P.J. Resnick

Sandia National Laboratories, Albuquerque, New Mexico, United States

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Publications (37)22.86 Total impact

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    ABSTRACT: Microsystems-enabled photovoltaics (MEPV) has great potential to meet the increasing demands for light-weight, photovoltaic solutions with high power density and efficiency. This paper describes effective failure analysis techniques to localize and characterize nonfunctional or underperforming MEPV cells. The defect localization methods such as electroluminescence under forward and reverse bias, as well as optical beam induced current using wavelengths above and below the device band gap, are presented. The current results also show that the MEPV has good resilience against degradation caused by reverse bias stresses.
    IEEE Journal of Photovoltaics 01/2014; 4(1):470-476. DOI:10.1109/JPHOTOV.2013.2284864 · 3.00 Impact Factor
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    ABSTRACT: We present ultra-thin single crystal mini-modules built with specific power of 450 W/kg capable of voltages of >1000 V/cm2. These modules are also ultra-flexible with tight bending radii down to 1 mm. The module is composed of hundreds of back contact microcells with thicknesses of approximately 20 μm and diameters between 500-720 μm. The cells are interconnected to a flexible circuit through solder contacts. We studied the characteristics of several mini-modules through optical inspection, evaluation of quantum efficiency, measurement of current-voltage curves, and temperature dependence. Major efficiency losses are caused by missing cells or non-interconnected cells. Secondarily, damage incurred during separation of 500 μm cells from the substrate caused material detachment. The detachment induced higher recombination and low performance. Modules made with the larger cells (720 μm) performed better due to having no missing cells, no material detachment and optimized AR coatings. The conversion efficiency of the best mini module was 13.75% with a total Voc = 7.9 V.
    2013 IEEE 39th Photovoltaic Specialists Conference (PVSC); 06/2013
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    ABSTRACT: We report on a demonstration prototype module created to explore the viability of using microscale solar cells combined with microlens array concentrators to create a thin, flat-plate concentrator module with a relatively large acceptance angle for use with coarse two-axis tracking systems designed for flat-plate, one-sun modules. The demonstration module was comprised of an array of 216 cell/microlens units and was manufactured using standard tools common to the integrated circuit, microelectromechanical system (MEMS), and electronics assembly industries. The module demonstrated an acceptance angle of ±4°, an optical concentration level of 36X, and a focal depth of 13.3 mm. The acceptance angle and focal depth of the system successfully demonstrated adequate performance for integration into a system using a coarse two-axis tracker for flat-plate modules. To fully take advantage of this system approach, significant future work is required to reduce optical losses, increase cell and module efficiency, reduce the focal length to approximately 5 mm, and increase the concentration level to greater than 100X while maintaining an acceptance angle of at least ±2°.
    2013 IEEE 39th Photovoltaic Specialists Conference (PVSC); 06/2013
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    ABSTRACT: Microsystems-enabled photovoltaic (MEPV) technology is a promising approach to lower the cost of solar energy to competitive levels. This paper describes current development efforts to leverage existing silicon integrated circuit (IC) failure analysis (FA) techniques to study MEPV devices. Various FA techniques such as light emission microscopy and laser-based fault localization were used to identify and characterize primary failure modes after fabrication and packaging. The FA results provide crucial information used in provide corrective actions and improve existing MEPV fabrication techniques.
    Reliability Physics Symposium (IRPS), 2013 IEEE International; 01/2013
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    ABSTRACT: Back-contacted, ultrathin (<10 mu m), and submillimeter-sized solar cells made with microsystem tools are a new type of cell that has not been optimized for performance. The literature reports efficiencies up to 15% using thicknesses of 14 mu m and cell sizes of 250 mu m. In this paper, we present the design, conditions, and fabrication parameters necessary to optimize these devices. The optimization was performed using commercial simulation tools from the microsystems arena. A systematic variation of the different parameters that influence the performance of the cell was accomplished. The researched parameters were resistance, Shockley-Read-Hall (SRH) lifetime, contact separation, implant characteristics (size, dosage, energy, and ratio between the species), contact size, substrate thickness, surface recombination, and light concentration. The performance of the cell was measured with efficiency, open-circuit voltage, and short-circuit current. Among all the parameters investigated, surface recombination and SRH lifetime proved to be the most important. Through completing the simulations, an optimized concept solar cell design was introduced for two scenarios: high and low quality materials/passivation. Simulated efficiencies up to 23.4% (1sun) and 26.7% (100suns) were attained for 20-mu m-thick devices. Copyright (c) 2012 John Wiley & Sons, Ltd.
    Progress in Photovoltaics Research and Applications 05/2012; 21(5). DOI:10.1002/pip.2214 · 7.71 Impact Factor
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    ABSTRACT: We present the experimental procedure to create lattice mismatched multijunction photovoltaic (PV) cells using 3D integration concepts. Lattice mismatched multijunction photovoltaic (PV) cells with decoupled electrical outputs could achieve higher efficiencies than current-matched monolithic devices. Growing lattice mismatched materials as a monolithic structure generates defects and decreases performance. We propose using methods from the integrated circuits and microsystems arena to produce the PV cell. The fabricated device consists of an ultrathin (6 μm) series connected InGaP/GaAs PV cell mechanically stacked on top of an electrically independent silicon cell. The InGaP/GaAs PV cell was processed to produce a small cell (750 μm) with back-contacts where all of the contacts sit at the same level. The dual junction and the silicon (c-Si) cell are electrically decoupled and the power from both cells is accessible through pads on the c-Si PV cell. Through this approach, we were able to fabricate a functional double junction PV cell mechanically attached to a c-Si PV cell with independent connections.
    Photovoltaic Specialists Conference (PVSC), 2012 38th IEEE; 01/2012
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    ABSTRACT: This paper reports the radial bulk-mode vibrations in a gate-all-around (GAA) silicon nanowire (SiNW) transistor at 25.3GHz, with a quality factor of ∼850 measured in air. The radial bulk-mode resonance is excited capacitively in the SiNW using the surrounding gate and gate dielectric as the transducer; the output is sensed piezoresistively by modulating the drain current in SiNW. The SiNWs are defined using standard lithography in a top-down front-end CMOS process, which allows for resonators with different frequencies to be fabricated on the same chip.
    Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS) 01/2012; DOI:10.1109/MEMSYS.2012.6170423
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    ABSTRACT: We present an approach to create ultrathin (<;20 μm) and highly flexible crystalline silicon sheets on inexpensive substrates. We have demonstrated silicon sheets capable of bending at a radius of curvature as small as 2 mm without damaging the silicon structure. Using microsystem tools, we created a suspended submillimeter honeycomb-segmented silicon structure anchored to the wafer only by small tethers. This structure is created in a standard thickness wafer enabling compatibility with common processing tools. The procedure enables all the high-temperature steps necessary to create a solar cell to be completed while the cells are on the wafer. In the transfer process, the cells attach to an adhesive flexible substrate which, when pulled away from the wafer, breaks the tethers and releases the honeycomb structure. We have previously demonstrated that submillimeter and ultrathin silicon segments can be converted into highly efficient solar cells, achieving efficiencies up to 14.9% at a thickness of 14 μm. With this technology, achieving high efficiency (>;15%) and highly flexible photovoltaic (PV) modules should be possible.
    IEEE Journal of Photovoltaics 07/2011; 1(1):3-8. DOI:10.1109/JPHOTOV.2011.2162973 · 3.00 Impact Factor
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    ABSTRACT: We report up to 75 times enhancement in emission from lithographically produced photonic crystals with postprocessing close-packed colloidal quantum-dot incorporation. In our analysis, we use the emission from a close-packed free-standing film as a reference. After discounting the angular redistribution effect, our analysis shows that the observed enhancement is larger than the combined effects of Purcell enhancement and dielectric enhancement with the microscopic local field. The additional enhancement mechanisms, which are consistent with all our observations, are thought to be spectral diffusion mediated by phonons and local polarization fluctuations that allow off-resonant excitons to emit at the cavity wavelengths.
    Journal of the Optical Society of America B 05/2011; 28(6):1365-1373. DOI:10.1364/JOSAB.28.001365 · 1.81 Impact Factor
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    ABSTRACT: Crystalline silicon solar cells 10–15 times thinner than traditional commercial c-Si cells with 14.9% efficiency are presented with modeling, fabrication, and testing details. These cells are 14 μm thick, 250 μm wide, and have achieved 14.9% solar conversion efficiency under AM 1.5 spectrum. First, modeling results illustrate the importance of high-quality passivation to achieve high efficiency in thin silicon, back contacted solar cells. Then, the methodology used to fabricate these ultra thin devices by means of established microsystems processing technologies is presented. Finally, the optimization procedure to achieve high efficiency as well as the results of the experiments carried out with alumina and nitride layers as passivation coatings are discussed.Graphical Abstract
    Solar Energy Materials and Solar Cells 02/2011; 95(2):551-558. DOI:10.1016/j.solmat.2010.09.015 · 5.03 Impact Factor
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    ABSTRACT: Microsystem-Enabled Photovoltaic (MEPV) cells allow solar PV systems to take advantage of scaling benefits that occur as solar cells are reduced in size. We have developed MEPV cells that are 5 to 20 microns thick and down to 250 microns across. We have developed and demonstrated crystalline silicon (c-Si) cells with solar conversion efficiencies of 14.9%, and gallium arsenide (GaAs) cells with a conversion efficiency of 11.36%. In pursuing this work, we have identified over twenty scaling benefits that reduce PV system cost, improve performance, or allow new functionality. To create these cells, we have combined microfabrication techniques from various microsystem technologies. We have focused our development efforts on creating a process flow that uses standard equipment and standard wafer thicknesses, allows all high-temperature processing to be performed prior to release, and allows the remaining post-release wafer to be reprocessed and reused. The c-Si cell junctions are created using a backside point-contact PV cell process. The GaAs cells have an epitaxially grown junction. Despite the horizontal junction, these cells also are backside contacted. We provide recent developments and details for all steps of the process including junction creation, surface passivation, metallization, and release.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2011; DOI:10.1117/12.876422 · 0.20 Impact Factor
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    ABSTRACT: Reducing the thickness of crystalline silicon wafers has evolved in the solar industry. As of 2010, most of the silicon solar cell companies were working with 6 inch wafers with thicknesses between 180 and 200 µm. In addition, a significant portion of the crystalline silicon material is lost during sawing. The effective material usage is equivalent to a wafer with a thickness of 310–475 µm depending on the thickness of the cut wire. Although there is a strong cost driver to use thinner wafers, handling wafers thinner than 180 µm is challenging while maintaining adequate yield. We present an approach to create ultrathin (15%), highly-flexible PV modules should be possible with this approach.
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    ABSTRACT: We present a newly developed microsystem enabled, back-contacted, shade-free GaAs solar cell. Using microsystem tools, we created sturdy 3 μm thick devices with lateral dimensions of 250 μm, 500 μm, 1 mm, and 2 mm. The fabrication procedure and the results of characterization tests are discussed below. The highest efficiency cell had a lateral size of 500 μm and a conversion efficiency of 10%, open circuit voltage of 0.9 V and a current density of 14.9 mA/cm<sup>2</sup> under one-sun illumination.
    Photovoltaic Specialists Conference (PVSC), 2010 35th IEEE; 07/2010
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    ABSTRACT: Thin and small form factor cells have been researched lately by several research groups around the world due to possible lower assembly costs and reduced material consumption with higher efficiencies. Given the popularity of these devices, it is important to have detailed information about the behavior of these devices. Simulation of fabrication processes and device performance reveals some of the advantages and behavior of solar cells that are thin and small. Three main effects were studied: the effect of surface recombination on the optimum thickness, efficiency, and current density, the effect of contact distance on the efficiency for thin cells, and lastly the effect of surface recombination on the grams per Watt-peak. Results show that high efficiency can be obtained in thin devices if they are well-passivated and the distance between contacts is short. Furthermore, the ratio of grams per Watt-peak is greatly reduced as the device is thinned.
    Photovoltaic Specialists Conference (PVSC), 2010 35th IEEE; 07/2010
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    ABSTRACT: High Purcell spontaneous emission enhancement factor of 116 is achieved by integrating a self-assembled, close packed monolayer of colloidal PbS quantum dots with a L3-type silicon photonic crystal cavity.
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    ABSTRACT: Photovoltaic (PV) power is currently two to four times the retail cost of grid power. To achieve grid cost parity requires significant PV system cost reductions. Furthermore, if solar power is to provide a significant amount of society’s power, manufacturing will need to scale up dramatically. What is needed is a low-cost, high-speed technique to create large numbers of PV panels. One current manufacturing technique that provides high-speed production of large amounts of area is roll-to-roll printing (e.g., newspaper printing). If this manufacturing concept can be applied to PV, large cost reductions are possible. There are several PV materials under development that lend themselves to “roll-to-roll” printing of PV panels. These materials include amorphous silicon, CdTe, CIGS, organic PV, and dye-sensitized PV. These materials have significant promise but also have challenges, including low efficiencies, poor reliability, and rapid degradation. We are pursuing new PV manufacturing techniques that utilize materials known to provide high efficiencies and high reliability, such as crystalline silicon and GaAs. These new techniques provide the possibility of “roll-to-roll” printing of PV modules with high-efficiency, high-reliability materials. Of the PV technologies that lend themselves to roll-to-roll printing, our technique allows the lowest balance of system cost for PV systems along with competitive $/Wpeak manufacturing costs of modules.
    64th American Chemical Society Southwest Regional Meeting; 11/2009
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    ABSTRACT: Over the last decade, thin (< 50 mm) crystalline silicon photovoltaics have been of significant interest to the research community. Crystalline silicon is able to absorb most of the solar spectrum within a few tens of microns of optical path length. Thin silicon solar cells provide reduced cost (through materials savings), lighter weight, and higher open circuit voltages. Sandia National Laboratories has introduced an innovative way to create ultra-thin, small form factor (sub-millimeter), crystalline silicon solar cells, using concepts from microsystems and MEMS. In this talk, key results from simulations of these devices will be presented and discussed. Tsuprem4 and Medici (both software by Synopsis) were used for these simulations. A variety of different designs was explored under one-sun and concentrated light scenarios to understand the design space for these ultra-thin c-Si PV cells. Several variables (e.g., surface recombination, bulk recombination, doping concentration, and thickness of the solar cell) were tested, with direct effects on performance. Due to the high surface area to volume ratio of these ultra-thin cells, surface parameters dominated the behavior of the solar cell. Varying these parameters raised conversion efficiency from < 1% to 18%. Finally, the simulations with varied surface recombination values were compared to experimental results of actual cells, where a variety of surface passivating films were explored. Simulated results were consistent with experimentally measured values.
    64th American Chemical Society Southwest Regional Meeting; 11/2009
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    ABSTRACT: We are exploring fabrication and assembly concepts developed for microsystems/MEMS technology to reduce the cost of solar PV power. These methods have the potential to reduce many system level costs of current PV systems including, among others, silicon material costs, module assembly costs, and installation costs. We have demonstrated a direct c-Si material reduction of approximately 20X (including wire-saw kerf loss and polishing loss). The cells have achieved efficiencies of almost 9% and J<sub>sc</sub> of 30 mA/cm<sup>2</sup>. We are currently using integrated-circuit (IC) fabrication tools that will lead to higher efficiencies and improved yield. These advantages and the material reduction are expected to reduce the current module manufacturing costs.
    Photovoltaic Specialists Conference (PVSC), 2009 34th IEEE; 07/2009
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    ABSTRACT: In order to observe and quantify pressure levels generated during testing of energetic materials, a sensor array with high temporal resolution (~1 ns) and extremely high pressure range (> 1 GPa) is needed. We have developed such a sensor array which utilizes a novel integrated high performance CMOS+MEMS process.
    Micro Electro Mechanical Systems, 2009. MEMS 2009. IEEE 22nd International Conference on; 03/2009
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    ABSTRACT: We have developed and demonstrated a technique for optical excitation of mechanical resonance that does not require coherent, monochromatic, or time-varying light. Previous methods for optically exciting mechanical motion in microscale devices required monochromatic, coherent light or time varying light. This technology could allow sunlight (or other ambient light source) to drive a MEMS device. It could also be used to convert sunlight to mechanical energy and subsequently to electrical energy through piezoelectric or capacitive techniques, essentially a micromechanical analog to the photovoltaic cell. We have demonstrated this method of optical excitation of a MEMS cantilever using simple cantilever beam structures fabricated using Sandia National Laboratories’ SUMMiT V™ process. The bimorph structure was created with polysilicon and aluminum. The minimum power to induce resonance was 3.5–4 mW of optical power incident on the cantilever under a vacuum of less than 1 mTorr. Resonance was observed at 45.6 kHz (slightly less than the 48.5 kHz predicted by FEA).
    ASME 2009 International Mechanical Engineering Congress and Exposition; 01/2009