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

Abstract

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.

Towards Integration of Two-Dimensional Hexagonal Boron Nitride (2D h-BN) in Energy Conversion and Storage Devices

“…One approach to enlarge the band gap of GeP 3 is capping 2D h-BN layer as an insulating material, preserving the in-plane electrical conductance of GeP 3 . As illustrated in Figure 9b-e, GeP 3 is an indirect bandgap material with E g of 0.23 and 0.12 eV for monolayer (1L) and bilayer (2L) GeP 3 , respectively [141]. These values increase to 0.34 eV when a monolayer 2D h-BN is inserted.…”

“…Recently, it was shown that heterostructures of 2D h-BN and 2D GeP 3 can be promising thermoelectric materials [141]. Pristine GeP 3 depicts supreme charge carrier mobility and good chemical stability; however, its small bandgap degrades the thermoelectric characteristics.…”

Double-dome superconductivity in germanium phosphides

“…GeP, GeP 3 , GeP 5 ). [27][28][29][30] Recently, we reported a reversible superconductivity up to the maximum value of 10.5 K at 13.5 GPa during the 2D to 3D structural transition in GeP 5 . 31 More interestingly, a significant phonon softening in the Raman spectrum was observed because of the extension of the inplane P-P bonds.…”

Germanium‐based monoelemental and binary two‐dimensional materials: Theoretical and experimental investigations and promising applications

“…In the GeP 3 /h‐BN heterostructure, by applying 5% tensile strain to adjust the CB structure, a large ZT value of 1.15 at 300 K can be reached for the n‐type heterostructure. For p‐type doping, the highest ZT value of 5.13 was predicted at room temperature in the GeP 3 /h‐BN heterostructure 550 …”

“…For p-type doping, the highest ZT value of 5.13 was predicted at room temperature in the GeP 3 /h-BN heterostructure. 550 F I G U R E 2 4 Solar cells. (A) Schematic configuration of CdS/GeSe superstrate solar cell.…”