Sandwiched Graphene/Bi₂Te₃/Graphene Thermoelectric Film with Exceptional Figure of Merit for Flexibility

Abstract

Flexible thermoelectrics (TEs) that fit curved human skin well, could harvest energy from skin, and thus have been considered as a promising portable power source for wearable electronics. Bi2Te3, the most popular room‐temperature TE material, is still challenging to be applied in flexible devices due to its rigid nature. Although many Bi2Te3‐based films have been reported to be flexible when made thin enough, the thermal and electrical loads across them are rather small with severe limitation on the maximum power output. This work realizes a thick Bi2Te3‐based TE film with a “graphene/Bi2Te3/graphene” sandwiched structure, which demonstrates an unprecedentedly high figure of merit for flexibility among all Bi2Te3‐based films ever reported, due to the outstanding intrinsic flexibility of graphene and a small slippage barrier. Meanwhile, graphene acts as express conducting channels as well as carrier donors, resulting in an increased electrical conductivity. The numerous graphene/Bi2Te3 heterointerfaces induce energy filtering effect, leading to an enhanced Seebeck coefficient, and thus an optimized power factor is achieved. This work offers a cost‐effective avenue to make highly flexible TE films for power supply of wearable electronics by intercalating TE nanoplates into 2‐dimensional nanosheets.

MXene Nanosheet/Organics Superlattice for Flexible Thermoelectrics

“…Compared with traditional lithium-based batteries, flexible TEs are free of safety concerns because they are maintenance free and need no on-grid recharging. Therefore, they have been attracting intensive research interest. − The conversion efficiency of TE devices is determined by the TE figure of merit, zT = S 2 σ T /κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity; the comprehensive electronic transport indicator is termed the power factor (PF) = S 2 σ. Besides having a good TE performance, TE materials are required to be lightweight, nontoxic, and flexible for wearable applications.…”

From Brittle to Ductile: A Scalable and Tailorable All-Inorganic Semiconductor Foil through a Rolling Process toward Flexible Thermoelectric Modules

“…Figure-of-merit for flexibility. Compared with several literature data of flexible TE materials (graphene/Bi 2 Te 3 , cellulose/Bi 2 Te 3 , three-dimensional graphene/polyaniline, and Ag 2 Se/CuAgSe/Ag on a flexible nylon substrate, our Ag 2 (S/Se/Te) foils exhibit both high ZT and f FOM simultaneously.…”

“…The f FOM values of our ductile foils are in the range of 0.02–0.13, much higher than other flexible materials with competent ZT values, which can explain the similar ductility and malleability in comparison with metal materials. The contrast with other flexible materials can illustrate the superiority of our silver chalcogenide foils with both high ZT values and superior flexibility, suggesting promise for application in next-generation flexible TEGs. − …”

Insights into Interfacial Thermal Resistance in Bi2Te3/Graphene Composites for Thermoelectric Applications

“…Ahmad et al 15 fabricated Bi 2 Te 3 -based graphene nanocomposites with graphene volume fraction ranging from 0.5 to 1.5% and observed considerable enhancement in the thermoelectric figure of merit due to improvement in power factor and the reduction in thermal conductivity. Most recently, Mao et al 18 synthesized a Bi 2 Te 3 -based thermoelectric film with a "graphene/Bi 2 Te 3 /graphene" sandwiched structure, which exhibited the highest ZT for flexibility among all Bi 2 Te 3 -based films ever reported and could be used in thermoelectric generator for flexible electronic devices.…”