Phonovoltaic. I. Harvesting hot optical phonons in a nanoscalep−njunction

Abstract

The phonovoltaic (pV) cell is similar to the photovoltaic. It harvests nonequilibrium (hot) optical phonons (E p,O ) more energetic than the bandgap (∆E e,g ) to generate power in a p-n junction.We examine the theoretical electron-phonon and phonon-phonon scattering rates, the Boltzmann transport of electrons, and the diode equation and hydrodynamic simulations to describe the operation of a pV cell and develop an analytic model predicting its efficiency. Our findings indicate that a pV material with E p,O ≃ ∆E e,g ≫ k B T , where k B T is the thermal energy, and a strong interband electron-phonon coupling surpasses the thermoelectric limit, provided the optical phonon population is excited in a nanoscale cell -enabling the ensuing local nonequilibrium. Finding and tuning a material with these properties is challenging. In Part II (this issue), we tune the bandgap of graphite within density functional theory through hydrogenation and the application of uniaxial strains. The bandgap is tuned to resonate with its energetic optical phonon modes and calculate the ab initio electron-phonon and phonon-phonon scattering rates. While hydrogenation degrades the strong electron-phonon coupling in graphene such that the figure of merit vanishes, we outline the methodology for a continued material search.

Efficient p-n junction-based thermoelectric generator that can operate at extreme temperature conditions

“…Span et al [11,12] proposed this concept for thin-film PN-TEGs. In a study based on simulation they suggested that a PN-TEG architecture does not only help to solve technological challenges but can also be used to improve the heat to electricity conversion efficiency by the thermal generation of A c c e p t e d M a n u s c r i p t electron-hole pairs within a depletion zone [13,14]. Following these propositions, the role of nonequilibrium charge carriers for thermoelectricity was discussed in Ref.…”

Atomic-Level, Energy-Conversion Heat Transfer

“…This ensures selectively adding to the upconversion rate of the native phonons. As part of the atomic-level heat transfer in energy conversion, the function was examined by reviewing phonon recycling and its conversion to electricity (as in phonovoltaics [10]). Examples commence with phonocatalysis.…”

“…Figure 11(b) signifies the reduced heating, such as the laser crystal operating 12 K lower compared to nonrecycled, requiring 35% less crystal cooling. 12 indicates the phonovoltaic cell is an example of phonoelectricity [10][11][12], harvesting optical phonons equivalent to how a photovoltaic harvests photon. It implies a nonequilibrium (hot) population of optical phonons more energetic than the electronic bandgap (E p,O > DE e;g ) relaxes by generating electron-hole pairs in a diode (a p-n junction).…”

“…This creates an electric potential Du a while inducing recombination as the excited populations (with occupation f e and f h ) relax toward their equilibrium occupations f o e and f o h . When Du a grows sufficiently large, the rate of generation balances with that of recombination [10][11][12].…”

“…Recent advances in computational quantum mechanics allowed for an extension of heat transfer research into thermoelectric materials and electron-phonon coupling. The function of quantum mechanics (ab initio treatments) is established as central to advances in heat transfer research [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”