Exceptional Plasticity in Textured Thermoelectric Bismuth Semimetal

Recently flexible thermoelectrics have attracted great attention because they can provide a long‐term and maintain‐free power supply technology to wearable electronics. Current flexible thermoelectrics are mainly based on the narrow bandgap inorganic semiconductors with a high power factor ( PF ) or organic polymers with good flexibility. Although bismuth (Bi) semimetal also possesses high PF , its inherently poor plasticity/ductility greatly limits the achievement of good flexibility. In this work, it is shown that the brittle polycrystalline Bi can be transformed into plastic/ductile via strengthening the texturization by using the mechanical rolling method. The plastic/ductile Bi demonstrates extraordinary flexibility while retaining high PF up to 27 µW cm −1 K −2 at room‐temperature, a record‐high value among reported plastic polycrystalline thermoelectric materials. The in‐plane flexible Bi/Pt‐Rh thermoelectric device shows a high normalized material's maximum power density of 0.42 W m −1 under a temperature gradient of 30 K. This work provides an effective but general strategy to engineer the traditional TE materials from brittle to plastic.