54][55][56] Over the past years, scientists have managed to increase the ZT values of organic thermoelectric materials via molecular design, phonon, and electron transport decoupling, and production of hybrid composites incorporating high thermoelectric particles. [57][58][59][60][61][62][63][64][65][66][67][68][69] In this review, the thermoelectric performances of the organic single-component materials, hybrid composites, and novel ionogels developed over the last several years are discussed separately in terms of the respective parameter tuning and pathway optimization. The current state of the art of organic thermoelectric materials is primarily highlighted based on their structure-property relationship. In particular, the marvelous progress that has allowed organic thermoelectric materials to compete with traditional inorganic compounds is described. Finally, organic thermoelectric generators containing different legs with variousoutput powers and their multiple applications are briefly summarized.The enormous demand for waste heat utilization and burgeoning ecofriendly wearable materials has triggered huge interest in the development of thermoelectric materials that can harvest low-cost energy resources by converting waste heat to electricity efficiently. In particular, due to their high flexibility, nontoxicity, cost-effectivity, and promising applicability in various fields, organic thermoelectric materials are drawing more attention compared with their toxic, expensive, he...

In Situ Observation of Morphological and Oxidation Level Degradation Processes within Ionic Liquid Post-treated PEDOT:PSS Thin Films upon Operation at High Temperatures

“…Whether in lightweight organic photovoltaics, − flexible organic light-emitting diodes, − organic sensors, − organic field-effect transistors, − transparent organic electrodes, − or organic thin-film thermoelectrics, − nowadays, organic semiconductors play a fundamental part in the development of new trendsetting devices and applications. The reason for this lies in the advantageous properties of organic semiconductors, like their easy and low-temperature processability from solution, facilitating a low-cost and energy-efficient fabrication with large-scale deposition techniques like printing, spray, or dip coating. , Furthermore, the raw materials are usually abundantly available and enable low or nontoxic, lightweight, and mechanical flexible devices.…”

Recent Advances and Prospects of Small Molecular Organic Thermoelectric Materials

“…As one of the emerging energy materials, the thermoelectric (TE) materials could convert low‐grade waste heat that cannot be completely utilized into electrical energy in a large area, which is a class of promising candidate materials for relieving energy shortages and reducing the environmental pollution. [ 1–7 ]…”

“…As one of the emerging energy materials, the thermoelectric (TE) materials could convert low-grade waste heat that cannot be completely utilized into electrical energy in a large area, which is a class of promising candidate materials for relieving energy shortages and reducing the environmental pollution. [1][2][3][4][5][6][7] TE materials consist of inorganic thermoelectric (ITE) ones and organic thermoelectric (OTE) ones. Currently, traditional TE materials mainly depend on high-performance inorganic Small molecular OTE materials belong to a branch of OTE materials.…”

Advances in Thermoelectric Composites Consisting of Conductive Polymers and Fillers with Different Architectures

“…Thermoelectric (TE) materials are able to interconvert between heat and electricity based on the Seebeck effect and Peltier effect ( Figure 1 ), which has been found for over 100 years [ 5 ]. TE devices possess plenty of properties such as no noise, no vibration, no gaseous emission, widespread waste heat sources, etc., and can be evaluated by the figure of merit ZT = S 2 σT/κ (1), which is dimensionless, where S is Seebeck coefficient, σ is the electrical conductivity of materials, T is absolute temperature, and κ is the thermal conductivity [ 6 , 7 ]. Although TE materials are promising and have lots of advantages, predominant inorganic TE materials (such as Sb 2 Te 3 , Bi 2 Te 3 , etc.)…”