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. Bi 2 Te 3 , the most popular room‐temperature TE material, is still challenging to be applied in flexible devices due to its rigid nature. Although many Bi 2 Te 3 ‐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 Bi 2 Te 3 ‐based TE film with a “graphene/Bi 2 Te 3 /graphene” sandwiched structure, which demonstrates an unprecedentedly high figure of merit for flexibility among all Bi 2 Te 3 ‐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/Bi 2 Te 3 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.