A co-doping strategy for p- to n-type transition and performance boost in SnSe-based flexible thermoelectric generators

Flexible thermoelectric generators (FTEGs) have garnered considerable interest for their potential in energy harvesting applications. This study investigates the synthesis of SnSe and Bi/Te co-doped SnSe polycrystals using the solid-state reaction method, followed by the fabrication of FTEGs using a low-cost, scalable screen-printing technique. Hall effect measurements confirm successful doping, resulting in a transition from p-type to n-type conduction in SnSe. The Seebeck coefficient of the 2% Bi-doped SnSe/SnSe (p–n type) FTEG reaches −1146 μV K⁻¹, enhancing the thermoelectric performance. A maximum power output of 6.8 nW was obtained for a p–n-type FTEG consisting of SnSe and Sn_0.98Bi_0.02Se_0.97Te_0.03 at a temperature difference of 120 °C. Thermal conductivity measurements indicate that doping reduces phonon transport due to increased microstrain and dislocation density, which enhance phonon scattering. Furthermore, the FTEGs exhibited excellent mechanical stability, with less than 0.5% change in electrical resistance at bending angles up to 120° and after 500 cycles. These results suggest that Bi/Te co-doped SnSe is a potential candidate for scalable, flexible thermoelectric applications.