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Results for “PHOTOVOLTAIC CONVERSION”

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.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Nonradiative Recombination Dominates Voltage Losses in Cu(In,Ga)Se 2 Solar Cells Fabricated using Different Methods

Voltage losses reduce the photovoltaic conversion efficiency of thin‐film solar cells and are a primary efficiency limitation in Cu(In,Ga)Se 2 . Herein, voltage loss analysis of Cu(In,Ga)Se 2 solar cells fabricated at three institutions with variation in process, bandgap, absorber structure, postdeposition treatment (PDT), and efficiency is presented. Nonradiative voltage losses due to Shockley–Read–Hall charge carrier recombination dominate and constitute >75% of the total compared to <25% from radiative voltage losses. The radiative voltage loss results from nonideal absorption and carriers in band tails that stem from local composition‐driven potential fluctuations. It is shown that significant bulk lifetime improvements are achieved for all alkali PDT processed absorbers, chiefly associated with reductions in nonradiative recombination. Primary voltage loss contributions (radiative and nonradiative) change little across fabrication processes, but variation in submechanisms (bulk lifetime, net acceptor concentration, and interface recombination) differentiate nonradiative loss pathways in this series of solar cells.

14 SOLAR ENERGY↗
DOE OSTI2023

Improving the barrier properties of tin oxide in metal halide perovskite solar cells using ozone to enhance nucleation

Here we investigate tin oxide growth on fullerene (C 60 ) by atomic layer deposition (ALD) for C 60 /oxide bilayer electron selective contacts in P-I-N metal halide perovskite (MHP) solar cells. An in situ ozone functionalization step is incorporated in an ALD SnO x process to suppress sub-surface growth, leading to improved internal barrier performance of ALD SnO x thin films grown on fullerene surfaces. We show that this approach decreases the water-vapor transmission rate of C 60 /ALD SnO x barriers by an order of magnitude and improves the barrier properties against gas, solvent, and halide migration. Furthermore, ozone-treated SnO x barriers can narrow photovoltaic performance distribution without compromising efficiency. We demonstrate the universality of this approach in wide-, intermediate-, and low-gap perovskite systems and further show that enhancement of the ALD barrier layer is critical toward improving the yield of all-perovskite tandem solar cells. Two-terminal all-perovskite tandem solar cells incorporating ozone nucleation are reported at over 24% photovoltaic conversion efficiency.

14 SOLAR ENERGY↗
NASA NTRS1975

Applied research on 2-6 compound materials for heterojunction solar cells

Several II-VI heterojunctions show promise for photovoltaic conversion of solar energy. The three of greatest interest are p-CdTe/n-CdS, p-CdTe/n-ZnSe, and p-ZnTe/n-CdSe. Several p-CdTe/n-CdS heterojunction cells have been prepared by close spaced transport deposition of p-CdTe on single crystal n-CdS, and by two source vacuum evaporation of n-CdS on single crystal p-CdTe. Both types of cells, in an experimental stage, are quite comparable, exhibiting values of quantum efficiency between 0.5 and 0.9, open circuit voltages between 0.50 and 0.66 V, fill factors between 0.4 and 0.6, and solar efficiencies up to 4 percent. Cells of p-ZnTe/n-CdSe have also been made by close spaced vapor transport deposition of n-CdSe on single crystal p-ZnTe.

Bube, R. H.↗
NASA NTRS1976

LSSA (Low-cost Silicon Solar Array) project

The Photovoltaic Conversion Program was established to find methods of economically generating enough electrical power to meet future requirements. Activities and progress in the following areas are discussed: silicon-refinement processes; silicon-sheet-growth techniques; encapsulants; manufacturing of off-the-shelf solar arrays; and procurement of semistandardized solar arrays.

Source record↗
NASA NTRS1977

The economic viability of pursuing a space power system concept

The development of a space power system requires no fundamental technological breakthroughs. There are, however, uncertainties regarding the degree to which necessary developments can be achieved or exceeded. An analysis is conducted concerning the implementation of a 5000 MW space-based solar power system based on photovoltaic conversion of solar energy to electrical energy. The solar array is about 13 km long and 5 km wide. Placed in geosynchronous orbit, it provides power to the earth for 30 years. Attention is given to the economic feasibility of a space power system, a risk analysis for space power systems, and the use of the presented methodology for comparing alternative technology development programs.

Hazelrigg, G. A., Jr.↗
NASA NTRS1976

Photovoltaic test and demonstration project

The considered project consists of three subprojects related to applications, device performance and diagnostics, and endurance testing. The objectives of the applications subproject include the determination of the operating characteristics for a variety of photovoltaic conversion systems. A system test facility is being constructed in this connection and a prototype residence experiment is to be conducted. Market demand for solar cells is to be stimulated by demonstrating suitability of solar cells for specific near-term applications. Activities conducted in connection with device performance studies and diagnostics are also discussed along with developments in the area of endurance testing.

Forestieri, A. F.↗
NASA NTRS1978

Photovoltaic research and development status

The goals of the Photovoltaic R&D Program are to develop thin film semiconductor and novel photovoltaic conversion concepts, and to demonstrate the feasibility of producing these cells for a price of $100 - $300 per peak electric output (in 1975) by FY1985. The approaches that are used to determine which research should be funded are formal solicitations, an innovative concepts program which will be launched in FY79, and the review of unsolicited proposals.

Feucht, D. L.↗
NASA NTRS1983

Analysis of the reflective multibandgap solar cell concept

A new and unique approach to improving photovoltaic conversion efficiency, the reflective multiband gap solar cell concept, was examined. This concept uses back surface reflectors and light trapping with several physically separated cells of different bandgaps to make more effective use of energy from different portions of the solar spectrum. Preliminary tests performed under General Dynamics Independent Research and Development (IRAD) funding have demonstrated the capability for achieving in excess of 20% conversion efficiency with aluminum gallium arsenide and silicon. This study analyzed the ultimate potential for high conversion efficiency with 2, 3, 4, and 5 different bandgap materials, determined the appropriate bandgaps needed to achieve this optimized efficiency, and identified potential problems or constraints. The analysis indicated that an improvement in efficiency of better than 40% could be attained in this multibandgap approach, compared to a single bandgap converter under the same assumptions. Increased absorption loss on the back surface reflector was found to incur a minimal penalty on efficiency for two and three bandgap systems. Current models for bulk absorption losses in 3-5 materials were found to be inadequate for explaining laboratory observed transmission losses. Recommendations included the continued development of high bandgap back surface reflector cells and basic research on semiconductor absorption mechanisms.

Stern, T. G.↗
NASA NTRS1985

Top-Coating Silicon Onto Ceramic

Polycrystalline silicon for solar cells produced at low cost. Molten silicon poured from quartz trough onto moving carbon-coated ceramic substrate. Doctor blade spreads liquid silicon evenly over substrate. Molten material solidifies to form sheet of polycrystalline silicon having photovoltaic conversion efficiency greater than 10 percent. Method produces 100-um-thick silicon coatings at speed 0.15 centimeter per second.

Heaps, J. D.↗
NASA NTRS1984

Research directions and progress in SERI advanced high efficiency concepts program

Novel solar cell designs and materials with the objective of achieving the maximum attainable photovoltaic conversion efficiencies are researched. Laboratory demonstrations of solar cells of greater than 30% efficiency under concentrated sunlight and thin film solar cells with one sun efficiencies of 17 to 20% are sought. These demonstrations are necessary intermediate steps towards the realization of very high efficiency, multi-bandgap, thin-film solar cells. Conversion efficiencies above 30% could be achieved by a cascade multijunction cell consisting of a high bandgap (1.7 eV) cell coupled optically and electrically on top of a lower bandgap (1.1 eV) cell. Recent improvements in peak currents of this interconnect are quite promising. However, this cell structure poses difficult problems for materials fabrication as a result of the combined requirements of choice of bandgaps, low defect density material, and high doping densities. Recent improvements in the quality of materials and newly proposed cell structures which may simplify fabrication are significant steps in the development of the multijunction concentrator solar cell.

Benner, J. P.↗
NASA NTRS1987

Solar cells in bulk InP using an open tube diffusion process

A simple open tube diffusion technique for the fabrication of n+p junction solar cells is described. Large area (greater than 0.25 square cm) solar cells have been made by this process with a photovoltaic conversion efficiency of 15.2 percent under simulated AMO illumination. An ideality factor is 1.04 and a saturation current density of 9.6 times 10 to the minus 16th power A/square cm have been observed for these cells. These are the lowest (best) values reported to date for diffused structures in bulk InP.

Parat, K. K.↗
NASA NTRS1989

Roughening Surfaces Of Solar Cells

Proposed treatment involving bombardment by ions gives silicon solar cells rough surfaces and increases amount of light absorbed by cells. First step of treatment, wafer of single-crystal silicon held at temperature of 70 degree C or higher while bombarded with argon or hydrogen ions at kinetic energies between 100 and 2,000 eV. This high dose produces damaged layer on surface, consisting of outer polycrystalline sublayer and underlying sublayer containing extended defects. Bombarded wafer then etched chemically. Photovoltaic conversion efficiency increases with number of reflections at surface of silicon cell because large part of light absorbed at each reflection. Deeply textured surface provides opportunities for multiple reflections.

Singh, Ranbir↗
NASA NTRS1989

Encapsulated diffusion of sulphur into InP

This talk outlines a simple process for the fabrication of n(+)-p solar cells in indium phosphide. Large area cells (greater than 0.25 sq cm) have been made by this process, with a photovoltaic conversion efficiency of 15.21 percent under AM0 conditions of illumination. An ideality factor of 1.1 and a saturation current density of 8 x 10 to the minus 15th power A/sq cm have been observed for these cells. The technique for cell fabrication involves the diffusion of sulfur into InP by an open tube process, and gives highly reproducible results from run to run. A vacuum-deposited layer of gallium sulphide (Ga2S3) was used as the source for sulfur diffusion, with a chemically vapor deposited SiO2 cap layer to prevent decomposition of the InP surface during heat treatment. Diffusions were carried out in a flowing nitrogen ambient at 585 to 708 C, and characterized by their surface carrier concentration and the diffusion constant. The diffusion profile for sulfur in InP is estimated to be of the complementary error function type. The activation energy of the diffusion was estimated to be 1.94 eV. The technique described here is ideally suited for the fabrication of shallow n(+)-p junctions in InP, and has been used for space-borne solar cells.

Parat, K. K.↗
NASA NTRS1995

Pulsed laser illumination of photovoltaic cells

In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic receivers to provide remote power. Both the radio-frequency (RF) and induction FEL produce pulsed rather than continuous output. In this work we investigate cell response to pulsed laser light which simulates the RF FEL format. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced compared to constant illumination at the same wavelength. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments indicates that the RF FEL pulse format yields more efficient photovoltaic conversion than does an induction FEL format.

Yater, Jane A.↗
NASA NTRS1994

Pulsed laser illumination of photovoltaic cells

In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic array receivers to provide remote power. Both the radio-frequency (RF) and induction FEL provide FEL produce pulsed rather than continuous output. In this work we investigate cell response to pulsed laser light which simulates the RF FEL format. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced compared to constant illumination at the same wavelength. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments indicates that the RF FEL pulse format yields more efficient photovoltaic conversion than does an induction FEL pulse format.

Yater, Jane A.↗
NASA NTRS1994

Pulsed Laser Illumination of Photovoltaic Cells

In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic array receivers to provide remote power. The induction FEL and the radio-frequency (RF) FEL both produce pulsed rather than continuous output. In this work, we investigate cell response to pulsed laser light which simulates the RF FEL format, producing 50 ps pulses at a frequency of 78 MHz. A variety of Si, GaAs, CaSb and CdInSe2 (CIS) solar cells are tested at average incident powers between 4 mW/sq cm and 425 mW/sq cm. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced by using a pulsed laser source compared to constant illumination at the same wavelength. Because the pulse separation is less than or approximately equal to the minority carrier lifetime, the illumination conditions are effectively those of a continuous wave laser. The time dependence of the voltage and current response of the cells are also measured using a sampling oscilloscope equipped with a high frequency voltage probe and current transformer. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments shows that the RF FEL pulse format yields much more efficient photovoltaic conversion of light than does an induction FEL pulse format.

Yater, Jane A.↗
DOE OSTI2020

Solar power system using hybrid trough and photovoltaic two-stage light concentration

A solar power method is provided using two-stage light concentration to drive concentrating photovoltaic conversion in conjunction with thermal collection. The method concentrates light rays received in a plurality of transverse planes towards a primary linear focus in an axial plane, which is orthogonal to the transverse planes. T band wavelengths of light are transmitted to the primary linear focus. R band wavelengths of light are reflected towards a secondary linear focus in the axial plane, which is parallel to the primary linear focus. The light received at the primary linear focus is translated into thermal energy. The light received at the secondary linear focus is focused by optical elements along a plurality of tertiary linear foci, which are orthogonal to the axial plane. The focused light in each tertiary primary focus is focused into a plurality of receiving areas, and translated into electrical energy.

14 SOLAR ENERGY↗