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Thin-Film Selective EmitterDirect conversion of thermal energy into electrical energy using a photovoltaic cell is called thermophotovoltaic energy conversion. One way to make this an efficient process is to have the thermal energy source be an efficient selective emitter of radiation. The emission must be near the band-gap energy of the photovoltaic cell. One possible method to achieve an efficient selective emitter is the use of a thin film of rare-earth oxides. The determination of the efficiency of such an emitter requires analysis of the spectral emittance of the thin film including scattering and reflectance at the vacuum-film and film-substrate interfaces. Emitter efficiencies (power emitted in emission band/total emitted power) in the range 0.35-0.7 are predicted. There is an optimum optical depth to obtain maximum efficiency. High emitter efficiencies are attained only for low (less than 0.05) substrate emittance values, both with and without scattering. The low substrate emittance required for high efficiency limits the choice of substrate materials to highly reflective metals or high-transmission materials such as sapphire.
Document ID
19980025528
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Chubb, Donald L.
(NASA Lewis Research Center Cleveland, OH United States)
Lowe, Roland A.
(Cleveland State Univ. Cleveland, OH United States)
Date Acquired
September 6, 2013
Publication Date
November 1, 1993
Publication Information
Publication: Journal of Applied Physics
Publisher: American Inst. of Physics
Volume: 74
Issue: 9
ISSN: 0021-8979
Subject Category
Electronics And Electrical Engineering
Report/Patent Number
NAS 1.15:113079
NASA-TM-113079
E-7639
Distribution Limits
Public
Copyright
Public Use Permitted.
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