Search NASA⌕ Search

SEARCH · Search NASA

Results for “phosphides”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

A very low resistance, non-sintered contact system for use on indium phosphide concentrator/shallow junction solar cells

An investigation is made into the possibility of providing low resistance contacts to shallow junction InP solar cells which do not require sintering and which do not cause device degradation even when subjected to extended annealing at elevated temperatures. We show that the addition of In to Au contacts in amounts that exceed the solid solubility limit lowers the as-fabricated (unsintered) contact resistivity (R sub c) to the 10(exp -5) ohm cm(exp 2) range. We next consider the contact system Au/Au2P3 which has been shown to exhibit as-fabricated R sub c values in the 10(exp -6) ohm cm(exp 2) range, but which fails quickly when heated. We show that the substitution of a refractory metal (W, Ta) for Au preserves the low R sub c values while preventing the destructive reactions that would normally take place in this system at high temperatures. We show, finally, that R sub c values in the 10(exp -7) ohm cm(exp 2) range can be achieved without sintering by combining the effects of In or Ga additions to Au contacts with the effects of introducing a thin Au2P3 layer at the metal-InP interface.

Weizer, Victor G.↗
NASA NTRS1991

Minority carrier lifetime in indium phosphide

Transient photoluminescence is used to measure the minority carrier lifetime on n-type and p-type InP wafers. The measurements show that unprocessed InP wafers have very high minority carrier lifetimes. Lifetimes of 200 ns and 700 ns were observed for lightly-doped p- and n-type material respectively. Lifetimes over 5 ns were found in heavily doped n-type material.

Jenkins, Phillip↗
NASA NTRS1991

Influence of the Dislocation Density on the Performance of Heteroepitaxial Indium Phosphide Solar Cells

Calculations are made to study the dependence of heteroepitaxial InP solar-cell efficiency on dislocation density. Effects of surface recombination velocity and cell emitter thickness are considered. Calculated results are compared with the available experimental results on representative InP solar cells. It is shown that heteroepitaxial InP cells with over 20 percent AM0 efficiency could be fabricated if dislocations are reduced to less than 100,000/sq cm.

Jain, R. K.↗
NASA NTRS1992

Three-dimensional numerical modeling of indium phosphide Point-Contact Solar Cells

The Point-Contact Solar Cell (PCSC) geometry has proven very effective for silicon cells. To date, it has not been implemented in III-V materials. In addition, modeling such a geometry is very difficult because of its three-dimensional nature. We have developed a three-dimensional finite element modeling code (FIESTA ROC). In this paper, we present results from a three-dimensional modeling study of InP point-contact solar cells.

Clark, Ralph O.↗
NASA NTRS1995

Naval Research Laboratory's programs in advanced indium phosphide solar cell development

The Naval Research Laboratory has been involved in developing InP solar cell technology since 1988. The purpose of these programs was to produce advanced cells for use in very high radiation environments, either as a result of operating satellites in the Van Allen belts or for very long duration missions in other orbits. Richard Statler was technical representative on the first program, with Spire Corporation as the contractor, which eventually produced several hundred, high efficiency 2 x 2 sq cm single crystal InP cells. The shallow homojunction technology which was developed in this program enabled cells to be made with AMO, one sun efficiencies greater than 19%. Many of these cells have been flown on space experiments, including PASP Plus, which have confirmed the high radiation resistance of InP cells. NRL has also published widely on the radiation response of these cells and also on radiation-induced defect levels detected by DLTS, especially the work of Rob Walters and Scott Messenger. In 1990 NRL began another Navy-sponsored program with Tim Coutts and Mark Wanlass at the National Renewable Energy Laboratory (NREL), to develop a one sun, two terminal space version of the InP-InGaAs tandem junction cell being investigated at NREL for terrestrial applications. These cells were grown on InP substrates. Several cells with AM0, one sun efficiencies greater than 22% were produced. Two 2 x 2 sq cm cells were incorporated on the STRV lA/B solar cell experiment. These were the only two junction, tandem cells on the STRV experiment. The high cost and relative brittleness of InP wafers meant that if InP cell technology were to become a viable space power source, the superior radiation resistance of InP would have to be combined with a cheaper and more robust substrate. The main technical challenge was to overcome the effect of the dislocations produced by the lattice mismatch at the interface of the two materials. Over the last few years, NRL and Steve Wojtczuk at Spire have been developing a single junction InP on Si cell, in an ONR-sponsored SBIR program. Both cell polarities were investigated and the best efficiencies to date (approximately 13% on a 2 x 4 sq cm cell) were achieved with n/p cells. Earlier this year NRL began a program with ASEC to develop a two terminal InP-InGaAs tandem cell on a Ge substrate. RTI and NREL are subcontractors on this program. The results of an ONR-sponsored study of the potential market for InP/Si cells will be discussed. Also the technical status of both the InP/Si and the InP-InGaAs/Ge programs will be given. The technical challenges still remaining will be briefly described.

Summers, Geoffrey P.↗
NASA NTRS1995

Design of a three-layer antireflection coating for high efficiency indium phosphide solar cells using a chemical oxide as first layer

It is well known that the behavior of III-V compound based solar cells is largely controlled by their surface, since the majority of light generated carriers (63% for GaAs and 79% for InP) are created within 0.2 mu m of the surface of the illuminated cell. Consequently, the always observed high surface recombination velocity (SRV) on these cells is a serious limiting factor for their high efficiency performance, especially for those with p-n junction made by either thermal diffusion or ion implantation. A good surface passivation layer, ideally a grown oxide as opposed to a deposited one, will cause a significant reduction in the SRV without adding interface problems, thus improving the performance of III-V compound based solar cells. Another significant benefit to the overall performance of the solar cells can be achieved by a substantial reduction of their large surface optical reflection by the use of a well designed antireflection (AR) coating. In this paper, we demonstrate the effectiveness of using a chemically grown thermally and chemically stable oxide, not only for surface passivation but also as an integral part of a 3-layer AR coating for thermally diffused p+n InP solar cells. A phosphorus-rich interfacial oxide, In(PO3)3, is grown at the surface of the p+ emitter using an etchant based on HNO3, o-H3PO4 and H2O2. This oxide has the unique properties of passivating the surface as well as serving as an efficient antireflective layer yielding a measured record high AMO open-circuit voltage of 890.3 mV on a thermally diffused InP(Cd,S) solar cell. Unlike conventional single layer AR coatings such as ZnS, Sb2O3, SiO or double layer AR coatings such as ZnS/MgF2 deposited by e-beam or resistive evaporation, this oxide preserves the stoichiometry of the InP surface. We show that it is possible to design a three-layer AR coating for a thermally diffused InP solar cell using the In(PO3)3 grown oxide as the first layer and Al2O3 and MgF2 as the second and third layers respectively, so as to yield an overall theoretical reflectance of less than 2%. Since chemical oxides are readily grown on III-V semiconductors materials, the technique of using the grown oxide layer to both passivate the surface as well as serve as the first of a multilayer AR coating should work well for all III-V compound-based solar cells.

Moulot, Jacques↗
NASA NTRS1996

Naval Research Laboratory's programs in advanced indium phosphide solar cell development

The Naval Research Laboratory (NRL) has been involved in the development of solar cells for space applications since the 1960s. It quickly became apparent in this work that radiation damage caused to solar cells by electrons and protons trapped by the earth's magnetic field would seriously degrade the power output of photovoltaic arrays in extended missions. Techniques were therefore developed to harden the cells by shielding them with coverglass, etc. Ultimately, however, there is a limit to such approaches, which is determined by the radiation response of the semiconductor material employed. A desire for high efficiency and radiation resistance led to the development of alternative cell technologies such as GaAs, which has since become the technology of choice for many applications. InP cells are currently the most radiation resistant, high efficiency, planar cells known. NRL first sponsored InP solar cell technology in 1986, when Arizona State University was contracted to grow p/n cells by liquid phase epitaxy. NRL's interest in InP cells was generated by the results presented by Yamaguchi and his co-workers in the early 1980s on the remarkable radiation resistance of cells grown by diffusion of S into Zn doped p-type InP substrates. These cells also had beginning of life (BOL) efficiencies approximately 16%(AM0). Related to the radiation resistance of the cells was the fact that radiation-induced damage could be optically annealed by sunlight. Relatively large quantities of 1 x 2 cm(exp 2) diffused junction cells were made and were used on the MUSES-A and the EXOS-D satellites. These cells were also available in the U.S. through NIMCO, and were studied at NRL and elsewhere. Workers at NASA Lewis became involved in research in InP cells about the same time as NRL.

Summers, Geoffrey P.↗
NASA NTRS1999

Modeling and Real-Time Process Monitoring of Organometallic Chemical Vapor Deposition of III-V Phosphides and Nitrides at Low and High Pressure

The purpose of this paper is to review modeling and real-time monitoring by robust methods of reflectance spectroscopy of organometallic chemical vapor deposition (OMCVD) processes in extreme regimes of pressure. The merits of p-polarized reflectance spectroscopy under the conditions of chemical beam epitaxy (CBE) and of internal transmission spectroscopy and principal angle spectroscopy at high pressure are assessed. In order to extend OMCVD to materials that exhibit large thermal decomposition pressure at their optimum growth temperature we have designed and built a differentially-pressure-controlled (DCP) OMCVD reactor for use at pressures greater than or equal to 6 atm. We also describe a compact hard-shell (CHS) reactor for extending the pressure range to 100 atm. At such very high pressure the decomposition of source vapors occurs in the vapor phase, and is coupled to flow dynamics and transport. Rate constants for homogeneous gas phase reactions can be predicted based on a combination of first principles and semi-empirical calculations. The pressure dependence of unimolecular rate constants is described by RRKM theory, but requires variational and anharmonicity corrections not included in presently available calculations with the exception of ammonia decomposition. Commercial codes that include chemical reactions and transport exist, but do not adequately cover at present the kinetics of heteroepitaxial crystal growth.

Bachmann, K. J.↗
NASA NTRS1995

Design of a Three-Layer Antireflection Coating for High Efficiency Indium Phosphide Solar Cells Using a Chemical Oxide as First Layer

It is well known that the behavior of III-V compound based solar cells is largely controlled by their surface, since the majority of light generated carriers (63% for GaAs and 79% for InP) are created within 0.2 microns of the illuminated surface of the cell. Consequently, the always observed high surface recombination velocity (SRV) on these cells is a serious limiting factor for their high efficiency performance, especially for those with the p-n junction made by either thermal diffusion or ion implantation. A good surface passivation layer, ideally, a grown oxide as opposed to a deposited one, will cause a significant reduction in the SRV without adding interface problems, thus improving the performance of III-V compound based solar cells. Another significant benefit to the overall performance of the solar cells can be achieved by a substantial reduction of their large surface optical reflection by the use of a well designed antireflection (AR) coating. In this paper, we demonstrate the effectiveness of using a chemically grown, thermally and chemically stable oxide, not only for surface passivation but also as an integral part of a 3- layer AR coating for thermally diffused p(+)n InP solar cells. A phosphorus-rich interfacial oxide, In(PO3)3, is grown at the surface of the p(+) emitter using an etchant based on HNO3, o-H3PO4 and H2O2. This oxide has the unique properties of passivating the surface as well as serving as a fairly efficient antireflective layer yielding a measured record high AM0, 25 C, open-circuit voltage of 890.3 mV on a thermally diffused InP(Cd,S) solar cell. Unlike conventional single layer AR coatings such as ZnS, Sb2O3, SiO or double layer AR coatings such as ZnS/MgF2 deposited by e-beam or resistive evaporation, this oxide preserves the stoichiometry of the InP surface. We show that it is possible to design a three-layer AR coating for a thermally diffused InP solar cell using the In(PO3)3 grown oxide as the first layer and Al2O3, MgF2 or ZnS, MgF2 as the second and third layers respectively, so as to yield an overall theoretical reflectance of less than 2%. Since chemical oxides are readily grown on III-V semiconductor materials, the technique of using the grown oxide layer to both passivate the surface as well as serve as the first of a multilayer AR coating, should work well for essentially all III-V compound-based solar cells.

Moulot, Jacques↗
DOE OSTI2021

Elucidating the Location of Cd 2+ in Post-synthetically Treated InP Quantum Dots Using Dynamic Nuclear Polarization 31 P and 113 Cd Solid-State NMR Spectroscopy

Indium phosphide quantum dots (InP QD) are a promising alternative to traditional QD materials that contain toxic heavy elements such as lead and cadmium. However, InP QD obtained from colloidal synthesis are often plagued by poor photoluminescence quantum yields (PL-QYs). In order to improve the PL-QY of InP QD, a number of post-synthetic treatments have been devised. Recently, it has been shown that InP post-synthetically treated with Lewis acid metal divalent cations (M-InP) exhibit enhanced PL-QY; however, the molecular structure and mechanism behind the improved PL-QY are not fully understood. Here, to determine the surface structure of M-InP QD, dynamic nuclear polarization surface-enhanced nuclear magnetic resonance spectroscopy (DNP SENS) experiments were employed on a series of InP magic size clusters treated with Cd ions, InP QD, cadmium phosphide (Cd 3 P 2 ) QD, and Cd-treated InP QD (Cd–InP QD). With the use of DNP SENS, we were able to obtain the 1D 31 P and 113 Cd NMR spectra, 113 Cd{ 31 P} rotational-echo double-resonance (REDOR) NMR spectra, and 31 P{ 113 Cd} dipolar heteronuclear multiple quantum correlation (D-HMQC) sequence. Changes in the phosphide 31 P chemical shifts after Cd treatment provide indirect evidence that some Cd alloys into the sub-surface regions of the particle. DNP-enhanced 113 Cd solid-state NMR spectra suggest that most Cd ions are coordinated by oxygen atoms from either carboxylate ligands or surface phosphate groups. 113 Cd{ 31 P} REDOR and 31 P{ 113 Cd} D-HMQC experiments confirm that a subset of Cd ions are located on the surface of Cd–InP QD and coordinated with phosphate groups.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

High-sensitivity nanoscale chemical imaging with hard x-ray nano-XANES

Resolving chemical species at the nanoscale is of paramount importance to many scientific and technological developments across a broad spectrum of disciplines. Hard x-rays with excellent penetration power and high chemical sensitivity are suitable for speciation of heterogeneous (thick) materials. Here, we report nanoscale chemical speciation by combining scanning nanoprobe and fluorescence-yield x-ray absorption near-edge structure (nano-XANES). First, the resolving power of nano-XANES was demonstrated by mapping Fe(0) and Fe(III) states of a reference sample composed of stainless steel and hematite nanoparticles with 50-nm scanning steps. Nano-XANES was then used to study the trace secondary phases in lithium iron phosphate (LFP) particles. We observed individual Fe-phosphide nanoparticles in pristine LFP, whereas partially (de)lithiated particles showed Fe-phosphide nanonetworks. These findings shed light on the contradictory reports on Fe-phosphide morphology in the literature. Nano-XANES bridges the capability gap of spectromicroscopy methods and provides exciting research opportunities across multiple disciplines.

25 ENERGY STORAGE↗
NASA NTRS1995

Sinterless Fabrication Of Contact Pads On InP Devices

Research has shown that with proper choice of material, low-resistance contact pads deposited on solar cells and other devices by improved technique that does not involve sintering. Research directed at understanding mechanisms involved in contact-sintering process has resulted in identification of special group of materials that includes phosphides of gold, silver, and nickel; specifically, Au(2)P(3), AgP(2), and Ni(3)P. Incorporation of phosphide interlayer substantially reduces resistivity between gold current-carrying layer and indium phosphide substrate. Further research indicated only very thin interlayer of any of these compounds needed to obtain low contact resistance, without subjecting contact to destructive sintering process.

Weizer, Victor G.↗
NASA NTRS1998

Strained quantum well photovoltaic energy converter

An indium phosphide photovoltaic cell is provided where one or more quantum wells are introduced between the conventional p-conductivity and n-conductivity indium phosphide layer. The approach allows the cell to convert the light over a wider range of wavelengths than a conventional single junction cell and in particular convert efficiently transparency losses of the indium phosphide conventional cell. The approach hence may be used to increase the cell current output. A method of fabrication of photovoltaic devices is provided where ternary InAsP and InGaAs alloys are used as well material in the quantum well region and results in an increase of the cell current output.

Freundlich, Alexandre↗
DOE OSTI2024

Bulk‐Heterojunction Electrocatalysts in Confined Geometry Boosting Stable, Acid/Alkaline‐Universal Water Electrolysis

Abstract Alkaline water splitting electrocatalysts have been studied for decades; however, many difficulties remain for commercialization, such as sluggish hydrogen evolution reaction (HER) kinetics and poor catalytic stability. Herein, by mimicking the bulk‐heterojunction morphology of conventional organic solar cells, a uniform 10 nm scale nanocube is reported that consists of subnanometer‐scale heterointerfaces between transition metal phosphides and oxides, which serves as an alkaline water splitting electrocatalyst; showing great performance and stability toward HER and oxygen evolution reaction (OER). Interestingly, the nanocube electrocatalyst reveals acid/alkaline independency from the synergistic effect of electrochemical HER (cobalt phosphide) and thermochemical water dissociation (cobalt oxide). From the spray coating process, nanocube electrocatalyst spreads uniformly on large scale (≈6.6 × 5.6 cm 2 ) and is applied to alkaline water electrolyzers, stably delivering 600 mA cm −2 current for >100 h. The photovoltaic‐electrochemical (PV‐EC) system, including silicon PV cells, achieves 11.5% solar‐to‐hydrogen (STH) efficiency stably for >100 h.

Chemistry↗
DOE OSTI2026

Cs X Si 15 P 21 ( X = Sn or Pb): Polar Noncentrosymmetric Si–P Frameworks Stabilized by Covalent X –P Bonding

Metal silicon phosphides composed of earth-abundant Si and P tend to exhibit semiconducting properties and adopt diverse crystal structures with relatively small additions of structure-directing elements. The potential of silicon phosphide materials in nonlinear optical applications has been hindered by the inability to systematically produce noncentrosymmetric structures with such a flexible framework. Here, in this work, two isostructural compounds with a novel noncentrosymmetric structure were made possible by the inclusion of elements with stereochemically active lone pairs (Sn 2+ and Pb 2+ ). The structures were determined through single-crystal and synchrotron powder X-ray diffraction. Analysis of chemical bonding in real space through the electron localization function revealed stereochemically active Pb 2+ and Sn 2+ species in a trigonal pyramidal coordination with {Pb/Sn}–P bonds. Such covalent bonding between Pb and P is quite uncommon in extended solids and has been reported in a few rare instances. Band structure calculations and linear optical measurements confirm the semiconducting nature of Cs X Si 15 P 21 ( X = Sn or Pb). The synthesis was optimized to yield high-purity polycrystalline samples. The nonlinear optical properties show promising second-harmonic generation (SHG) coefficients from the Kurtz–Perry method. First-principles calculations of the nonlinear optical properties support the experimentally determined SHG values and provide moderate values of birefringence, suggesting Cs X Si 15 P 21 could be phase-matchable and practical nonlinear optical materials in the mid-IR region.

crystal structure↗
DOE OSTI2024

Determining the Effects of Zero-Field Splitting and Magnetic Exchange in Dimeric Europium(II) Complexes

Related BAP [BAP = bis(acyl)phosphide] and Acac (Acac = β-diketonate) molecules perform as robust supports for both lanthanide and actinide metals. Here, a molecular bimetallic Eu 2+ complex was successfully targeted and isolated by employing sodium bis(mesitoyl)phosphide [Na( mes BAP)] in a salt metathesis with EuI 2 , producing [Eu( mes BAP) 2 (et 2 o)] 2 (et 2 o = metal-coordinated diethyl ether). The corresponding Acac-Eu 2+ complex was targeted using mes Acac– (1,3-dimesityl-1,3-propanedione), generating [Eu( mes Acac) 2 (et 2 o)] 2 . Both complexes were characterized by single-crystal X-ray diffraction, UV–vis, IR, and NMR spectroscopies, and variable-temperature magnetic susceptibility. [Eu( mes BAP) 2 (et 2 o)] 2 was persistent under anaerobic, anhydrous conditions, whereas the analogous [Eu( mes Acac) 2 (et 2 o)] 2 showed evidence of decomposition under identical conditions. Finally, variable-temperature magnetic susceptibility and magnetization studies of [Eu( mes BAP) 2 (et 2 o)] 2 and [Eu( mes Acac) 2 (et 2 o)] 2 were performed, resulting in similar magnetic exchange coupling values of J ex = –0.018 and –0.023 cm –1 and axial zero-field-splitting D values of –0.38 and –0.51 cm –1 , respectively.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗