Energy filtering and phonon scattering effects in Bi₂Te₃-PEDOT:PSS composite resulting in enhanced n-type thermoelectric performance

We blend n-type Bi2Te3 with an inexpensive abundant conducting polymer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), to gain a bulk-structured composite, in which energy filtering and phonon scattering effects should occur at the interface of two components. The composite records somewhat higher electrical resistivity than pristine Bi2Te3, because the interface possibly interrupts carrier transport. However, the composite completely compensates for the resistivity increment with a significant increase in the Seebeck coefficient, which is caused by energy filtering effects at the interface; thus, it exhibits the improved power factor. The composite also records a much lower thermal conductivity than the pristine Bi2Te3 because of phonon scattering effects at the interface. The composite induces significant decoupling of electrical and thermal properties, thus affording the remarkably enhanced figure of merits (ZTmax ∼1.19 at 132 °C, ZTave ∼1.14 at 50-150 °C), which are approximately double those of the pristine Bi2Te3. The ZT values are not only predominant among the performance of n-type binary Bi2Te3, but they are also as competent as the excellent performance of n-type ternary Bi2(Te,Se)3 previously reported.