Rollable Single‐Piece Thermoelectric Generators at Cryogenic Temperature Fabricated with High‐performance CNT Films Achieved by Doping Modulation

Thermoelectric generators (TEGs) can convert heat to electricity through all-solid-state structure, which makes them suitable for energy recovery in cold environments. However, cryogenic TEG development faces dual challenges: severe power factor (PF) degradation and interfacial failures due to thermal expansion mismatch at module-electrode junctions. In this work, a high PF is reported up to 10.5 mW m^-1 K^-2 at room temperature in carbon nanotube (CNT) films achieved by a developed material-processing strategy with an annealing treatment method to carefully optimize the chlorosulfonic acid (CSA) doping level included. This PF value is close to some of state-of-the-art inorganic thermoelectric materials at room temperature, which varies in 20% over a temperature range of 100-298 K that is superior to most of the state-of-the-art inorganic thermoelectric materials (25%-70%). Spectra demonstrate that the CSA doping is a physical adsorption process, which is successfully fitted by the pseudo-second-order kinetic model. In addition, a single-piece rollable TEG is fabricated to mitigate interfacial stresses, and this TEG maintained exceptional flexibility and structural integrity under cryogenic thermal cycling. Furthermore, a miniature thermoelectric power station is fabricated through integrating the rolled TEGs, which demonstrates the promising application of CNT based TEGs in cold environments.