Temperature-dependent investigation of the Seebeck p-n switching (S = 0) point. In-situ variable temperature (300 to 50 K). (a) Conductivity and Hall effect, and (b) Seebeck and Nernst effect measurements in 40 mmol L⁻¹ FeCl₃-doped bipolar PDPP4T device. (c) Revealed nonmonotonic temperature dependence of hole and electron partial thermopower in bipolar PDPP4T. The dashed black line represents the measured bipolar thermopower in (b).