|Michigan Tech's Open Sustainability Technology Lab.
Wanted: Students to make a distributed future with solar-powered open-source 3-D printing and recycling.
|This is in a series of literature reviews on InGaN solar cells, which supported the comprehensive review by D.V.P. McLaughlin & J.M. Pearce, "Progress in Indium Gallium Nitride Materials for Solar Photovoltaic Energy Conversion"Metallurgical and Materials Transactions A 44(4) pp. 1947-1954 (2013). open access |
Others: InGaN solar cells| InGaN PV| InGaN materials| InGan LEDs| Nanocolumns and nanowires| Optical modeling of thin film microstructure| Misc.
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Abstract: The thermoelectric properties of AlGaN and InGaN semiconductors are analyzed. In Author(s) analysis, the thermal conductivities, electrical conductivities, Seebeck coefficients, and figure of merits (Z*T) of AlGaN and InGaN semiconductors are computed. The electron transports in AlGaN and InGaN alloys are analyzed by solving Boltzmann transport equation, taking into account the dominant mechanisms of energy-dependent electron scatterings. Virtual crystal model is implemented to simulate the lattice thermal conductivity from phonon scattering for both AlGaN and InGaN alloys. The calculated Z*T is as high as 0.15 for optimized InGaN alloy at temperature around 1000 K. For optimized AlGaN composition, the Z*T of 0.06-0.07 can be achieved. The improved thermoelectric performance of ternary alloys over binary alloys can be attributed to the reduced lattice thermal conductivity.
Abstract: Thermoelectric (TE) properties of InxGa1−xN alloys grown by metal organic chemical vapor deposition have been investigated. It was found that as indium concentration increases, the thermal conductivity decreases and power factor increases, which leads to an increase in the TE figure of merit (ZT). The value of ZT was found to be 0.08 at 300 K and reached 0.23 at 450 K for In0.36Ga0.64N alloy, which is comparable to those of SiGe based alloys. The results indicate that InGaN alloys could be potentially important TE materials for many applications, especially for prolonged TE device operation at high temperatures, such as for recovery of waste heat from automobile, aircrafts, and power plants due to their superior physical properties, including the ability of operating at high temperature/high power conditions, high mechanical strength and stability, and radiation hardness.
Contact effects of solution-processed polymer electrodes: Limited conductivity and interfacial doping[edit | edit source]
Abstract: Contact effects between solution processed conducting polymer electrodes with semiconducting polymers in field effect transistors are investigated. Limited conductivity of polymer electrodes and interfacial doping of the active semiconducting polymer by the conducting polymer electrode are found to be two important factors in determining the performance of polymer field effect transistors with printed conducting polymer electrodes.
Abstract: The use of quantum and photon confinement has enabled a true revolution in the development of high-performance semiconductor materials and devices. Harnessing these powerful physical effects relies on an ability to design and fashion structures at length scales comparable to the wavelength of electrons (1 nm) or photons (1 m). Unfortunately, many practical optoelectronic devices exhibit intermediate sizes where resonant enhancement effects seem to be insignificant. Here, Author(s) show that leaky-mode resonances, which can gently confine light within subwavelength, high-refractive-index semiconductor nanostructures, are ideally suited to enhance and spectrally engineer light absorption in this important size regime. This is illustrated with a series of individual germanium nanowire photodetectors. This notion, together with the ever-increasing control over nanostructure synthesis opens up tremendous opportunities for the realization of a wide range of high-performance, nanowire-based optoelectronic devices, including solar cells, photodetectors, optical modulators14 and light sources.
Low-resistance ohmic contacts to p-type GaN achieved by the oxidation of Ni/Au films[edit | edit source]
Abstract: A contact has been developed to achieve a low specific contact resistance to p-type GaN. The contact consisted of a bi-layer Ni/Au film deposited on p-type GaN followed by heat treatment in air to transform the metallic Ni into NiO along with an amorphous Ni–Ga–O phase and large Au grains. A specific contact resistance as low as 4.0×10−6 Ω cm2 was obtained at 500 °C. This low value was obtained by the optimization of Ni/Au film thickness and heat treatment temperatures. Below about 400 °C, Ni was not completely oxidized. On the other hand, at temperatures higher than about 600 °C, the specific contact resistance increased because the NiO detached from p-GaN and the amount of amorphous Ni–Ga–O phase formed was more than that of the sample annealed at 500 °C. The mechanism of obtaining low-resistance ohmic contacts for the oxidized Ni/Au films was explained with a model using energy band diagrams of the Au/p-NiO/p-GaN structure.
The interdigitated back contact solar cell: A silicon solar cell for use in concentrated sunlight[edit | edit source]
Abstract: The theoretical and experimental performance of an interdigitated back contact solar cell is described. This type of cell is shown to have significant advantages over a conventional solar cell design when used at high concentration levels, namely, reduced internal series resistance, nonsaturating open-circuit voltage, and an absence of shadowing by front surface contacting fingers. The results of a computer study are presented showing the effects of bulk lifetime, surface recombination velocity, device thickness, contact dimensions, and illumination intensity on the conversion efficiency and general device operation. Experimental results are presented for solar illumination intensities up to 28 W/cm2.
Abstract: Author(s) report the effects of concentrated sunlight on key photovoltaic parameters and stability of organic photovoltaics (OPV). Sunlight collected and concentrated outdoors was focused into an optical fiber and delivered onto a 1 cm2 bulk-heterojunction cell. Sunlight concentration C was varied gradually from 0.2 to 27 suns. Power conversion efficiency exhibited slow increase with C that was followed by saturation around 2% at C = 0.5–2.5 suns and subsequent strong reduction. Possible OPV applications in stationary solar concentrators (C ≤ 2 suns) are discussed. Finally, experiments at C = 55–58 suns demonstrated potential of our approach for accelerated studies of light induced mechanisms in the OPV degradation.
Abstract: Silicon nanowire-based solar cells on metal foil are described. The key benefits of such devices are discussed, followed by optical reflectance, current-voltage, and external quantum efficiency data for a cell design employing a thin amorphous silicon layer deposited on the nanowire array to form the p-n junction. A promising current density of ∼ 1.6 mA/cm2 for 1.8 cm2 cells was obtained, and a broad external quantum efficiency was measured with a maximum value of ∼ 12% at 690 nm. The optical reflectance of the silicon nanowire solar cells is reduced by one to two orders of magnitude compared to planar cells.
Abstract: An efficiency of 40.7% was measured and independently confirmed for a metamorphic three-junction GaInP/GaInAs/Ge cell under the standard spectrum for terrestrial concentrator solar cells at 240 suns (24.0 W/cm2, AM1.5D, low aerosol optical depth, 25 °C). This is the initial demonstration of a solar cell with over 40% efficiency, and is the highest solar conversion efficiency yet achieved for any type of photovoltaic device. Lattice-matched concentrator cells have now reached 40.1% efficiency. Electron-hole recombination mechanisms are analyzed in metamorphic GaxIn1−xAs and GaxIn1−xP materials, and fundamental power losses are quantified to identify paths to still higher efficiencies.
Abstract: The nanowire geometry provides potential advantages over planar waferbased or thin-ﬁlm solar cells in every step of the photoconversion process. These advantages include reduced reﬂection, extreme light trapping, improved band gap tuning, facile strain relaxation, and increased defect tolerance. These beneﬁts are not expected to increase the maximum efﬁciency above standard limits; instead, they reduce the quantity and quality of material necessary to approach those limits, allowing for substantial cost reductions. Additionally, nanowires provide opportunities to fabricate complex single-crystalline semiconductor devices directly on low-cost substrates andelectrodes such as aluminum foil, stainless steel, and conductive glass, addressing another major cost in current photovoltaic technology. This review describes nanowire solar cell synthesis and fabrication, important characterization techniques unique to nanowire systems, and advantages of the nanowire geometry.
Three-dimensional nanopillar-array photovoltaics on low-cost and flexible substrates[edit | edit source]
Abstract: Solar energy represents one of the most abundant and yet least harvested sources of renewable energy. In recent years, tremendous progress has been made in developing photovoltaics that can be potentially mass deployed Of particular interest to cost-effective solar cells is to use novel device structures and materials processing for enabling acceptable efficiencies. In this regard, here, Author(s) report the direct growth of highly regular, single-crystalline nanopillar arrays of optically active semiconductors on aluminium substrates that are then configured as solar-cell modules. As an example, Author(s) demonstrate a photovoltaic structure that incorporates three-dimensional, single-crystalline n-CdS nanopillars, embedded in polycrystalline thin films of p-CdTe, to enable high absorption of light and efficient collection of the carriers. Through experiments and modelling, Author(s) demonstrate the potency of this approach for enabling highly versatile solar modules on both rigid and flexible substrates with enhanced carrier collection efficiency arising from the geometric configuration of the nanopillars.
Abstract: Global environmental concerns and the escalating demand for energy, coupled with steady progress in renewable energy technologies, are opening up new opportunities for utilization of renewable energy resources. Solar energy is the most abundant, inexhaustible and clean of all the renewable energy resources till date. The power from sun intercepted by the earth is about 1.8 × 1011 MW, which is many times larger than the present rate of all the energy consumption. Photovoltaic technology is one of the finest ways to harness the solar power. This paper reviews the photovoltaic technology, its power generating capability, the different existing light absorbing materials used, its environmental aspect coupled with a variety of its applications. The different existing performance and reliability evaluation models, sizing and control, grid connection and distribution have also been discussed.
References[edit | edit source]
- H. Tong, H. Zhao, V. A. Handara, J. A. Herbsommer, and N. Tansu, “Analysis of thermoelectric characteristics of AlGaN and InGaN semiconductors,” Proceedings of SPIE, vol. 7211, no. 1, pp. 721103-721103-11, Feb. 2009
- B. N. Pantha, R. Dahal, J. Li, J. Y. Lin, H. X. Jiang, and G. Pomrenke, “Thermoelectric properties of InxGa1−xN alloys,” Applied Physics Letters, vol. 92, no. 4, pp. 042112-042112-3, Jan. 2008
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- J.-K. Ho et al., “Low-resistance ohmic contacts to p-type GaN achieved by the oxidation of Ni/Au films,” Journal of Applied Physics, vol. 86, no. 8, pp. 4491-4497, Oct. 1999
- M. D. Lammert and R. J. Schwartz, “The interdigitated back contact solar cell: A silicon solar cell for use in concentrated sunlight,” IEEE Transactions on Electron Devices, vol. 24, no. 4, pp. 337- 342, Apr. 1977
- T. Tromholt, E. A. Katz, B. Hirsch, A. Vossier, and F. C. Krebs, “Effects of concentrated sunlight on organic photovoltaics,” Applied Physics Letters, vol. 96, no. 7, pp. 073501-073501-3, Feb. 2010
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- R. R. King et al., “40% efficient metamorphic GaInP/GaInAs/Ge multijunction solar cells,” Applied Physics Letters, vol. 90, no. 18, pp. 183516-183516-3, May 2007
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- Z. Fan et al., “Three-dimensional nanopillar-array photovoltaics on low-cost and flexible substrates,” Nat Mater, vol. 8, no. 8, pp. 648-653, 2009