title: A hot-electron thermophotonic solar cell demonstrated by thermal up-conversion of sub-bandgap photons.
abstract: The direct conversion of solar energy to electricity can be broadly separated into two main categories: photovoltaics and thermal photovoltaics, where the former utilizes gradients in electrical potential and the latter thermal gradients. Conventional thermal photovoltaics has a high theoretical efficiency limit (84%) but in practice cannot be easily miniaturized and is limited by the engineering challenges of sustaining large (>1,000 K) temperature gradients. Here we show a hot-carrier-based thermophotonic solar cell, which combines the compact nature of photovoltaic devices with the potential to reach the high-efficiency regime of thermal photovoltaics. In the device, a thermal gradient of 500 K is established by hot electrons, under Stokes illumination, rather than by raising the temperature of the material itself. Under anti-Stokes (sub-bandgap) illumination we observe a thermal gradient of ∼20 K, which is maintained by steady-state Auger heating of carriers and corresponds to a internal thermal up-conversion efficiency of 30% between the collector and solar cell.
authors.affiliation: Research Centre for Advanced Science and Technology (RCAST), The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8504, Japan.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Farrell
authors.affiliation: Research Centre for Advanced Science and Technology (RCAST), The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8504, Japan.
authors.forename: Hassanet
authors.initials: H
authors.lastname: Sodabanlu
authors.affiliation: Research Centre for Advanced Science and Technology (RCAST), The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8504, Japan.
authors.forename: Yunpeng
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Electrical Engineering and Information Systems, Graduate School of Engineering, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Sugiyama
authors.affiliation: Research Centre for Advanced Science and Technology (RCAST), The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8504, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Okada