Self‐Healable and Stretchable Organic Thermoelectric Materials: Electrically Percolated Polymer Nanowires Embedded in Thermoplastic Elastomer Matrix

Abstract

Self‐healable and stretchable energy‐harvesting materials can provide a new avenue for the realization of self‐powered wearable electronics, including electronic skins, whose main materials are required to be robust to and stable under external damage and severe mechanical stresses. However, thermoelectric (TE) materials showing both self‐healing properties and stretchability have not yet been demonstrated despite their great potential to harvest thermal energy in the human body. As most existing TE materials are either mechanically brittle or unrecoverable after being subjected to damage, a novel approach is necessary for designing such materials. Herein, self‐healable and stretchable TE materials based on all‐organic composite system wherein polymer semiconductor nanowires are p‐doped with a molecular dopant and embedded in a thermoplastic elastomer matrix are reported. The polymer nanowires are electrically percolated in the matrix, and the resulting composite materials exhibit good TE performance. The composites also exhibit both excellent self‐healing properties under mild heat and pressure conditions and good stretchability. It is believed that this work can be a cornerstone for the design of self‐healable and stretchable energy‐harvesting materials as it provides useful guidelines for imparting electrical conductivity to insulating thermoplastic elastomers, which typically possess versatile and useful mechanical properties.

Self‐Healable and Stretchable PAAc/XG/Bi2Se0.3Te2.7 Hybrid Hydrogel Thermoelectric Materials

“…It is noted that the Bi 2 Se 0.3 Te 2.7 can effectively enhance the Seebeck coefficient thus the open‐circuit voltage of PAAc/XG. Compared with the performance of previously reported hydrogel‐based thermoelectric materials, [ 21 ] the Seebeck coefficient of PAAc/XG/Bi 2 Se 0.3 Te 2.7 is higher than that reported in the previous literature ( S = 0.18 mV K −1 ). Figure S5, Supporting Information showed PAAc/XG/Bi 2 Se 0.3 Te 2.7 (1.5 wt%) operating under a common circumstance (60 °C at the hot end and 25 °C at the cold end).…”

Intrinsically Self-Healable and Wearable All-Organic Thermoelectric Composite with High Electrical Conductivity for Heat Harvesting

“…Moreover, the electrical conductivity, Seebeck coefficient, and the power factor present thermal stability in the temperature range from 300 to 370 K. The power factors of all samples increased with increasing temperature due to the increased Seebeck coefficient. At 370 K, the highest power factor of the sample is 6.7 ± 0.8 μW m –1 K –2 , which is much higher (5.8 times) than the reported value of intrinsic self-healing thermoelectrical materials . After self-healing, the maximum power factor slightly decreases to 5.6 ± 0.8 μW m –1 K –2 , indicating that the self-healing film retains 84% of the initial power factor value.…”

“…The output power has a parabolic relationship with the current, reflecting the typical characteristic of series circuits (discharge characteristic). When the temperature gradient is 48 K, the output voltage is 8.02 mV, and the maximum output power ( P MAX ) is 85.5 nW (Figure a), which is a significant advance over the recently reported generators assembled from the stretchable and self-healing thermoelectric materials, as summarized in Figure d. ,,− The theoretical output power (136.7 nW) calculated from eq () is higher than the actual output power (85.5 nW) due to the inevitable contact resistance or temperature measurement error of the component.…”

“…(a) Voltage–current curve and power–current curve of the thermoelectric generator at a temperature difference of 48 K; (b) schematic illustration of the thermoelectric generator; (c) V AC and V TH of the thermoelectric generator at different Δ T s ; (d) power factor and actual output power reported in the literature based on the thermoelectric generator assembled from the stretchable and self-healing thermoelectric materials; ,,− in the composite, the PVA/PEDOT/PSS = 1:15:1, the solid ratio of borax is set as 0.45 wt %, and the volume fraction of PEG is 6 vol %.…”

Enhanced Electrical Conductivity and Mechanical Properties of Stretchable Thermoelectric Generators Formed by Doped Semiconducting Polymer/Elastomer Blends

“…The electrical conductivities of the as-fabricated and previously reported fully flexible/stretchable doped TE devices under various tensile strains are compared in Figure a, and the details are provided in Table S3. Importantly, the as-fabricated p-doped P3HT / SEBS = 90/10 and n- or p-doped PDVT-10 / SEBS = 90/10 films exhibit electrical conductivities approximately 2 orders of magnitude higher than the maximum electrical conductivity observed among the previously reported TE devices. ,,, …”