High-Performance μ-Thermoelectric Device Based on Bi₂Te₃/Sb₂Te₃ p-n Junctions

A flexible and ultralight planar thermoelectric generator based on 15 thermocouples composed of n-type bismuth telluride (Bi₂Te₃) and p-type antimony telluride (Sb₂Te₃) legs (each with 400 nm thick) connected in series, on 25 μm thick Kapton substrate, was fabricated with impressive power factor values of 2.7 and 0.8 mW K^-2 m^-1 (at 298 K) for Bi₂Te₃ and Sb₂Te₃ films, respectively. The p-n junction thermoelectric device can generate a maximum open-circuit voltage and output power of 210 mV and 0.7 μW (3.3 mW cm^-2), respectively, for a temperature difference of 35 K, which is higher than the one observed for a conventional thermoelectric device with metallic contacts for p-n junctions. The results were combined with numerical simulations, showing a good match between the experimental and the numerical results. The current density versus voltage (J-V) characteristics of the fabricated p-n junctions revealed a diode behavior with a turn-on voltage of ≈0.3 V and an impressive rectifying ratio (I_+1V/I_-1V) of ≈2 × 10⁴.