▎ 摘　　要

The phonovoltaic cell harvests optical phonons like a photovoltaic harvests photons, that is, a nonequilibrium (hot) population of optical phonons (at temperature T-p,T-O) more energetic than the band gap produces electron-hole pairs in a p-n junction, which separates these pairs to produce power. A phonovoltaic material requires an optical phonon mode more energetic than its band gap and much more energetic than the thermal energy (E-p,E-O > Delta E-e,E-g >> k(B)T), which relaxes by generating electrons and power (at rate (gamma) over dot(e-p)) rather than acoustic phonons and heat (at rate (gamma) over dot(p-p)). Graphene (h-C) is the most promising material candidate: when its band gap is tuned to its optical phonon energy without greatly reducing the electron-phonon (e-p) coupling, it reaches a substantial figure of merit [Z(pV) = Delta E-e,E-g(gamma) over dot(e-p)/E-p,E-O((gamma) over dot(e-p) + (gamma) over dot(p-p)) approximate to 0.8]. A simple tight-binding (TB) model presented here predicts that lifting the sublattice symmetry of graphene in order to open a band gap proscribes the e-p interaction at the band edge, such that (gamma) over dot(e-p) -> 0 as Delta E-e,E-g -> E-p,E-O. However, ab initio (DFT-LDA) simulations of layered h-C/BN and substitutional h-C: BN show that the e-p coupling remains substantial in these asymmetric crystals. Indeed, h-C: BN achieves a high figure of merit (Z(pV) approximate to 0.6). At 300 K and for a Carnot limit of 0.5 (T-p,T-O = 600 K), a h-C: BN phonovoltaic can reach an efficiency of eta(pV) approximate to 0.2, double the thermoelectric efficiency (ZT approximate to 1) under similar conditions.