Limiting efficiencies of solar energy conversion and photo-detection via internal emission of hot electrons and hot holes in gold

Abstract

We evaluate the limiting efficiency of full and partial solar spectrum harvesting via the process of internal photoemission in Au-semiconductor Schottky junctions. Our results based on the ab initio calculations of the electron density of states (e-DOS) reveal that the limiting efficiency of the full-spectrum Au converter based on hot electron injection is below 4%. This value is even lower than previously established limit based on the parabolic approximation of the Au electron energy bands. However, we predict limiting efficiency exceeding 10% for the hot holes collection through the Schottky junction between Au and p-type semiconductor. Furthermore, we demonstrate that such converters have more potential if used as a part of the hybrid system for harvesting high-and low-energy photons of the solar spectrum.

Harvesting the loss: surface plasmon-based hot electron photodetection

“…Hot carriers are primarily generated with momentum parallel to the external field [31], which is generally parallel with the semiconductor interface in the case of an antenna, resulting in poor injection. Moreover, hot electron generation is also dependent on the plasmonic material employed [32,72,[76][77][78]. Several groups have explored the effects of the electronic structure of the metal on the generated carrier distributions [32,76] ( Figure 1F), and it has been shown that, in the interband transition regime, the electronic band structure of the metal plays an important role in determining both the energy and the momentum distribution of the generated hot carriers [32].…”

Roadmap on optical energy conversion

“…To date, the series multijunction cell is the only proven solution to the spectral issue [see sections 11,13]. As also described elsewhere in this roadmap, there are several alternative concepts proposed to deal with the problem, from carrier multiplication to hot electron extraction [see sections 5,13] to parallel multijunction (as in a prism) [see sections 11,13] to thermal PV [see sections [15][16][17][18][19][20]. Likewise for the optical absorber thickness issue, various light-trapping innovations are being conceived and imple-mented to enable high absorption in ultrathin media.…”

“…Proposals of photovoltaic up conversion and down conversion notwithstanding [see sections [13][14][15][16][17][18], current proposals are far below the required performance. Hence, in the foreseeable future, the focus will likely be on the types of nonimaging and aplanatic optics, gradient-index optics, and micromodularity (permitting optics precluded by common large-absorber collectors) that not only can raise solar conversion efficiency, but can render them more practical and amenable to large-volume production.…”

“…the controversy about the thermodynamic second law violation in optical refrigeration (i.e., anti-Stokes fluorescent cooling) 18,19 . It is also at the core of efficiency limits of the photon energy conversion 20 .…”

“…2b). Many opportunities still exist not only for material designers [see sections 3,[5][6][7][8][9][10]14] but also for optical scientists and engineers to reach and overcome the efficiency limits [see sections [2][3][4][9][10][11][12][13][14][15][16][17][18][19]. Novel optical concepts and schemes for light concentration, photon trapping, optical spectrum splitting, and material emittance modification offer new insights and yield new technological solutions for solar and thermal energy harvesting.…”