Substantial enhancement of thermoelectric performance in <i>n</i>-type AgBiSe2<i>via</i> Mn3+ doping

In recent years, I-V-VI2 compounds have attracted significant scholarly attention due to their inherently low thermal conductivity. However, almost no n-type counterpart with a similar rock salt structure has been identified within the I-V-VI2 family. It is worth noting that AgBiSe2 synthesized via the high-temperature solid-state method stands out as one of the rare n-type semiconductors. In this work, the thermoelectric performance of AgBiSe2 was significantly improved by partial substitution of Ag+ upon Mn3+ ions. Electrical conductivity (σ) of Ag1−xMnxBiSe2 (x = 0, 0.015, 0.03, 0.045, 0.06) compounds increases from ∼39 S cm−1 (x = 0, at 727 K) to ∼166 S cm−1 (x = 0.06, at 733 K), while the total thermal conductivity (κt) reduces from ∼0.44 W m−1 K−1 for x = 0 at 727 K to respective ∼0.38 and ∼0.36 W m−1 K−1 for x = 0.03 and 0.015, at 733 K. Accordingly, a maximum thermoelectric figure of merit ZT (ZTmax) value of ∼0.80 is achieved at 733 K for both x = 0.03 and 0.015 samples, representing a substantial improvement by 74% in comparison with the pristine AgBiSe2 (∼0.46 at 727 K). These results demonstrate that the Mn3+ ion doping should be a very promising strategy in designing medium-temperature n-type thermoelectric materials.