Ultrahigh Thermoelectric Performance Realized in Black Phosphorus System by Favorable Band Engineering through Group VA Doping

Abstract Black phosphorus (BP) has emerged as a promising thermoelectric candidate because of its strong electronic and thermal anisotropy, suggesting a large σ/κ ratio can be realized by controlling carrier transport orientation for a potentially high ZT. Nevertheless, to date, low conversion efficiency (ZT ≈0.08, 300 K) and poor stability of BP remain the major issues that have hampered its practical applications. This work reports a material family in simple composition XP₇, XP₃, and XP (X = N, As, Sb, Bi) with high‐performance thermoelectric properties by first‐principles calculations. Strikingly, an ultrahigh ZT up to 1.21 at 300 K is achieved in p‐type BiP₇ with an optimal carrier concentration of 5.48 × 10¹⁹ cm⁻³ and ZT in n‐type NP₃ can reach up to ≈0.87 at the electron concentration of 3.67 × 10¹⁹ cm⁻³ along the zigzag direction, owing to their enhanced density of states and multivalley band structures around the Fermi level through the resonant effects of VA guest and host atoms. Additionally, the calculations demonstrate further improvement in thermoelectric performance of pristine BP by ≈4.8 and 4.5 times at 800 K in p‐type NP and n‐type NP₃, respectively. Considering the high stability, current results indicate that N–P based systems are highly promising for novel metal‐free, nontoxic, and ultralight thermoelectrics.