This PDF file contains the front matter associated with SPIE Proceedings Volume 7045, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.
The long-term performance data of copper indium diselenide (CIS) and gallium-alloyed CIS (CIGS) photovoltaic (PV)
modules are investigated to assess the reliability of this technology. We study and report on numerous PV modules
acquired from two manufacturers (A and B), deployed at NREL's outdoor test facility (OTF) in various configurations in
the field: some are free standing, loaded with a fixed resistance and periodically tested indoors at STC; other modules are
connected to data acquisition systems with their performance continuously monitored. Performance is characterized
using current-voltage (I-V) measurements obtained either at standard test conditions or under real-time monitoring
conditions: the power parameters plus other factors relating to quality like diode quality factors or series resistance are
analyzed for changes against time. Using standard diode analysis to determine the sources of degradation indicates that
CIS modules can exhibit between moderate and negligible degradation, with the dominant loss mode being fill factor
declines along with decreases in open-circuit voltage, for illumination intensities near 1-sun. At lower intensities, current
losses can appear appreciable. The real-time performance data also indicate that fill factor loss is the primary degradation
mode, generally as a result of increases in series resistance.
Recent investigations of rapid thermal processing (RTP) of thin films using an in-situ optical process control in
conjunction with in-situ energy-dispersive X-ray diffraction (EDXRD) are presented. The growth of Cu(In,Ga)(S,Se)2
layers by sulfurization or selenization of sputtered Cu-In-Ga precursor layers was realized by a heating ramp from room
temperature to temperatures between 500 and 550°C during which elemental sulfur or elemental selenium was
evaporated by radiative heating. White light scattered at the surface of the growing Cu(In,Ga)(S,Se)2 layers was
monitored by a CCD camera in order to record in-situ the changing optical properties of the films. EDXRD was used to
monitor the evolving structural properties of the growing films simultaneously. During the sulfurization and selenization
process the growing films pass through various phase transition which could be correlated with the white-light scattering
Detailed analysis of the time evolution of both signals (EDXRD and WLS) allowed to determine specific signatures in
the WLS signals indicating the influence of the process parameters on the growth process of Cu(In,Ga)(S,Se)2.
We have deposited textured ZnO:Al films over large areas using a reactive-environment hollow cathode sputtering (RE-HCS)
system developed in house, and have achieved excellent carrier mobilities (up to 49.5 cm2/Vs at a carrier
concentration of 4.42 x 1020/cm3). Both the electrical properties and optical properties (total transmission and haze) are
superior to those exhibited by commercially available SnO2:F. Using these textured ZnO:Al films, we have achieved an
a-Si:H solar cell efficiency boost of 8% relative to commercial SnO2:F superstrates which resulted from improvements
in all three PV parameters, namely Voc, Jsc, and FF. We have also determined the dependence of cell performance on the
degree of haze in the ZnO:Al films. Electrical, physical, and optical properties of ZnO:Al and SnO2:F, as determined by
four-point probe, Hall effect, SEM, AFM, ICP, transmission (total and diffuse), and work function measurements are
presented and correlated to the observed differences in a-Si solar cell performance. We have also developed a refractive
index matching layer that, when inserted between the TCO and the a-Si:H layers, resulted in an increase in Jsc of 3%.
Finally, we present some experiments on the effect of TCO type on nc-Si:H solar cell performance. From these
experiments, we confirmed that SnO2:F by itself is not a suitable TCO for nc-Si:H cells, but found that SnO2:F
overcoated with TiO2 followed by ZnO was the most effective superstrate for this type of cell.
Thin film photovoltaic applications typically require a front surface transparent conductive oxide (TCO). The most commercially successful TCO for photovoltaic applications has been fluorine doped tin oxide. Fluorine doped tin oxide is easily processed, mechanically durable, heat resistant, stable, and has controllable morphology. Tin oxide can be deposited during the glass manufacturing process, providing high performance coatings for an excellent value. Recent
developments in this field include conductivity shifting coatings, and multi-textured morphologies.
A Filtered Cathodic Vacuum Arc (FCVA) thin film deposition system has been used to create Al2O3/Al/Al2O3 trilayer
antireflection coatings on silicon. X-ray photoelectron spectroscopy was used to verify the stoichiometry of the
deposited alumina. The optical properties of the deposited Al2O3 and Al have been examined using variable angle
spectroscopic ellipsometry. The complex refractive index functions of the antireflection coating components were
determined. Optical thin film software was used to optimise the required thicknesses of each of the layers in order to
achieve minimum perpendicular reflection on silicon across the optical spectrum. The simulations showed that the
thickness of the Al layer was critical and the required layer thickness was less than 10 nm. Antireflection coatings with
various Al layer thicknesses were deposited and characterised. The microstructure of the coatings was examined, in
detail, using cross sectional transmission electron microscopy. Reflectance measurements on the deposited coatings
were also performed, with the optimised antireflection coating (with an Al layer thickness of 6 nm) achieving an average
reflectance of 4% on silicon over the optical spectrum. The FCVA deposited trilayers are mechanically robust, easy to
fabricate and exhibit high performance.
Spherical silicon photovoltaic devices are bonded to flexible substrates to produce light-weight flexible solar modules. In
order to maximize the conversion efficiency, the optical loss must be minimized. The concept of conventional anti
reflection coating (ARC) does not directly apply to the spherical device due to different geometry.
The optimum design of the ARC must maximize the optical power transmission from air to the Si crystal bulk. In
addition to the refractive index and the thickness of the ARC, the power distribution on the exposed spherical surface,
incidence angle dependent reflection, and multiple reflections at the spherical air-ARC and ARC-silicon interfaces also
influence the ARC design.
The effects of the spherical shape on the variations of the reflection are analyzed. It is shown that the optimum design is
essentially different from the conventional ARC with uniform quarter-wavelength thickness. It is required that the design
compensates the effect of variation of the incidence angle across the spherical surface. To achieve this, the thickness
should have a zenith-angle dependence. Chemical vapor deposition techniques can potentially be employed for the
deposition of the designed films.
In this work, we investigated the temperature dependence of wide bandgap hydrogenated amorphous silicon (a-Si:H)-based, hydrogenated amorphous silicon oxide (a-SiO:H)-based single-junction and hydrogenated protocrystalline silicon/hydrogenated microcrystalline silicon (pc-Si:H/μc-Si:H) double-junction solar cells in order to develop solar cells which are suitable for use in high temperature region. Photo J-V characteristics were measured under AM 1.5
illumination at ambient temperature in the range of 25-75 oC. We found that, the values of temperature coefficient for conversion efficiency (TC for η) of both single- and double-junction solar cells were inversely proportional to the initial
open-circuit voltage (Voc). In case of p-i-n single-junction solar cells, the typical pc-Si:H and pc-SiO:H solar cells
showed the lowest TC for η of -0.21 and -0.14%/oC, respectively. The smallest TC for η of pc-SiO:H solar cell was
attributed to the positive increase in TC for fill factor (FF). The TC for η of typical pc-Si:H/μc-Si:H double-junction
solar cells was around -0.35%/oC with initial η around 10-12%. Since high Voc pc-Si:H/μc-Si:H double-junction solar cells exhibit low temperature dependence and highly stable η against light soaking, they are promising for use in high
temperature regions. In addition, we conclude that solar cells which are suitable for use in high temperature region must be considered both high η with low temperature dependence.
The influence of the cathode electrode on the characteristics of pentacene/perylene derivatives based organic solar
cells was analysed by means of absorption, photoluminescence, and
X-ray spectroscopies. We report the characteristics
of a series of organic solar cells fabricated with Al, Ag, and Au electrodes for the interface between metals and organic
semiconductors, which play a central role in the physics of organic solar cells. Donor and acceptor layers of a solar cell
were pentacene and N,N'-dioctyl-3,4,9,10-perylenetetracarboxylic diimide (PTCDI-8C) and
N,N'-ditridecyl-3,4,9,10-perylene-tetracarboxylic diimide (PTCDI-13C) respectively. Two organic solar cells with
pentacene/PTCDI-8C and pentacene/PTCDI-13C heterojunctions as active layers were fabricated to compare the
influence of power conversion efficiency among perylene derivatives with various numbers of carbon molecules by
means of J-V measurements. Under the sunlight simulator with an AM1.5G filter and power of 100 mW/cm2, the solar
cells of the pentacene/PTCDI-13C heterojunction with the Ag cathode had J-V characteristics of short-circuit current density of 0.415 mA/cm2, open-circuit voltage of 0.413 V, fill factor of 0.55, and power conversion efficiency of 0.1%,
which were better than those of the pentacene/PTCDI-8C heterojunction. Moreover, according to the thin film analysis,
the PTCDI-13C thin film's excitons at the interface of the heterojunction for dissociation were more, and the probability
of radiative recombination of the electron-hole pair was less than for the PTCDI-8C. The PTCDI-13C thin-film
possessed better carrier mobility than PTCDI-8C. Therefore, we could conclude that the factors mentioned above are
keys to the pentacene/PTCDI-13C-based solar cells' better power conversion efficiency. The carrier transportation
mechanism of these solar cells is discussed clearly.
In this work, key properties of InxGa1-xN tandem solar cells (SCs) (single junction, double junctions and triple
junctions) were simulated by employing AMPS-1D software, including
I-V characteristic, efficiency, band structure,
built-in electric field etc. We compared the results of our simulation with the results of other theoretical
calculations published in the literature and analysed the causes of the differences among these results. We try to find
some useful information related to the important parameters of InGaN SCs, such as the band gap configuration and thickness selection. This work may help the progress in the preparation of the InGaN-based high efficiency solar cells.
Proc. SPIE 7045, The structural and material properties of CuInSe2 and Cu (In,Ga)Se2 prepared by selenization of stacks of metal and compound precursors by Se vapor for solar cell applications, 70450H (10 September 2008); doi: 10.1117/12.796381
CuInse2 films and related alloys were prepared by thermal evaporation of Cu, InSe and GaSe
compounds instead of elemental sources. Band gap tailoring in Cu(In,Ga)Se2 based solar cells is an
interesting path to improve their performance. In order to get comparable results solar cells with
Ga/(In+Ga) ratios x =0 and 0.3 were prepared, all with a simple
two-step sequential evaporation
process. The morphology of the resulting films grown at 550°C was characterized by the presence of
large facetted chalcopyrite grains, which are typical for device quality material. It is important to
note that absorber films with elemental gallium resulted in a significant decrease in the average grain
size of the film. The XRD diffraction pattern of a single-phase Cu(In,Ga)Se2 films depicts
diffraction peaks shift to higher 2θ values compared to that of pure CuInSe2 . The PL spectrum of
Cu(In,Ga)Se2 thin films also depicts the presence of the peak at higher energy that is attributed to the
incorporation of gallium into the chalcopyrite lattice. As the band gap of CIGS increases with
gallium content, desirable effects of producing higher open-circuit voltage and low-current density
devices were achieved. A corresponding increase in device efficiency with gallium content caused
by a higher fill factor was observed. The best results show passive area efficiencies of up to 10.2%
and open circuit voltage (Voc) up to 519 mV at a minimum band gap of 1.18eV.