High Carrier Mobility Promotes In-Plane Thermoelectric Performance of n-Type PbSnS₂ Crystals

PbSnS₂ crystals have the advantage of high performance and low cost as emerging thermoelectric materials. Herein, thermoelectric properties of PbSnS₂ crystals are substantially boosted through the strategy of lattice plainification to manipulate micro-defect. By introducing Ni elements into n-type PbSnS₂, the intrinsic Pb/Sn cation vacancies are compensated by Ni, achieving a plainer lattice and higher carrier mobility. Meanwhile, the charge density is enhanced due to the orbital hybridization between the 3d orbital of Ni and the 3p orbital of the neighboring S, further facilitating the carrier transport. Consequently, an ultrahigh carrier mobility of ≈312 cm² V⁻¹ s⁻¹ in n-type PbSnS₂+0.0010Ni crystal is obtained with a largely enhanced ZT of ≈0.6 at 300 K along the in-plane direction, and a maximum ZT of ≈1.2 can be obtained at 473 K. Moreover, a 7-pair thermoelectric device composed of n-type PbSnS₂+0.0010Ni crystal and p-type commercial Bi_0.4Sb_1.6Te₃ is fabricated, which can produce a cooling temperature difference of ≈19.4 K. And a single-leg device composed of the PbSnS₂+0.0010Ni crystal realizes a maximum power generation efficiency of ≈2.7%. The work further optimizes the low-cost and earth-abundant PbSnS₂ crystals as potential application candidates in thermoelectric cooling and power generation.