Optical refrigeration for ultra-efficient photovoltaics

Assaf Manor; Leopoldo L. Martin; Carmel Rotschild

doi:10.1117/12.2076275

10 March 2015 Optical refrigeration for ultra-efficient photovoltaics

Assaf Manor, Leopoldo L. Martin, Carmel Rotschild

Proceedings Volume 9380, Laser Refrigeration of Solids VIII; 93800L (2015) https://doi.org/10.1117/12.2076275
Event: SPIE OPTO, 2015, San Francisco, California, United States

Abstract

The Shockley-Queisser (SQ) efficiency limit for single-junction photovoltaic cell (PV) is to a great extent due to inherent heat dissipation accompanying the quantum process of electro-chemical potential generation. Concepts such as solar thermophotovoltaics^1,2,3 (STPV) and thermo-photonics⁴ aim to harness this dissipated heat, claiming very high theoretical limit. In practice, none of these concepts have been experimentally proven to overcome the SQ limit, mainly due to the very high operating temperatures, which significantly challenge electro-optical devices. In contrast to the above concepts for harnessing thermal emission at thermal equilibrium, Photoluminescence (PL) is a fundamental light-matter interaction under non-thermal equilibrium, which conventionally involves the absorption of energetic photon, thermalization and the emission of a red-shifted photon. Conversely, in optical-refrigeration the absorption of low energy photon is followed by endothermic-PL of energetic photon^5,6. Both aspects were mainly studied where thermal population is far weaker than photonic excitation, obscuring the generalization of PL and thermal emissions. Here we experimentally study endothermic-PL at high temperatures⁷. In accordance with theory, we show how PL photon rate is conserved with temperature increase, while each photon is blue shifted. Further rise in temperature leads to an abrupt transition to thermal emission where the photon rate increases sharply. We also show how endothermic-PL generates orders of magnitude more energetic photons than thermal emission at similar temperatures. Relying on these observations, we propose and study thermally enhanced PL (TEPL) for highly efficient solar-energy conversion. Here, solar radiation is absorbed by a low-bandgap PL material. The dissipated heat is emitted by endothermic PL, and harvested by a higher-bandgap photovoltaic cell. While such device operates at much lower temperatures than STPV, the theoretical efficiencies approach 70%, bringing its realization into reach.

Citation Download Citation

Assaf Manor, Leopoldo L. Martin, and Carmel Rotschild "Optical refrigeration for ultra-efficient photovoltaics", Proc. SPIE 9380, Laser Refrigeration of Solids VIII, 93800L (10 March 2015); https://doi.org/10.1117/12.2076275

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