Unipolar TE performance in bipolar PDPP4T. (a) Hole and electron PF and measured κ_// of doped (40 mmol L⁻¹) PDPP4T film at different temperatures. (b) Resulting PDPP4T unipolar ZT values in the ultra-low temperature regime (below 273 K) and comparison to reported temperature-dependent TE performance of state-of-the-art OTE materials (PMHJ [41], porous PDPPSe-12 [42], DPPBTz [43], PTEG-2 [44], A-DCV-DPTTT [45], K_x(Ni-ett) [46]), whose largest ZT values are mostly at or near room-temperature regime.