Loss mechanisms and back surface field effect in photon enhanced thermionic emission converters

Gideon Segev, Yossi Rosenwaks, Abraham Kribus*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

Photon Enhanced Thermionic Emission (PETE) solar converters are based on emission of energetic electrons from a semiconductor cathode that is illuminated and heated with solar radiation. By using a semiconductor cathode, photo generated electrons enable high electron emission at temperatures much lower than the common range for thermionic emitters. Simple models show that PETE conversion can theoretically reach high efficiency, for example, above 40% at concentration of 1000 suns. In this work, we present a detailed one-dimensional model of PETE conversion, accounting for recombination mechanisms, surface effects, and spatial distribution of potential and carrier concentration. As in the previous PETE models, negative space charge effects, photon recycling, and temperature gradients are not considered. The conversion efficiency was calculated for Si and GaAs based cathodes under a wide range of operating conditions. The calculated efficiencies are lower than predictions of previous zero-dimensional models. We analyze the loss mechanisms and show that electron recombination at the cathode contact is a significant loss. An electron-blocking junction at the cathode back contact is therefore essential for achieving high efficiency. The predicted efficiencies for Si and GaAs cathodes with homo-junction back surface field layers are both around 31%, but with more favorable assumptions on the contact structure, it may be near 40%. The analysis leads to important conclusions regarding the selection of cathode material and back surface junction configuration.

Original languageEnglish
Article number044505
JournalJournal of Applied Physics
Volume114
Issue number4
DOIs
StatePublished - 28 Jul 2013

Funding

FundersFunder number
Israel Ministry of Energy and Water
Ministry of Science and Technology, Israel

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