Paper Thermoelectrics by a Solvent-Free Drawing Method of All Carbon-Based Materials

Abstract

As practical interest in the flexible or wearable thermoelectric generators (TEGs) has increased, the demand for the high-performance TEGs based on ecofriendly, mechanically resilient, and economically viable TEGs as alternatives to the brittle inorganic materials is growing. Organic or hybrid thermoelectric (TE) materials have been employed in flexible TEGs; however, their fabrication is normally carried out using wet processing such as spin-coating or screen printing. These techniques require materials dissolved or dispersed in solvents; thus, they limit the substrate choice. Herein, we have rationally designed solvent-free, all carbon-based TEGs dry-drawn on a regular office paper using few-layered graphene (FLG). This technique showed very good TE parameters, yielding a power factor of 97 μW m–1 K–2 at low temperatures. The p-type only device exhibited an output power of up to ∼19.48 nW. As a proof of concept, all carbon-based p-n TEGs were created on paper with the addition of HB pencil traces. The HB pencil exhibited low Seebeck coefficients (−7 μV K–1), and the traces were highly resistive compared to FLG traces, which resulted in significantly lower output power compared to the p-type only TEG. The demonstration of all carbon-based TEGs drawn on paper highlights the potential for future low-cost, flexible, and almost instantaneously created TEGs for low-power applications.

Flexible Thermoelectric Generator from Bulk Graphite and Bismuth Traces on Emery Paper

“…Figure 5d shows the I–V characteristics of our six‐pair device for different temperature gradients, which suggest that the fabricated PTEG is a typical linear voltage source. The output power of the device is calculated using the relation P M = ( V oc I sc )/4, [ 38 ] which is ≈14.6 nW for Δ T = 70 K. It is to be noted that our obtained value is very much comparable to the recent literature reports, [ 16,17,19 ] furthermore with added advantages of using simpler and even more economic processing methods. To check the scalability of the PTEG, we extended the device geometry to 60‐pair (device image Figure S7, Supporting Information) and the output performance is shown in Figure 5e,f.…”

“…The RT σ for the bismuth trace is measured as 5.6 S cm À1 and that of the graphite trace is 84.4 S cm À1 (Figure 3a,c). Even at RT, measured value of σ of the graphite trace is several orders higher than that reported for contemporary works on graphite traces on regular paper (6 [16] and 3.3 S cm À1 [17] ), which might be due to extra roughness of the emery paper compared to regular office paper. At RT, σ value for our bismuth trace is however less compared to bulk or thin film.…”

“…[14] In that direction, inorganic film-based paper TEGs (PTEGs) have drawn attention due to their lightweight, foldability, low cost, simplicity in fabrication, improved functionality, environment friendliness, and market readiness. [15][16][17][18][19][20] Increasing research reports on PTEGs invariably suggests that by carefully designing the devices and by manipulating the rigidity of inorganic TE semiconductors, larger output voltages and power and thereby better performance can be obtained and practically implementable for thermal sensing and microenergy harvesting.In the present work, we introduce a highly feasible emery paper-based PTEG composed of graphite as p-type leg and bismuth as n-type leg from their bulk traces, without additional complex growth and processing steps of the constituent TE materials or intermediate chemical modification. We show that just simple bulk tracing method and by choosing proper roughness of the emery paper, an output power as good as 137.5 nW can be obtained for ΔT % 70 K, which is also supported by finite-elemental analysis.…”

“…[14] In that direction, inorganic film-based paper TEGs (PTEGs) have drawn attention due to their lightweight, foldability, low cost, simplicity in fabrication, improved functionality, environment friendliness, and market readiness. [15][16][17][18][19][20] Increasing research reports on PTEGs invariably suggests that by carefully designing the devices and by manipulating the rigidity of inorganic TE semiconductors, larger output voltages and power and thereby better performance can be obtained and practically implementable for thermal sensing and microenergy harvesting.…”

Sensors-on-paper: Fabrication of graphite thermal sensor arrays on cellulose paper for large area temperature mapping

“…Therefore, the current thermoelectric research is focused on finding low-cost and non-toxic thermoelectric conductors for the application [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] . With some improvements and modifications in the thermoelectric properties of graphite such as by organic doping or alloying with other semiconductors, they can also be utilized in the fabrication of thermoelectric devices [19] , [38] , [39] , [40] , [41] , [42] , [43] , [44] , [45] .…”