p-type Sn0.98Ag0.02Se with low thermal conductivity synthesized by hydrothermal method

Tin selenide exhibits outstanding thermoelectric properties. Among its various forms, multicrystalline SnSe stands out as a more practical choice compared to single-crystal SnSe, owing to its straightforward chemical synthesis process, enhanced processability, and scalability. Herein, we synthesized p-type polycrystalline Sn 1−x Ag X Se bulk materials (x = 0, 0.01, 0.015, 0.02, 0.025, 0.03) using a simple hydrothermal and hot pressing method. Characterization methods such as XRD , Raman and XPS were used to demonstrate the successful doping of Ag + into the SnSe matrix. When the doping concentration reached Sn 0.98 Ag 0.02 Se (x = 0.02), Ag + reached the optimal concentration in the SnSe matrix, causing significant lattice distortion which increased phonon scattering and lowered the thermal conductivity , resulting in Sn 0.98 Ag 0.02 Se achieving ZT max = 1.14. However, when the doping concentration exceeded Sn 0.98 Ag 0.02 Se (x > 0.02), excess silver ions precipitated, partially acting as charge carriers, leading to a significant increase in electrical conductivity , resulting in Sn 0.97 Ag 0.03 Se having an electrical conductivity of 6860 s/m at 773 K. Compared to the pure phase, the electrical conductivity of Sn 0.97 Ag 0.03 Se increased by 259 %, and the ZT value of Sn 0.98 Ag 0.02 Se increased by 178%. This work demonstrates that Ag + is an effective p-type dopant in the SnSe system and indicates that high ZT values in SnSe can be achieved through a simple, low-cost, and environmentally friendly method.