High electrical transport properties performance enhanced by anti-site defects in single crystalline SnSe

Single crystalline tin selenide (SnSe) has attracted considerable attention due to its record high figure of merit value in medium temperature range. However, their large band gap restricts the electron transport. Herein, we tailor the carrier concentration by offering a variability of the Sn/Se ratio to fine-tune the electrical transport properties. Density functional theory demonstrated that the collaborative optimization of the Seebeck coefficient and the electrical conductivity through optimizing carrier concentration can improve significantly the power factor, and deviation from stoichiometry is an effective strategy to modulate the carrier concentration because anti-site defects SnSe lower the Fermi level and increases the number of carrier pockets in SnSe. Meanwhile, experimental observations confirm that the carrier concentration and electrical conductivity are changed with varied Sn/Se ratio. Through this work, a viable design principle for optimized carrier concentration for achieving high thermoelectric performance is provided.