fig6

Figure 6. Conversion efficiency measurement of a Mg_3+δBi_1.5Sb_0.5/Bi_0.4Sb_1.6Te₃ unicouple with the cold-side temperature maintained at room temperature. (A) Unicouple measurement setup. Input current relationship with (B) open circuit voltage, (C) output power, (D) heat flow out of the cold side, and (E) conversion efficiency at different hot-side temperatures. (F) comparison of conversion efficiency between this work and recently reported devices operating at near room temperatures (Mg₃Sb₂/Bi₂Te₃^[6], Bi₂Te₃-based device^[9], segmented Mg₃Sb₂/MgAgSb^[38], Mg₃Bi₂/MgAgSb^[40], and Mg₃Sb₂/MgAgSb^[43]).