High Thermoelectric Performance in p-Type Polycrystalline SnSe Enabled by Efficient Li Doping via Carrier Engineering

Polycrystalline SnSe is more favorable for practical applications compared with its single-crystalline counterpart due to its easier scalability and mechanical robustness. However, its TE performance is limited by poor electrical transport properties, resulting in a low carrier concentration and modest power factor. Here, we demonstrate both theoretically and experimentally that alkali metal Li doping serves as an effective carrier engineering strategy to overcome performance limitations. First-principles calculations reveal that Li acts as an efficient acceptor, inducing a significant charge transfer and modifying the electronic structure. Experimentally, doping Li increases the carrier concentration 2 orders of magnitude up to 1.8 × 1019 cm–3, resulting in significantly enhanced electrical conductivity and a peak power factor of 7.1 μW cm–1 K–2. Eventually, a high zT value of ∼2.0 at 823 K is achieved in Li-doped SnSe. This work offers important insight for the rational design of high-performance polycrystalline SnSe.