T. A. Gessert

National Renewable Energy Laboratory

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T. J. Coutts

Centre Hospitalier de l’Université de Montréal

R. G. Dhere

National Renewable Energy Laboratory

Teresa M. Barnes

National Renewable Energy Laboratory

Helio Moutinho

National Renewable Energy Laboratory

M. W. Wanlass

National Renewable Energy Laboratory

A. Duda

Oil and Gas Institute - National Research Institute

James M. Burst

National Renewable Energy Laboratory

R. Noufi

National Renewable Energy Laboratory

Wyatt K. Metzger

National Renewable Energy Laboratory

Darius Kuciauskas

National Renewable Energy Laboratory

Cooperative Institutions

National Renewable Energy Laboratory

176

Colorado School of Mines

Office of Scientific and Technical Information

National Technical Information Service

University of Illinois Urbana-Champaign

Corning (United States)

EPIR Technologies (United States)

Oak Ridge National Laboratory

Colorado State University

Arizona State University

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High-efficiency, flexible CdTe solar cells on ultra-thin glass substrates

Applied Physics Letters (2015)

Hasitha Mahabaduge W. L. Rance James M. Burst Matthew O. Reese D. M. Meysing

Flexible, high-efficiency, low-cost solar cells can enable applications that take advantage of high specific power, flexible form factors, lower installation and transportation costs. Here, we report a certified record efficiency of 16.4% for a flexible CdTe solar cell that is a marked improvement over the previous standard (14.05%). The improvement was achieved by replacing chemical-bath-deposited CdS with sputtered CdS:O and also replacing the high-temperature sputtered ZnTe:Cu back contact layer with co-evaporated and rapidly annealed ZnTe:Cu. We use quantum efficiency and capacitance-voltage measurements combined with device simulations to identify the reasons for the increase in efficiency. Both device simulations and experimental results show that higher carrier density can quantitatively account for the increased open circuit voltage (VOC) and Fill Factor (FF), and likewise, the increase in short circuit current density (JSC) can be attributed to the more transparent CdS:O.

Cadmium telluride photovoltaics

Quantum Efficiency

Open-circuit voltage

10.1063/1.4916634

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Citations (121)

Small-scale production of 4-cm/sup 2/ ITO/InP photovoltaic solar cells

T. A. Gessert X. Li T. J. Coutts P. W. Phelps N. Tzafaras

The procedures and results of a project that produced large-area (4-cm/sup 2/) cells using the sputtering process used to form small-area indium tin oxide (ITO)/InP solar cells are described. Although only a small number of the 4-cm/sup 2/ ITO/InP cells (approximately 10 cells total) were fabricated, the efficiency of the best cell compares favorably with the best result reported from a larger production of approximately 1300 2-cm/sup 2/ cells in which the junction was fabricated through a closed-ampoule diffusion process. The average cell efficiency is determined to be 15.5%, with a standard deviation of 0.35%. The highest cell performance obtained is 16.1% AM0 (SERI measurement). Preliminary dark I-V data analysis indicates that the cells demonstrate near-ideal characteristics, with a diode-ideality factor and reverse-saturation current density of 1.02 and 1.1 *10/sup -12/ mAcm/sup -2/, respectively.< >

Indium tin oxide

Saturation current

Ampoule

Indium phosphide

Open-circuit voltage

10.1109/iciprm.1991.147287

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Citations (1)

Determination of Cu in CdTe/CdS devices before and after accelerated stress testing

S. Asher Falah S. Hasoon T. A. Gessert Matthew Young P. Sheldon

The distribution of Cu before and after accelerated stress testing of high-efficiency CdTe/CdS solar cells has been studied using high mass resolution secondary ion mass spectrometry (SIMS). Standard high-efficiency CdTe/CdS devices were used in this work. Back contacts were graphite paste with varying amounts of Cu added in the form of HgTe:Cu powder. The contacts were applied to the devices after back-surface treatment (NP etch). In one device, no intentional Cu was added to the graphite paste. The devices were stressed at open-circuit voltage in light and at 100/spl deg/C for /spl sim/1000 hours. SIMS depth profiles were performed on devices after stressing and also on companion devices that were not stressed. The stressed devices show an accumulation of Cu in the CdS layer. Copper levels in the CdS are correlated with the amount of Cu in the graphite paste contact, with higher Cu in the contact resulting in more Cu in the CdS. The Cu level in the CdTe layer is shown to be relatively constant for all devices. The Cu levels in these devices are quantified to provide absolute concentrations.

Cadmium telluride photovoltaics

Open-circuit voltage

10.1109/pvsc.2000.915876

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Citations (30)

Sulfur hexafluoride (SF<inf>6</inf>) as fluorine dopant precursor for production of fluorine doped tin oxide films by MOCVD

Carrie Wyse Robert Torres Teresa M. Barnes Marty Scott M. R. Young

SF ₆ was investigated as an alternative F source for preparing fluorine doped tin oxide films (SnO ₂ :F). SnO ₂ :F films were prepared on glass by low pressure MOCVD using tetramethyltin (Sn(CH ₃ ) ₄ ) and O ₂ with SF ₆ between 500°C and 650°C and 10-65 mol% SF ₆ . These were compared to un-doped SnO ₂ and SnO ₂ :F grown with CBrF ₃ . SF ₆ required higher thermal activation than CBrF ₃ . High electron mobility (~40 cm ² /V-s) and low resistance (6.5×10 ^-3 ¿-cm) were achieved with SF ₆ at ¿600°C. at 550°C and below, mobility was on the order of 4 cm ² /V-s. Carrier concentrations were on the order of 10 ¹⁹ cm ^-3 , compared to 10 ²⁰ cm ^-3 for CBrF ₃ doped films. Optical transmission, reflectance and absorption spectra demonstrated transmittance of 80% in the visible spectrum. XRD showed SF ₆ generated films of different crystal structure than CBrF ₃ . SIMS Showed a uniform F concentration of 1.5×10 ¹⁹ atom/cm ³ from SF ₆ , but SF ₆ did not incorporate as much F into the films as CBrF ₃ (7.5×10 ²⁰ atoms/cm ³ ). Sulfur contamination was not found.

10.1109/pvsc.2009.5411291

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Citations (1)

A comparative study of metal-semiconductor-metal photodetectors on GaAs with indium-tin-oxide and Ti/Au electrodes

IEEE Photonics Technology Letters (1992)

Jai Woong Seo A. Ketterson D. G. Ballegeer K. Y. Cheng I. Adesida

Metal-semiconductor-metal (MSM) photodiodes with interdigitated indium-tin-oxide (ITO) electrodes have been fabricated on undoped GaAs using reactive-ion-etching in a methane plasma. The responsivity of ITO MSMs is measured to be approximately 0.8 A/W, which is twice that of conventional Ti/Au MSMs under normal operational bias conditions at lambda =850 nm. This higher responsivity is attributed to the transparency of the ITO electrodes. ITO MSMs exhibited a linear optical response over a wider bias range than Ti/Au MSMs. Also, a higher breakdown voltage was measured for ITO MSMs. The bandwidths of ITO and Ti/Au MSMs fabricated on the same semiconductor layer with 1- mu m fingers and spaces were measured to be 6 and 9 GHz, respectively. The slower response of the ITO MSMs is due to the longer transit time of the carriers generated beneath the ITO electrodes.< >

Indium tin oxide

Photodiode

10.1109/68.149898

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Citations (38)

Performance of transparent conductors on flexible glass and plastic substrates for thin film photovoltaics

2017 IEEE 44th Photovoltaic Specialist Conference (PVSC) (2014)

James M. Burst W. L. Rance D. M. Meysing Colin A. Wolden Wyatt K. Metzger

High-performance transparent conductive indium-tin-oxide (ITO) films on flexible glass have been flextested to 25–50k bend cycles without breakage, and with ∼0.1% change in sheet resistance. In contrast, commercial ITO/PET samples undergo ∼50–100% increase in sheet resistance in the same test, indicating that such coatings/substrates may not be acceptable for use in some products or fabrication procedures. The flexible glass substrate enables high-temperature processing, which facilitates the high performance of the coatings. Measurements of the volume resistivity and water vapor transmission rate (WVTR) indicate that Corning ^® Willow ^® Glass is suitable as a PV substrate material without need for barrier coatings or glass lamination.

Indium tin oxide

Lamination

10.1109/pvsc.2014.6925223

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Citations (13)

Analysis of the Junction Properties of CdS/CdTe Devices in Substrate and Superstrate Configurations

World Conference on Photovoltaic Energy Conversion (2011)

R. G. Dhere Joel N. Duenow Clay DeHart J. V. Li Darius Kuciauskas

The best efficiency of CdS/CdTe devices fabricated in the substrate configuration reported to date is about 8%, which is about half the 17.3% reported for the conventional superstrate configuration. The performance of substrate devices is affected by lower open-circuit voltage (Voc), about 700 mV, and low fill factor (FF), which indicates that these devices are primarily limited by non-ideal junction properties and possibly by the ohmic contact to CdTe. In our study of the junction properties of superstrate devices, we show that lower-Voc devices ( 800 mV, the junction is between an n-type, Te-rich CdSTe alloy with a bandgap of 1.45 eV and p-type CdTe with a bandgap of 1.5 eV. Because the crystal structure of both the Te-rich alloy and the CdTe is cubic zinc blende, and the lattice mismatch between the two is minimal, the device in this case can be considered a quasi-homojunction. These higher-Voc devices are therefore affected less by the highmore » charged defect density at the hetero-interface, which lies outside of the depletion region. We present analysis of the junction properties of our recent and improved substrate-configuration devices with Voc well in excess of 800 mV, FF approaching 60%, and efficiencies around 10%. We also compare devices fabricated in both the substrate and superstrate configurations and with comparable Voc in the range of 700 to more than 800 mV. Photoluminescence (PL) and temperature-dependent PL, current density-voltage and quantum efficiency analysis, and modulated reflectance measurements are used to study device properties.« less

Homojunction

Cadmium telluride photovoltaics

Ohmic contact

Wide-bandgap semiconductor

Quantum Efficiency

10.4229/26theupvsec2011-3do.9.2

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Citations (3)

Development of CdS/CdTe Thin Film Devices for St. Gobain Coated Glass: Cooperative Research and Development Final Report, CRADA Number CRD-08-317

T. A. Gessert

Research performed at NREL to produce CdS/CdTe devices on St. Gobain coated-glass material to establish a baseline CdS/CdTe device process and determine baseline device performance parameters on St. Gobain material. Performance of these baseline devices compared to similar devices produced by applying the established baseline CdS/CdTe process on alternative St. Gobain coated-glass materials.

Cadmium telluride photovoltaics

Baseline (sea)

10.2172/1039787

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Citations (0)

High-Efficiency CdTe Polycrystalline Thin-Film Solar Cells with an Ultra-Thin Cu_xTe Transparent Back-Contact

MRS Proceedings (2005)

Xin Wu Jie Zhou A. Duda J. Keane T. A. Gessert

Cadmium telluride photovoltaics

Tandem

10.1557/proc-865-f114

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Citations (5)

Grid metallization and antireflection coating optimization for concentrator and one-sun photovoltaic solar cells

Journal of Vacuum Science & Technology A Vacuum Surfaces and Films (1992)

T. A. Gessert T. J. Coutts

In photovoltaic (PV) solar cell research, often the mechanisms of junction formation are studied intensively, while the design of the grid and the antireflection coating (ARC) are somewhat neglected. This is usually because, at the research stage, fundamental information about the junction parameters of novel device materials is more essential than the need to produce high-efficiency devices. Additionally, the equipment and expertise necessary to enable state-of-the-art processing is relatively specialized and often not available to the PV researcher. Nevertheless, during the past few years, many PV research technologies have begun to incorporate optimally designed ARCs and very high-quality metallization, involving processes more typically associated with the micoelectronics industry. Partly because of this, significant improvements in conversion efficiencies have been reported in several key solar cell material systems. In this paper, the models and techniques necessary to design and optimize metal contacts and ARCs for PV solar cells are reviewed and discussed. Additionally, similarities and differences between grid metallizations of cells used under optical concentration and one sun are identified. Through these discussions, the advantages of several recently developed metallization and ARC techniques are reviewed, including very-fine linewidth, buried-contact metallizations, metallizations typically used in the thin-film solar cell industry, and short-circuit current contour modeling for ARC optimization.

Concentrator

10.1116/1.578018

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Citations (21)