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Diamond like carbon (DLC) thin films were deposited on various substrates, such as, silicon, quartz and ITO substrates at low temperature (≪100 °C) by microwave (MW) surface-wave plasma (SWP) chemical vapor deposition (CVD), for solar cell application. The methane (CH4), ethylene (C2H4) and acetylene (C2H2) were used as carbon precursors, while argon was used as carrier gas. Nitrogen is used as dopant...
The electrical power available from a photovoltaic (PV) module can be simulated with the well-known and widely used [1–4] single diode equation. Five parameters must be known in the equation to determine the current-voltage relationship (I–V curve) for the module. These parameters can be obtained by fitting the experimental I–V curve at a fixed temperature and solar radiation for a small but representative...
Good surface passivation is necessary to achieve high efficiencies in silicon solar cells. One method is to epitaxially grow wide bandgap semiconductor materials on the silicon to act as a window layer that provides surface passivation and a minority carrier reflector. GaP and Si have a low lattice mismatch of 0.37% which is favorable for epitaxial growth while the growth of GaP on Si has the effect...
GaAs single junction solar cells were fabricated on epitaxial liftoff (ELO) 4:″ GaAs wafers. 1 cm2 single junction GaAs solar cells have been fabricated with a yield ≫80% across full 4″ ELO wafers. Photoluminescence studies of ELO GaAs wafers showed no evidence of residual strain in the layers as indicated by single peak at 870 nm at 300 K. Transmission electron microscopy studies of ELO solar cells...
The II–VI semiconductor cadmium selenide telluride CdSeTe was grown by MBE on silicon. The large lattice mismatch to the silicon was accommodated in smaller steps using a beryllium telluride - zinc telluride buffer layer. A CdTe film grown on this buffer had about three times narrower x-ray diffraction peak than a CdSe0.40Te0.60 alloy. Photojunction devices were formed into mesa structures with n+...
Two separate series of Mo thin films were deposited on Si/SiO2, and soda lime glass (SLG) substrates using direct-current planar magnetron sputtering, with a sputtering power density of 1.2 W/cm2. The working gas (Ar) pressure was varied from 0.6 mT to 16 mT to gain a better understanding of the effect of sputtering pressure on the morphology and porosity of the Mo thin films and the subsequent effect...
Modeling and fabrication of double layer MgF2/BN antireflection coatings have been undertaken. Minimal reflection losses (≪5%) over a wide range of the solar irradiance (1.1 to 3 eV) are realized for Si and GaAs. Dispersion (n,k) analyses of individual BN films using spectroscopic ellipsometry indicated a nearly constant index of refraction of ∼ 2.8 and a negligible transmission loss over the useful...
We have deposited ZnO at different substrate temperatures in a range of 120 ∼ 350 °C for back reflector (BR) with a structure of ZnO/Ag/Al/SS used in nano-crystalline silicon solar cells. AFM, XRD, SEM and optical transmittance have been employed to analyze the structure of ZnO films. It is found that the nano-crystalline solar cells on the back reflector with ZnO film deposited at 120 °C have a lower...
PV grid-connected systems are rich in nonlinear behaviors. Their operation depends on several factors such as radiation, switching algorithm and maximum power point tracking (MPPT) algorithm implemented in the grid-connected inverter which give rise to a variety of nonlinear behaviors and uncertainties. This paper proposes a passive impedance network as a model that can capture the system behaviors...
The question “Can a residential photovoltaic system provide all of the elements that would qualify it for consideration as a component of a retiree's investment portfolio?” was raised during the 4th World Conference on Photovoltaic Energy Conversion. To address this question one must consider the maturity of the technology, investment amount, derived revenue stream and overall risk. These factors...
Triple junction solar cells have been designed and fabricated for optimal performance under the Martian 60° latitude solar spectrum. Missions to Mar's polar latitudes will require cells optimized for the region's extreme conditions, including low solar intensity and temperature. Under a contract with JPL, Emcore's space-qualified satellite cell has been modified for optimal performance under the Martian...
We have attempted an in-line three-stage process for the deposition of CIGS (CuInGaSe2) absorber layers. The allowed growth area of CIGS deposition apparatus is 30 × 30 cm2, and the compositional uniformity and distribution of cell performance have been investigated. Large-size grains and band-grading typical for the three-stage process have been observed. The composition ratios and the performance...
Light weight, flexible, radiation hardened solar cells coatings are of interest for applications on satellite power generation owing to the potential advantages in terms of having higher specific power (lightweight), lower specific volume (flexible), and higher end-of-life power (superior radiation resistance), as compared to current state-of-the-art Ce-doped micro sheet solar cell coverglass. The...
The classical linear instability method (CLIM) of islanding prevention works by manipulating the control loop of a photovoltaic inverter such that when the utility disappears, right-half-plane poles appear, and the inverter becomes unstable, eventually leading to a shutdown due to abnormal voltage or frequency. The CLIM has been less well-studied than other methods, so in this work, a MATLAB/Simulink...
This paper reports the interim status in identifying and reviewing photovoltaic (PV) codes and standards (C&S) and related electrical activities for grid-connected, high-penetration PV systems with a focus on U.S. electric utility distribution grid interconnection. That includes identifying topics and concerns not yet in the scope of existing C&S documents, identifying C&S-related ongoing...
Silicon heterojunction solar cells have demonstrated high efficiencies through excellent surface passivation. However, the use of amorphous silicon (a-Si) in the structure raises the question of long term stability as a-Si solar cells suffer degradation due to the Staebler-Wronski effect. The stability of a-Si in terms of its ability to passivate silicon wafers is evaluated by measuring the minority...
Minority carrier lifetime and Suns-Voc measurements are well-accepted methods for characterization of solar cell devices. We use these methods, with an instrument from Sinton Consulting, as we fabricate and optimize state-of-the-art all hot-wire chemical vapor deposition (HWCVD) silicon heterojunction (SHJ) devices. For double-sided SHJ devices, lifetime measurements were performed immediately after...
Silicon nanowire carpets were grown from gold nanotemplates by the Vapor Liquid Solid (VLS) process. As substrates silicon wafers, laser crystallized silicon thin films on glass, or TCO on glass were used. The Au nanotemplates act, in a thermal CVD process, as a catalyst to decompose silane at about 500°C. The result is a carpet formed of perfect single crystalline nanowires several 10 to 200 nm in...
Co-sputtering of Cu and In leads to rough Cu-In layers with a bi-layer structure of the surface in which island-type crystals were formed in a small-crystalline matrix layer. The elemental composition of the island- type crystals corresponds to the compound CuIn2 and the matrix area consists of the copper-rich Cu11In9 phase. The formation of α-CuInSe2 was initiated at 300°C and resulted in films with...
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