Cu from the back contact of a polycrystalline CdS/CdTe solar cell does more than assist in forming a low-resistance contact.

Angular dependence of x-ray fluorescence technique has been applied to the study of atomic density profile in composite systems. This method is shown to be useful for probing the microstructures and intermixing of constituent elements in layer-structured photovoltaic materials.

This paper is intended to be an overview of some of the challenges that must be overcome when characterizing amourphous-silicon solar cell devices by the secondary ion mass spectrometry (SIMS) technique.

A novel alloy, BGaInAs, may prove useful in high-efficiency III-V multijunction solar cells.

Direct mineral carbonation by an ex-situ process in an aqueous system has been investigated over the past two years. The process utilizes a slurry of water mixed with a magnesium silicate mineral, such as olivine [forsterite end member (Mg2SiO4)], or serpentine [Mg3Si2O5(OH)4]. This slurry is reacted with sub- or supercritical carbon dioxide (CO2) to produce magnesite (MgCO3). The CO2 is dissolved in water to form carbonic acid (H2CO3), which dissociates to H+ and HCO3-. The H+ ion hydrolyzes the mineral, liberating Mg2+ cations which react with the bicarbonate to form the solid carbonate. Results of the baseline tests, conducted on ground products of the natural minerals, have demonstrated that the kinetics of the reaction are slow at ambient temperature (22 C) and subcritical CO2 pressures (below 73 atm). However, at elevated temperature and pressure, coupled with continuous stirring of the slurry and gas dispersion within the water column, significant conversion to the carbonate occurs. Extent of reaction is roughly 90% within 24 hours, at 185 C and partial pressure of CO2 (PCO2) of 115 atm. Heat pretreatment of the serpentine, coupled with bicarbonate and salt additions to the solution, improve reaction kinetics, resulting in an extent of reaction of roughly …

The performance of CdS/CdTe solar cells is strongly impacted by the process used to grow the CdS layer. CdS films grown by chemical-bath deposition (CBD) exhibit lower sublimation (CSS).

Following a proposal by BP Solarex to modify the standard module qualification sequence, we performed a forward-biased themal cycling on three types of commercial modules to evaluate the procedure. The total number of thermal cycles was doubled to 400 and maximum power measurements were made every 50 cycles.

We have studied deep impurity levels of CdTe/CdS solar cells by capacitance-voltage (C-V), deep-level transient spectroscopy (DLTS) and time-resolved photoluminescence (TRPL).

Energy efficiency maximizes the value of photovoltaics (PV) in buildings systems. A fixed-sizre PV system will offset a much larger part of the electrical load in an energy-efficient building than in a building whose energy design has not been optimized.

The paper briefly summarizes the results from several accelerated exposure tests (AET) studies. Causes responsible for the photothermal instability of the encapsulated Si solar cells appear to be multiple and complex.

We increase the deposition rate of growing hydrogenated amorphous-silicon (a-Si:H) by the hot-wire chemical vapor depositon (HWCVD) technique by adding filaments (two) and decreasing the filament(s) to substrate distance.

Status results are presented for the Outdoor Accelerated-Weathering Tracking System (OATS) first study on photovoltaic (PV) modules. Studies began in November 1997 on pairs of commercially available crystalline silicon and amorphous silicon (a-Si) PV modules kept at constant resistive load.

Our recent silicon photovoltaic (PV) materials research activities are summarized.

Water and CO(2) uptake in CdCl(2) powder precursors was investigated using thermogravimetric analysis/Fourier transform infrared spectroscopy (TGA/FTIR). Exposure of powders under ambient conditions shows that a steady-state hydration level near 9% (by weight) is achieved after brief exposure to room air.

Fermi National Accelerator Laboratory (Fermilab), a high-energy physics laboratory operated by the Universities Research Association for the US Department of Energy, is developing plans for the construction of accelerator tunnels. The accelerator designs vary as a function of particles accelerated, technologies used and energies targeted. However, all accelerators require the excavation of long tunnels, up to 700 km in length, and tunnel costs represent a major portion of project budgets. This paper documents the findings of two studies undertaken to identify tunnel cost-drivers and outlines steps taken to initiate the ''value engineering'' of the tunnels.

We study the amorphous to microcrystalline silicon films made at three laboratories by using Raman, photoluminescence- and optical-abosrption spectroscopies.

This paper summarizes several studies analyzing consumer incentives for the grid-tied domestic photovoltaic (PV) market.

Structural studies using transmission electron microscopy have been made on 1-eV band-gap materials, lattice-matched to GaAs and Ge substrates, grown by metal-organic vapor-phase epitaxy for use in multijunction, high-efficiency solar cells.

Efficient hydrogenated amorphous silicon (a-Si:H) nip solar cells have been fabricated with all doped and undoped a-Si:H layers deposited by hot-wire chemical vapor deposition (HWCVD). The total deposition time of all layers, except the top ITO-contact, is less than 4 minutes.

This paper describes the needs, reasoning, approaches, and technical details to establish a practical accelerated weathering test (AWT) protocol for indoor testing of the photothermal stability of encapsulation materials and encapsulated solar cells and minimodules.

There are several production disadvantages inherent in the conventional SnO(2)/CdS/CdTe manufacturing processes. In this paper, we report a novel manufacturing process for fabrication of polycrystalline Cd(2)SnO(4)/Zn(2)/SnO(4)/CdS/CdTe thin-film solar cells that yielded a CdS/CdTe device with an NREL-confirmed efficiency of 14.0%.

The National Renewable Energy Laboratory (NREL) Photovoltiac Radiometric Measurements Task ddresses the impact of solar and optical radiation on photovoltaic (PV) devices. The task maintains spectral and broadband calibration capability directly traceable to the National Institute of Standards and Technology (NIST) and the World Radiometric Reference (WRR) of the World Meteorological Organization (WMO).

The residual stress, resistance, orientation, and microstructure of sputtered Mo films were studied as a function of varied-deposition power and pressure.

We demonstrated the feasibility of analyzing cross sections of thin-film CdTe/CdS and CIGS/CdS solar cells using atomic force microscopy (AFM).