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 Sn_0.99Bi_0.01Se and then increased to 1.3 × 10¹⁵ cm^-3 (n-type) in Sn_0.97Bi_0.03Se. 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.