Tailoring thermoelectric properties of SnSe thin films through bismuth doping for advanced energy applications

Bismuth-doped SnSe thin films have been synthesized via a simple thermal evaporation route to investigate the influence of Bi incorporation on their structural, morphological and thermoelectric properties. X-ray diffraction confirmed phase purity orthorhombic SnSe with enhanced crystallinity at moderate Bi levels. Scanning electron microscopy revealed that pristine films exhibit granular morphologies, which progressively transform into nanoshaped grains with Bi doping, accompanied by a controlled increase in surface roughness. Hall measurements show that Bi doping raises the carrier concentration from Formula: see text Formula: see textcmFormula: see text (as-grown) to Formula: see text Formula: see textcmFormula: see text (3% Bi), while reducing carrier mobility due to enhanced ionized-impurity scattering. The Seebeck coefficient remains positive across 300–550Formula: see textK, confirming p-type conduction, but decreases from 451.32Formula: see text Formula: see textV KFormula: see text (pristine) to 359.28Formula: see text Formula: see textV KFormula: see text (3Formula: see textat.% Bi) at 300Formula: see textK, consistent with the Pisarenko relationship. In contrast, electrical conductivity increases sharply with Bi content, reaching 240.31Formula: see textScmFormula: see text at 550Formula: see textK for 3Formula: see textat.% Bi. As a result, the thermoelectric power factor rises from 3.1Formula: see text Formula: see text Formula: see textWcmFormula: see textKFormula: see text (pure) to 10.6Formula: see text Formula: see textWcmFormula: see textKFormula: see text for the most heavily doped film at 550 K. These findings demonstrate that moderate Bi incorporation effectively tunes the carrier concentration and optimizes the Seebeck–conductivity balance, offering a cost-effective strategy for enhancing the thermoelectric performance of SnSe thin films.