摘要:

GaInSb and GaSb layers have been grown on GaSb and GaAs substrates using metalorganic vapor phase epitaxy (MOVPE) with trimethylgallium, trimethylindium, and trimethylantimony as the sources. As grown layers werep‐type with the carrier concentration in the mid‐1016cm−3range.N‐type layers were grown using diethyltellurium as the Te source. Incorporation of Te in high concentration showed compensation and secondary ion mass spectrometry (SIMS) result showed that only 2.5% of Te are active when 2×1019cm−3of Te was incorporated. The carrier concentration measured inn‐type samples increased as the temperature is lowered. This is explained by the presence of second band close to the conduction band minima. Silane, which is a commonn‐type dopant in GaAs and other III–V systems, is shown to behave likep‐type in GaInSb‐.P‐njunction structures have been grown on GaSb substrates to fabricate TPV cells. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49703

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The ternary semiconductor InxGa1−xAs has been a key component of current thermophotovoltaic energy converters. These studies indicate that the bandgap of the epitaxial films, that are lattice‐matched to InP, show varying degrees of ordering of the metal sublattice depending upon growth temperature. The bandgap of partially ordered films is lowered by as much as 75 meV. The transport of carriers in ordered films is dominated by domain trapping. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49704

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The paper reviews the effect of the energy bandgap of TPV converters on their conversion efficiency. Several sources are analyzed, monochromatic, narrow band (selective emitters) and broad band (blackbodies). We find that at low bandgaps, conversion efficiency falls off. The conclusion drawn should help in estimates in all cases of practical efficiencies to be used in TPV system analysis. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49705

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report on the development ofp‐on‐nGaxIn(1−x)As thermophotovoltaic devices. For Ga0.47In0.53As cells, lattice‐matched to InP and having a bandgap of 0.73 eV, then‐on‐pconfiguration gives better results than thep‐on‐nconfiguration. However, for Ga0.32In0.68As cells, grown on InP and having a bandgap of 0.58 eV, thep‐on‐npolarity has superior performance for cells with similar step‐graded buffer layers. The improvement in thep‐on‐ndevices is due to reduced dark currents and increased open circuit voltages (Voc). Optimized back surface field layers produce these effects. Because of the absorption of long wavelength light in the base region of low bandgap materials, a high quality back surface acts as a minority carrier mirror and reduces recombination in buffer layers. We have been able, so far, to get more effective back surface field layers with thep‐on‐nconfiguration. While then‐on‐ppolarity may offer the advantage of lower cell emitter sheet resistivity, thep‐on‐ndevice offers lower free carrier absorption of long wavelength radiation, better spectral control of incoming radiation, and improved large scale manufacturing ability. Results for several differentp‐on‐ncell structures for the 0.73 eV and 0.58 eV GaxIn(1−x)As compositions will be reported. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49706

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

One of the key priorities in the development of Thermophotovoltaic power technology is a highly efficient heat‐source/emitter system that is robust and stable. This paper describes a tightly coupled burner/selective emitter combination that integrates two novel concepts that are now under development: A fluidized bed emitter that consists of hollow, submillimeter spheres as the sources of radiant energy and a non‐premixed, self regulating burner. The rationale behind the proposed system is to combine the unique intrinsic features of both concepts to provide the TPV community with an enabling technology. The fluidized bed provides excellent heat transfer, temperature uniformity, high radiant power density, reduced substrate and combustion background, robustness, thermal shock resistance, minimal contamination, and long operational life. The paper discusses a fluidized bed system that consists of selectively emitting, hollow Ho‐YAG spheres with 500 micron diameter and 10–100 micron shell thickness operating at 1500 K. Key issues related to heat transfer and radiation transport in the fluidized bed are analyzed. The collective emitter efficiency and power density of a fluidized bed are discussed. The non‐premixed burner achieves very high temperatures, has a low emission in toxic byproducts, provides self regulating stability, eliminates flashback hazards, and is operable with hydrogen. The paper concludes with a description of a complete fluidized bed TPV system including an elliptic/parabolic transfer optics and a photovoltaic cavity converter that boosts the flux density received by the photovoltaic cells. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49714

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

An improved ceramic spine disc burner/emitter for use in a thermophotovoltaic (TPV) generator is described. A columnar infrared (IR) emitter consisting of a stack of silicon carbide (SiC) spine discs provides for both high conductance for the combustion gases and efficient heat transfer from the hot combustion gases to the emitter. Herein, we describe the design, fabrication, and testing of this SiC burner as well as the characterization of the IR spectrum it emits. We note that when the SiC column is surrounded with fused silica heat shields, these heat shields suppress the emitted power beyond 4 microns. Thus, a TPV generator using GaSb photovoltaic cells covered by simple dielectric filters can convert over 30% of the emitted IR radiation to DC electric power. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49707

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have demonstrated a new class of material which appear to provide significant advantages as TPV emitters, including selective emission, high power density by virtue of operation at very high temperature, stability in air, appreciable thermal shock resistance, and the ability to be produced in desired shapes. These materials also afford the possibility of tuning the characteristic emission wavelength to various bands as may be desired, and the possibility of being powered by any one of a variety of power sources, including gas flames and concentrated solar energy. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49708

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The present Jet Propulsion Laboratory (JPL) characterization test method for a single thermophotovoltaic (TPV) cell is to illuminate the cell with black body emission. However, this method is inadequate for the performance testing of a string or an array of cells. This is simply because the black body aperture is too small to supply sufficient illumination for much more than a single, small cell. Alternative light sources for TPV string or array testing would be to use a large area gray body, a diffused high power laser, a high power lamp array, or the Large Area Pulsed Solar Simulator (LAPSS). These methods are analyzed and compared. Conclusions are drawn concerning the needs and methods of TPV string and array testing. The large area gray body source was found to need more development toward larger sizes. The color temperature of this source is limited and a cooling system is required for the test devices. The diffused high power laser source was found to be expensive and power limited. This source would require a special optical system to achieve uniform illumination and also requires a cooling system for the test devices. The high power lamp array source was found to need some development and it would require cooling systems for the lamps and the test devices. The LAPSS was found to be a feasible light source. It required very little development funds and did not heat the test article. In the near term, it was decided to use the LAPSS as the TPV light source. A preliminary technique using the LAPSS with an infrared bandpass filter was developed for high power, 8 watts per square centimeter, TPV testing purposes. Initial results indicate that this system is applicable to single cell, string, and array testing of TPV cells because of its high emission power density and well matched emission spectrum. Tests and analyses were performed to establish test plane intensity and uniformity versus test device distance from the lamps. In addition, tests and analyses were performed to determine the spectral transmission characteristics of various infrared bandpass filter combinations. The LAPSS, with the infrared bandpass filter, is now operational at JPL for TPV cell, string, and array testing. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49709

出版商:AIP    

年代:1996

数据来源: AIP