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Results for “PHOTOVOLTAIC EFFECT”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Heat treatment effects in Cu2S-CdS heterojunction photovoltaic cells

The dependence of the short-circuit current on photon energy, temperature, and the state of optical degradation (or enhancement) is determined in a study of the photovoltaic properties of Cu2S-CdS single-crystal heterojunctions. A coherent formulation is proposed for the relationship between enhancement and optical degradation and for their effects on the transport of a short-circuit photoexcited current and dark forward-bias current in a photovoltaic cell. Optical degradation in a Cu2S-CdS cell is shown to be identical to the optical degradation of lifetime in a homogeneous CdS:Cd:Cu crystal.

Fahrenbruch, A. L.↗
DOE OSTI2022

Temperature-Dependent Carrier Extraction and the Effects of Excitons on Emission and Photovoltaic Performance in Cs0.05FA0.79MA0.16Pb(I0.83Br0.17)3 Solar Cells

The photovoltaic parameters of triple cation perovskite [Cs0.05FA0.79MA0.16Pb(I0.83Br0.17)3] solar cells are investigated focusing on the electro-optical properties and differences in performance at low and high temperatures. The signature of a parasitic barrier to carrier extraction is observed at low temperatures, which results in a loss of performance at T < 200 K. Intensity-dependent measurements indicate extraction across this parasitic interface is limited by a combination of the exciton binding energy and thermionic emission. However, the photovoltaic performance of the device is recovered at low intensity - where the photocarrier generation rate threshold is lower than the thermionic extraction rate. Loss of solar cell performance is also observed to be strongly correlated to an increase in photoluminescence intensity, indicating inhibited carrier extraction results in strong radiative recombination and that these systems do not appear to be limited by significant thermally activated non-radiative processes. Evidence of limited carrier extraction due to excitonic effects is also observed with a strong anti-correlation in photoluminescence and carrier extraction observed at lower temperatures.

barrier↗
NASA NTRS1973

Heat treatment effects in Cu2S-CdS heterojunction photovoltaic cells

The optical and electronic properties of single crystal Cu2S-CdS photovoltaic cells were investigated. In these cells trapped charge near the interface which is manifested by a persistent increase in junction capacitance (the photocapacitance) plays a significant role in determining the carrier transport properties. It was found that the severe degradation in short-circuit current observed in heat-treated cells can be separated into two components: (1) a relatively small thermal component occurring on heat-treatment in the dark, and (2) a much larger degradation caused by exposure to light at room temperature. By a short additional heat-treatment above approximately 100 C the cell can be completely restored to its condition before the optically caused degradation with no effect on the depletion layer width.

Fahrenbruch, A. L.↗
NASA NTRS1989

Review of the environmental effects of the Space Station Freedom photovoltaic power module

An overview is provided of the environment in the low Earth orbit (LEO), the interaction of this environment with the Photovoltaic (PV) Power system of the Space Station Freedom is reviewed, and the environmental programs are described that are designed to investigate the interactions of the LEO environment with the photovoltaic power system. Such programs will support and impact the design of the subsystems of the PV module in order to survive the design lifetime in the LEO natural and induced environment.

Nahra, Henry K.↗
NASA NTRS1989

Review of the environmental effects on the Space Station Freedom photovoltaic power module

An overview is provided of the environment in the low earth orbit (LEO), the interaction of this environment with the photovoltaic (PV) power system of the Space Station Freedom is reviewed, and the environmental programs are described that are designed to investigate the interaction of the LEO environment with the photovoltaic power system. Such programs will support and impact the design of the subsystems of the PV module in order to survive the design lifetime in the LEO natural and induced environment.

Nahra, Henry K.↗
NASA NTRS1995

ACTS for distance education in developing countries

The need for electrical energy supply in the rural communities of developing countries has been well documented. Equally well known is the potential for photovoltaic in cost effectively meeting this need. A major impediment to fulfilling the need is the lack of indigenous personnel with a knowledgeof photovoltaic systems, and the associated infrastructure required to implement project. Various delivery schemes for providing the needed training to developing countries personnel have been investigated. Various train methods and programs that have been employed to remedy the problem have had significant drawbacks in terms of cost, consistency, impact, reach, and sustainability. The hypothesis to be tested in this project posits that satellite-based distance education using ACTS technologies can overcome these impediments. The purpose of the project is to investigate the applicability of the ACTS satellite in providing distance education in photovoltaic systems to developing countries and rural communities. An evaluation of the cost effectiveness of using ACTS unique technologies to overcome identified problems shall be done. The limitations of ACTS in surmounting distance education problems in developing countries shall be investigated. This project will, furthermore, provide training to Savannah State College faculty in photovoltaic (PV) systems and in distance education configurations and models. It will also produce training materials adequate for use in PV training programs via distance education. Savannah State College will, as a consequence become well equipped to play a leading role in the training of minority populations in photovoltaic systems and other renewables through its Center for Advanced Water Technology and Energy Systems. This communication provides the project outline including the specific issues that will be investigated during the project. Also presented i the project design which covers the participations of the various components of a network of institutions that is formed for optimal project execution. The expected results and project output, including plans for potential leverages and linkages to be derived, are also discussed. Finally, we point out possible extensions from this project and other related projects that could be initiated based on the experiences gained from the project.

Kalu, A↗
NASA NTRS1984

Synthesis of major economic studies of residential photovoltaics

Six studies that analyze the cost effectiveness of grid connected residential photovoltaic systems are reviewed. These six studies were selected based on two criteria. First, the reports share common emphases on developing photovoltaic systems with certain engineering design goals in mind, and on performing economic analyses to assess the long term economic potential of the system design. The economic analyses presented are performed from the consumer's perspective.

Source record↗
NASA NTRS1978

Simulated hail impact testing of photovoltaic solar panels

Techniques used to simulate and study the effect of hail on photovoltaic solar panels are described. Simulated hail stones (frozen ice spheres projected at terminal velocity) or steel balls were applied by air guns, gravity drop, or static loading. Tests with simulated hail and steel balls yielded different results. The impact strength of 10 commercially available flat-plate photovoltaic modules was tested. It was found that none of the six panel designs incorporating clear potting silicone material as the outermost layer remained undamaged by 1-in. simulated hailstones, while a photovoltaic module equipped with a 0.188-in.-thick acrylic cover sheet would be able to withstand the impact of a 2-in.-diameter hailstone.

Moore, D.↗
NASA NTRS1991

Atomic oxygen effects on SiO(x) coated Kapton for photovoltaic arrays in low earth orbit

Commercially applied SiOx was evaluated as a protective coating for the polyimide Kapton solar array blankets for Space Station Freedom. Three different rolls of coated material were tested in a plasma asher to determine their durability to attack by atomic oxygen. Mass loss data indicated that all of the coatings tested would structurally survive for 15 years in LEO (low earth orbit), except for one which had several uncoated lines across the sample which were caused by ridgelanes in the Kapton. It appears that the size rather than number of defects alone effects the mass loss the most. Careful handling of the material after coating and during processing may be critical for array survival.

Rutledge, Sharon K.↗
DOE OSTI2024

Triple Effect Economics: How Do Electric Vehicles, Solar Photovoltaics, and Work-from-Home Transform Household Electricity Cost?

Solutions for deep decarbonization need to be affordable as well as sustainable to garner widespread adoption. The past two decades have seen the introduction of new technologies and paradigms such as electric vehicles (EVs), solar photovoltaics (PVs), and increased work-from-home (WFH), which impact a household's overall energy consumption and cost in different ways. However, much attention has not been paid to explore the joint impact these technologies have on a household's electricity cost burden. Leveraging the 2020 Residential Energy Consumption Survey (RECS), this study presents an integrated model to unravel the extent to which the bundled adoption of EV-PV and stay-at-home decisions impact the total electricity cost of households. National level RECS data revealed that, compared to the baseline (i.e., households that did not own any of these technologies), households that own EVs, PVs, and engage in WFH observed a 13.5% decline in their electricity bills, despite a 25% increase in electricity consumption. The model results indicated that bundled adoption of EVs-PVs reduces electricity costs more significantly for a household, compared to the increased costs imposed by more household members staying at home. This holistic assessment presents an opportunity for decision makers to contextualize the changing energy costs and design effective strategies to foster a sustainable and cost saving mechanism. Policies such as bundled incentivization to motivate co-adoption, education about energy-management strategies, and add-on subsidies to adopt energy-efficient appliances, will not only accelerate decarbonization but increase household financial savings.

ADVANCED PROPULSION SYSTEMS,ENERGY PLANNING, POLIC↗
NASA NTRS1971

Thermally restorable optical degradation effects in heat-treated Cu2S-CdS crystal heterojunctions.

We have shown that heat treatment alone does not produce appreciable degradation of the short-circuit current in Cu2S-CdS single-crystal photovoltaic heterojunctions. The degradation, which has been commonly observed, is the result of optically induced effects in the heat-treated cell, subsequent to the heat treatment. These optically induced effects can be correlated with photochemical changes induced in single crystals of CdS:Cd:Cu in which the density of Cu acceptors exceeds the density of excess-Cd donors. Major conclusions about the mechanism of the photovoltaic effect and heat-treatment processes can be drawn.

Kanev, S. K.↗
DOE OSTI2020

Quantum Mechanical Evaluation of CZTS Properties for Photovoltaic Applications

As a quaternary semiconductor, CZTS (Cu 2 ZnSnS 4 ) shows promise as a thin-film solar cell material. The constituent elements in CZTS are abundant and non-toxic, and CZTS has an ideal band gap (~1.5 eV) for solar cell applications, which produces a large absorption coefficient. Unfortunately, the low efficiencies and difficulties in synthesizing the desired crystallographic phase (kesterite) and the associated formation of antisite defects limit its deployment. Using theoretical and computational tools, we investigated these current limitations, explored strategies to resolve these issues, and developed design guidelines to improve the efficiency of CZTS-based sunlight absorbers. We first sought to understand the challenges associated with synthesizing the kesterite phase and proposed ways to favor kesterite growth, thus adding to the understanding of CZTS photovoltaics. We also analyzed the major limitations at the atomic scale lowering the efficiency of CZTS: the low open-circuit voltage (V oc ) and the short carrier lifetime, thus addressing the technical effectiveness of CZTS photovoltaics. We believe the latter is due to Shockley-Read-Hall (SRH) recombination centers associated with point defects. We also studied the electronic structure of interfaces and defects introducing such recombination centers, and explored doping strategies to reduce SRH recombination. Ultimately, these efforts will benefit the public by contributing to the development of cheap and efficient solar energy conversion technologies made from abundant, non-toxic materials.

14 SOLAR ENERGY↗
DOE OSTI2022

Electrical edge effect induced photocurrent overestimation in low-light organic photovoltaics

In many literatures, the short-circuit current (J SC ) of indoor organic photovoltaics is overestimated, leading to severely wrong device performance evaluation and analysis. In this work, based on the equivalent circuit model, we demonstrate that electrical edge effect is sensitive to both transverse surface resistance and light intensity. At low light intensity, the electrical edge effect could lead to J SC being significantly overestimated, i.e., by 100% and even more. We show that for a PM6:Y6 device capped with a MoOX layer, when measured under 0.01 sun, the usually overlooked interface doping mechanism would lead to J SC and PCE overestimation by 51% and 15%, respectively. Besides, we show that the magnitude of J SC overestimation drastically increases with high photoactive-layer surface roughness. This work emphasized the significant electrical edge effect on J SC evaluations for low-light solar cells and is conducive to understanding the intrinsic mechanism of edge effect, promoting a healthier development of organic photovoltaics.

14 SOLAR ENERGY↗
NASA NTRS1995

Photoconductive and photovoltaic response of high-dark-resistivity 6H-SiC devices

The optoelectronic properties of high-resistivity p-type hexagonal silicon carbide (6H-SiC) have been investigated using lateral photoconductive switches. Both photovoltaic and photoconductive effects are reported, measured at 337 nm, which is above the 6H-SiC absorption edge. These photoconductive switches have been fabricated with dark resistances of up to 1 M omega; photoconductive switching efficiencies of more than 80% have been achieved. In addition, these devices displayed a high-speed photovoltaic response to nanosecond laser excitations in the ultraviolet spectral region; in particular, the observed photovoltaic response pulse width can be shorter than the exciting laser pulse width. This subnanosecond photovoltaic response has been modeled and good qualitative agreement with experiment has been obtained.

Cho, Pak S.↗
DOE OSTI2025

Defect levels and self-compensation in iodine-doped CdTe single crystals

This study systematically documents defect levels in n-type iodine-doped cadmium telluride (CdTe:I) crystals as measured by thermoelectric effect spectroscopy, Hall-effect measurements, and photoluminescence and calculated by density functional theory. The primary donor, I Te , was identified with an activation energy of ∼0.05 eV (measured)/∼0.13 eV (calculated). Deep acceptor states, V Cd and I Te –V Cd complex, exhibited activation energies of ∼0.1 eV (measured)/∼0.19 eV (calculated) and ∼0.12 eV (measured)/∼0.24 eV (calculated), respectively. Self-compensation and Fermi level pinning were observed at ∼0.7 eV (measured)/∼1.08 eV (calculated), contributing to high resistivity in as-grown samples. Post-growth Cd annealing effectively removes compensation centers, releases iodine donors, and significantly reduces resistivity, resulting in an ideal n-type solar cell material.

Cd annealing↗
DOE OSTI2021

Highly Efficient Ternary Solar Cells with Efficient Förster Resonance Energy Transfer for Simultaneously Enhanced Photovoltaic Parameters

Introducing a third component into organic bulk heterojunction solar cells has become an effective strategy to improve photovoltaic performance. Meanwhile, the rapid development of non-fullerene acceptors (NFAs) has pushed the power conversion efficiency (PCE) of organic solar cells (OSCs) to a higher standard. In this study, a series of fullerene-free ternary solar cells are fabricated based on a wide bandgap acceptor, IDTT-M, together with a wide bandgap donor polymer PM6 and a narrow bandgap NFA Y6. Insights from the morphological and electronic characterizations reveal that IDTT-M has been incorporated into Y6 domains without disrupting its molecular packing and sacrificing its electron mobility and work synergistically with Y6 to regulate the packing pattern of PM6, leading to enhanced hole mobility and suppressed recombination. IDTT-M further functions as an energy-level mediator that increases open-circuit voltage ( V OC ) in ternary devices. In addition, efficient Förster resonance energy transfer (FRET) between IDTT-M and Y6 provides a non-radiative pathway for facilitating exciton dissociation and charge collection. As a result, the optimized ternary device features a significantly improved PCE up to 16.63% with simultaneously enhanced short-circuit current ( J SC ), V OC , and fill factor (FF).

36 MATERIALS SCIENCE↗