A5000834901- Chalcogenide Semiconductor Thin Films
- Quantum Dots Synthesis And Properties
- Copper-based nanomaterials and applications
- ZnO doping and properties
- Perovskite Materials and Applications
- Advanced Semiconductor Detectors and Materials
- Semiconductor materials and devices
- Semiconductor materials and interfaces
- Silicon and Solar Cell Technologies
- Gas Sensing Nanomaterials and Sensors
- solar cell performance optimization
- Inorganic Chemistry and Materials
- Catalytic Processes in Materials Science
- Electronic and Structural Properties of Oxides
- Ga2O3 and related materials
- Advanced Photocatalysis Techniques
- Conducting polymers and applications
- Thin-Film Transistor Technologies
- Advanced Materials Characterization Techniques
- Organic Electronics and Photovoltaics
- Machine Learning in Materials Science
- Electron and X-Ray Spectroscopy Techniques
- Diamond and Carbon-based Materials Research
- Boron and Carbon Nanomaterials Research
- Metal Extraction and Bioleaching
National Renewable Energy Laboratory
2016-2025
University of Maryland, College Park
2011
Office of Scientific and Technical Information
2005
Pacific Northwest National Laboratory
1999-2005
Environmental Molecular Sciences Laboratory
1999-2003
University of Illinois Chicago
1996-2001
University of Central Florida
1992
Abstract We report a new record total‐area efficiency of 19·9% for CuInGaSe 2 ‐based thin‐film solar cells. Improved performance is due to higher fill factor. The device was made by three‐stage co‐evaporation with modified surface termination. Growth conditions, analysis, and basic film characterization are presented. Published in 2008 John Wiley & Sons, Ltd.
Abstract We report the growth and characterization of record‐efficiency ZnO/CdS/CuInGaSe 2 thin‐film solar cells. Conversion efficiencies exceeding 19% have been achieved for first time, this result indicates that 20% goal is within reach. Details experimental procedures are provided, material device data presented. Published in 2003 by John Wiley & Sons, Ltd.
We describe the structural, optical, and electrical properties of high-quality films PbSe nanocrystals fabricated by a layer-by-layer (LbL) dip-coating method that utilizes 1,2-ethanedithiol (EDT) as an insolubilizing agent. Comparative characterization nanocrystal made spin-coating LbL process shows EDT quantitatively displaces oleic acid on surface, causing large volume loss electronically couples while severely degrading their positional crystallographic order films. Field-effect...
We have examined the interaction of molecular oxygen with TiO2(110) surface using temperature-programmed desorption (TPD), isotopic labeling studies, sticking probability measurements, and electron energy loss spectroscopy (ELS). Molecular does not adsorb on in temperature range between 100 300 K unless vacancy sites are present. These defects generated by annealing crystal at 850 K, can be quantified reliably water TPD. Adsorption O2 120 a 8% vacancies (about 4 × 1013 sites/cm2) occurs an...
We report on the synthesis and electrochemical properties of oriented NiO-TiO(2) nanotube (NT) arrays as electrodes for supercapacitors. The morphology films prepared by electrochemically anodizing Ni-Ti alloy foils was characterized scanning transmission electron microscopies, X-ray diffraction, photoelectron spectroscopies. morphology, crystal structure, composition NT were found to depend preparation conditions (anodization voltage postgrowth annealing temperature). Annealing as-grown a...
In this study we show that molecular oxygen reacts with bridging OH (OHbr) groups formed as a result of water dissociation at vacancy defects on the surface rutile TiO2(110). The electronic structure an defect TiO2(110) is essentially same electron trap states detected photoexcited or sensitized TiO2 photocatalysts, being Ti3+ in nature. Electron energy loss spectroscopy (EELS) measurements, agreement valence band photoemission results literature, indicate sites has little no impact these...
We describe the structural, optical, and electrical properties of films spin-cast, oleate-capped PbSe nanocrystals that are treated thermally or chemically in solutions hydrazine, methylamine, pyridine to produce electronically coupled nanocrystal solids. Postdeposition heat treatments trigger sintering at approximately 200 degrees C, before a substantial fraction oleate capping group evaporates pyrolyzes. The sintered have large hole density highly conductive. Most amine preserve size...
The n-type transition metal oxides (TMO) consisting of molybdenum oxide (MoO(x)) and vanadium (V(2)O(x)) are used as an efficient hole extraction layer (HEL) in heterojunction ZnO/PbS quantum dot solar cells (QDSC). A 4.4% NREL-certified device based on the MoO(x) HEL is reported with Al back contact material, representing a more than 65% efficiency improvement compared case Au contacting PbS (QD) directly. We find acting mechanism to be dipole formed at interface enhancing band bending...
PbSe quantum dot (QD) field effect transistors (FETs) with air-stable electron mobilities above 7 cm(2) V(-1) s(-1) are made by infilling sulfide-capped QD films amorphous alumina using low-temperature atomic layer deposition (ALD). This high mobility is achieved combining strong electronic coupling (from the ultrasmall sulfide ligands) passivation of surface states ALD coating. A series control experiments rule out alternative explanations. Partial tunes electrical characteristics FETs.
CdTe-based solar cells exhibiting 19% power conversion efficiency were produced using widely available thermal evaporation deposition of the absorber layers on SnO2-coated glass with or without a transparent MgZnO buffer layer. Evaporating CdSe and CdTe sequentially by subsequent CdCl2 annealing establishes efffective CdSeTe band grading as well dense, large-grain films. These results show that high-performance II–VI photovoltaics can be made inexpensive, commercially systems need to build...
Nitrogen-doped films of ZnO grown by two methods, metalorganic chemical vapor deposition (MOCVD) and reactive sputtering, were studied with x-ray ultraviolet photoelectron spectroscopy (XPS UPS). Systematic differences in the N states observed between sputtering MOCVD: only whereas four MOCVD films. To aid assignment states, photoemission data from polycrystalline compared taken on N2+-implanted Zn metal ZnO. High-resolution core level spectra N1s region indicated that nitrogen can occupy at...
Using X-ray and ultraviolet photoelectron spectroscopy, the surface band positions of solution-processed CH3NH3PbI3 perovskite thin films deposited on an insulating substrate (Al2O3), various n-type (TiO2, ZrO2, ZnO, F:SnO2 (FTO)) substrates, p-type (PEDOT:PSS, NiO, Cu2O) substrates are studied. Many-body GW calculations valence density states, with spin–orbit interactions included, show a clear correspondence our experimental spectra used to confirm assignment maximum. These...
Abstract Iron pyrite (cubic FeS 2 ) is a promising candidate absorber material for earth‐abundant thin‐film solar cells. In this report, single‐phase, large‐grain, and uniform polycrystalline thin films are fabricated on glass molybdenum‐coated substrates by atmospheric‐pressure chemical vapor deposition (AP‐CVD) using the reaction of iron(III) acetylacetonate tert ‐butyl disulfide in argon at 300 °C, followed sulfur annealing 500–550 °C to convert marcasite impurities pyrite. The...
Thin films of colloidal semiconductor nanocrystals (NCs) are inherently metatstable materials prone to oxidative and photothermal degradation driven by their large surface-to-volume ratios high surface energies. (1) The fabrication practical electronic devices based on NC solids hinges preventing oxidation, diffusion, ripening, sintering, other unwanted physicochemical changes that can plague these materials. Here we use low-temperature atomic layer deposition (ALD) infill conductive PbSe...
Nanoporous, catalyst-free BiVO<sub>4</sub> films made by a simple spin coating process show hole-limited charge transport quantum efficiency of ∼70% and >60% transfer for oxidizing water.
Iron pyrite (cubic FeS2) is a promising candidate absorber material for earth-abundant thin-film solar cells. Here, we report on phase-pure, large-grain, and uniform polycrystalline films that are fabricated by solution-phase deposition of an iron(III) acetylacetonate molecular ink followed sequential annealing in air, H2S, sulfur gas at temperatures up to 550 °C. Phase elemental compositions the characterized conventional synchrotron X-ray diffraction, Raman spectroscopy, Auger electron...
We use a high signal-to-noise X-ray photoelectron spectrum of bulk PbS, GW calculations, and model assuming parabolic bands to unravel the various ultraviolet spectral features PbS as well determine how best analyze valence band region quantum dot (QD) films. spectroscopy (XPS UPS) are commonly used probe difference between Fermi level maximum (VBM) for crystalline thin-film semiconductors. However, we find that when standard XPS/UPS analysis is results often unrealistic due low density...
Recombination is critically limiting in CdTe devices such as solar cells and detectors, with much of it occurring at or near the surface. In this work, we explore different routes to passivate p-type surfaces without any intentional extrinsic passivation layers. To provide deeper insight into routes, uniquely correlate a set characterization methods: surface analysis time-resolved spectroscopy. We study two model systems: nominally undoped single crystals large-grain polycrystalline films....
Mg <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Zn xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> O (MZO) shows great promise to replace CdS as a buffer layer in CdTe-based solar cells. It is more transparent, and the MZO bandgap electron density can be tuned, thus providing flexibility controlling conduction band offsets recombination rates between transparent conductive oxide/MZO MZO/CdSeTe interfaces. Integrating this...
Oxide materials with the perovskite structure have been used in sensors and actuators for half a century, halide perovskites transformed photovoltaics research past decade. Nitride computationally predicted to be stable, but few synthesized, their properties remain largely unknown. We synthesized characterized nitride lanthanum tungsten (LaWN3) form of oxygen-free sputtered thin films, according spectroscopy, scattering, microscopy techniques. report large piezoelectric response measured...
We have fabricated nitrogen-doped zinc oxide (ZnO) films that demonstrate p-type behavior by using metalorganic chemical vapor deposition. In our experiment, diethylzinc is used as a Zn precursor, and NO gas to supply both O N form N-doped ZnO (ZnO:N) film. With these precursors, we routinely reached an concentration in the of about 1–3 at. %. When level higher than 2 %, characteristics. The carrier varies from 1.0×1015 1.0×1018 cm−3, mobilities are mainly 10−1 cm2 V−1 s−1 range. lowest film...