Superior Conversion Efficiency Achieved in GeP₃/h-BN Heterostructures as Novel Flexible and Ultralight Thermoelectrics

GeP3 materials are attracting broad research interest due to their typical puckered layer structure, high carrier mobility, and chemical stability. This peculiarity expedites the independent control of anisotropic electrical and thermal conductance, which is thus expected to possess great thermoelectric potential. Nevertheless, the metal characteristics of GeP3 in the bulk and thick films are adverse to real application because of the low Seebeck coefficient. Thus, it is highly desirable to explore effective solutions to broaden the band gap and also maintain its excellent electrical conductance. Herein, we designed the interlaced GeP3/hexagonal boron nitride (h-BN) bulk heterostructure using various component thicknesses. By using ab initio calculations based on the Boltzmann transport theory, we found that capping h-BN layer can obviously increase the band gap of the GeP3 layer by 0.24 eV, and more interestingly, the anisotropic electronic structure in the GeP3/h-BN heterostructure was accordingly modulated toward a favorable direction for high thermoelectricity. An ultrahigh ZT value of around 5 was predicted at 300 K in p-type GeP3/h-BN, attributed to the adjusted multivalley band structure. Overall, our work provided an effective route to design novel high-performance thermoelectrics through the appropriate construction of heterostructures.