High performance magnesium-based plastic semiconductors for flexible thermoelectrics.

Low-cost thermoelectric materials with simultaneous high performance and superior plasticity at room temperature are urgently demanded due to the lack of ever-lasting power supply for flexible electronics. However, the inherent brittleness in conventional thermoelectric semiconductors and the inferior thermoelectric performance in plastic organics/inorganics severely limit such applications. Here, we report low-cost inorganic polycrystalline MgSbBiTe, which demonstrates a remarkable combination of large strain (~ 43%) and high figure of merit zT (~ 0.72) at room temperature, surpassing both brittle Bi(Te,Se) (strain ≤ 5%) and plastic Ag(Te,Se,S) and organics (zT ≤ 0.4). By revealing the inherent high plasticity in MgSb and MgBi, capable of sustaining over 30% compressive strain in polycrystalline form, and the remarkable deformability of single-crystalline MgBi under bending, cutting, and twisting, we optimize the Bi contents in MgSbBi (x = 0 to 1) to simultaneously boost its room-temperature thermoelectric performance and plasticity. The exceptional plasticity of MgSbBi is further revealed to be brought by the presence of a dense dislocation network and the persistent Mg-Sb/Bi bonds during slipping. Leveraging its high plasticity and strength, polycrystalline MgSbBi can be easily processed into micro-scale dimensions. As a result, we successfully fabricate both in-plane and out-of-plane flexible MgSbBi thermoelectric modules, demonstrating promising power density. The inherent remarkable plasticity and high thermoelectric performance of MgSbBi hold the potential for significant advancements in flexible electronics and also inspire further exploration of plastic inorganic semiconductors.