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

Abstract 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.