Stress-dependent thermoelectric properties in blue-phosphorene-nanoribbon-based heterojunctions

Mechanical strain is a powerful degree of freedom for modulating the thermoelectric performance of quantum structures. Herein, combining density functional theory and the nonequilibrium Green's function method, we systematically investigate the strain-mediated thermoelectric regulation of blue phosphorene nanoribbon heterojunctions (BPNRHJs). The results demonstrate that strain effectively tailors the electrical conductance of monolayer and stacked bilayer BPNRHJs. Specifically, strain shifts the conductance peaks toward the Fermi level at negative chemical potentials and substantially amplifies peak conductance values at positive chemical potentials. Moreover, strain modulates the position and profile of anti-resonant transmission dips induced by destructive quantum coherence, thereby tuning the peak position and enhancing the magnitude of the Seebeck coefficient. Additionally, strained structures exhibit suppressed phonon transmission spectra and reduced phonon transmission coefficients, leading to decreased phonon thermal conductance. Benefiting from the optimized electronic and phononic transport properties, the thermoelectric figure of merit (ZT) is significantly improved. At 500 K, applying strain from 0 to 0.2 GPa increases the maximum ZT from 1.4 to 2.5 for monolayer BPNRHJs and from 1.2 to 2.0 for bilayer BPNRHJs.