N-type Bi-doped SnSe Thermoelectric Nanomaterials Synthesized by a Facile Solution Method.

An n-type Bi-doped SnSe was synthesized by a facile solution method followed by spark plasma sintering. We used bismuth(III) 2-ethyhexanoate as a cationic dopant precursor, which can absorb on the powder surface and then diffuse into the lattice to realize the substitution of Sn by Bi. A strip structure with low-angle boundary was constructed for effective phonon scattering. With increasing content of Bi, the carrier concentration decreased from 1.35 × 1019 cm-3 (p-type) in undoped SnSe to 4.7 × 1014 cm-3 (n-type) in Sn0.99Bi0.01Se and then increased to 1.3 × 1015 cm-3 (n-type) in Sn0.97Bi0.03Se. The Seebeck coefficient changed from positive to negative and presented n-type conducting behavior in the whole measured temperature range from 300 to 773 K, reaching a maximum absolute value of ∼900 μV K-1 at room temperature and ∼300 μV K-1 at 773 K. Considering the rich variety of metal 2-ethylhexanoates, higher thermoelectric performance is expected by different cationic doping in solution-synthesized nanomaterials.