Unravelling the potential of a hybrid borocarbonitride biphenylene 2D network for thermoelectric applications: a first principles study

In this study, we investigate a novel hybrid borocarbonitride (bpn-BCN) 2D material inspired by recent advances in carbon biphenylene synthesis, using first-principles calculations and semi-classical Boltzmann transport theory. Our analysis confirms the structural stability of bpn-BCN through formation energy, elastic coefficients, phonon dispersion, and molecular dynamics simulations at 300 K and 800 K. The material exhibits an indirect band gap of 0.19 eV (PBE) between the <b>X</b> and <b>Y</b> points and a direct band gap of 0.58 eV (HSE) at the <b>X</b> point. Thermoelectric properties reveal a high Seebeck coefficient, peaking at 700 V K^-1 for n-type carriers at 200 K along the <i>x</i>-axis, while n-type has a maximum of 588 V K^-1. The electrical conductivity is 2.2 × 10⁷ Ω^-1 m^-1 for hole carriers, surpassing that of conventional 2D materials. The consequences of the high Seebeck coefficient and conductivity reflect a high-power factor with a peak value of 178 × 10^-3 W m^-1 K^-2 at 1000 K for p-type carriers along the <i>y</i>-axis, whereas for n-type carriers, it is 91 × 10^-3 W m^-1 K^-2. Moreover, the highest observed <i>zT</i> values were 0.78 (0.72) along the <i>x</i> (<i>y</i>) direction at 750 K for p-type and 0.57 (0.53) at 750 K along the <i>x</i> (<i>y</i>) axis for n-type. Our findings suggest that the bpn-BCN 2D network holds significant potential for thermoelectric applications due to its exceptional performance.