Plasmon-enhanced internal photoemission for photovoltaics: Theoretical efficiency limits
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(a) Geometry of a plasmon-enhanced internal photoemission solar cell. (b) Excitation of electrons in the metal from occupied energy levels in the conduction band (shaded gray) to unoccupied levels above the Fermi energy . Left axis: parabolic density of states (DOS) in the conduction band. Right axis: distribution of hot electron energies given by the EDJDOS. (c) Energy diagram of the Schottky junction at the metal-semiconductor interface (shown for an n-type semiconductor). Hot electrons with energy can be emitted over the barrier into the semiconductor; those without enough energy are reflected back into the metal.
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(a) Distribution of hot electron energies (EDJDOS) in Ag for incident photons of energy . Zero on the horizontal axis is . Shaded areas indicate electrons with sufficient energy to cross a Schottky barrier of height . (b) Electron emission efficiency () dependence on photon energy for the same parameters in (a). (c) Maximum power conversion efficiency as a function of under solar illumination, calculated for the EDJDOS shown in (a) (solid) and for a uniform electron energy distribution (dashed). (d)-(f) show the same data as (a)-(c), but calculated for a narrow DOS distribution close to the Fermi level, and with .
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