Observations of degraded CdS solar cells
Degraded CdS solar cell electrical characteristics and cell surface temperatures
Godlewski, M. P.↗
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Impurity profile and energy band diagram for the Cu sub 2 S-CdS heterojunction.
Impurity profiles and energy band diagram for cuprous sulfide-CdS heterojunction based on capacitance, Hall and electron microprobe measurements
Brandhorst, H. W., Jr.↗
Use of superconducting cavities to resolve carrier trapping effects in CdS.
Superconducting cavities for resolving optically induced changes in dielectric constant of CdS at 4.2 K
Hartwig, W. H.↗
The degradation of Cu2S-CdS thin film solar cells under simulated orbital conditions
Degradation of Cu2S-CdS thin film solar cells under simulated orbital conditions
Bernatowicz, D. T.↗
Light-induced modulation of broad-band optical absorption in CdS
Optical absorption due to imperfections in CdS by sensitive differential technique using laser excitation
Conway, E. J.↗
Long term tests of Cu2S-CdS thin film solar cells under simulated orbital conditions
Thin film Cu2S-CdS solar cells thermally cycled for 10,050 cycles under simulated orbital conditions
Clarke, D. R.↗
CdS solar cell development
Effects of manufacturing process variations on CdS solar cell performance and effect of temperature and time exposure during evaporation
Nastelin, H. E.↗
Photovoltage inversion effect and its application to semiconductor surface studies: CdS.
Experimental results on the surface states of the basal plane of CdS are presented and discussed in the light of a model of the photovoltage inversion effect. It is found that the surface states associated with this effect are in poor communication with the bulk and under normal conditions may require long periods of time to reach equilibrium. A combination of photovoltage inversion, photovoltage quenching, and photovoltage spectroscopy is believed to constitute a very effective tool for the study of surfaces of wide energy gap semiconductors.
Lagowski, J.↗
Electronic characteristics of 'real' CdS surfaces.
Photovoltage spectroscopy (including photovoltage inversion and photovoltage quenching) was used to determine the electronic characteristics of real (basal and prismatic) surfaces of CdS. In room atmosphere, surface states with the following positions were found in the cadmium surfaces: Ec - Et equal to 0.05, 0.4, and 0.8 eV, and Ev - Et equal to 0.83 eV. The same surface states were present in the sulfur surfaces, with the exception of those at Ec - Et equal to 0.4 eV. In the prismatic and unetched basal surfaces, states at Ec - Et equal to 1.1 eV were found in addition to all of those found on the cadmium surfaces.
Lagowski, J.↗
Surface piezoelectric effect in non-centrosymmetric semiconductors - CdS.
It was found that mechanical bending of CdS wafers with the (00.1) orientation causes pronounced changes in the contact potential difference. The changes were of the order of one volt. This effect was attributed to the polarization induced in the depletion layer by the mechanical stress. On this basis a model was developed which accounts for the experimental results.
Lagowski, J.↗
Heat treatment effects in Cu2S-CdS heterojunction photovoltaic cells
The optical and electronic properties of single crystal Cu2S-CdS photovoltaic cells were investigated. In these cells trapped charge near the interface which is manifested by a persistent increase in junction capacitance (the photocapacitance) plays a significant role in determining the carrier transport properties. It was found that the severe degradation in short-circuit current observed in heat-treated cells can be separated into two components: (1) a relatively small thermal component occurring on heat-treatment in the dark, and (2) a much larger degradation caused by exposure to light at room temperature. By a short additional heat-treatment above approximately 100 C the cell can be completely restored to its condition before the optically caused degradation with no effect on the depletion layer width.
Fahrenbruch, A. L.↗
Optical absorption components of light-modulated absorption spectrum of CdS
The amplitude and decay coefficient of light-induced modulation of absorption (LIMA) was measured as a function of wavelength from 535 to 850 nm for single-crystal CdS. The decay coefficient exhibited a discontinuous resonance at 710 nm which was due to the overlap and cancellation of two opposing absorption changes. A method was developed to separate these opposing absorption changes using the measured decay coefficients. The discrete-level-to-band energy for one absorption change was found to be 1.64 eV. An improved model was developed which contains two associated levels in the band gap separated by 0.32 eV.
Conway, E. J.↗
Very low cost thin film CdS-Cu2S solar cell development using chemical spraying
A chemical spray process for the production of thin film CdS-Cu2S solar cells is discussed that is projected to cost less than $60/kW in very large scale production. The average efficiency of these cells has been improved from less than 0.3% in 1971 about 4.5% at present. Further developments for the process are considered to raise the efficiency, and to attain long life stability.
Samara, G. A.↗
CdS thin film solar cells for terrestrial power
The development of very low cost long lived Cu2S/CdS thin film solar cells for large scale energy conversion is reported. Excellent evaporated metal grid patterns were obtained using a specially designed aperture mask. Vacuum evaporated gold and copper grids of 50 lines per inch and 1 micron thickness were adequate electrically for the fine mesh contacting grid. Real time roof top sunlight exposure tests of encapsulated CdS cells showed no loss in output after 5 months. Accelerated life testing of encapsulated cells showed no loss of output power after 6 months of 12 hour dark-12 hour AMI illumination cycles at 40 C, 60 C, 80 C and 100 C temperatures. However, the cells changed their basic parameters, such as series and shunt resistance and junction capacitance.
Shirland, F. A.↗
Insolation measurements with a portable CuS-CdS radiometer
Solar radiation measurements were carried out with a portable Cu2S-Cds radiometer. The measurements were found to be accurate to better than 5% (better than 3% when sophisticated metering is employed). Calibration to an Eppley precision pyranometer is discussed.
Windawi, H. M.↗
Rise kinetics of light-induced modulation of absorption for a CdS crystal
An experimental study has been made of the rise kinetics for changes in optical absorption in a single crystal of CdS which was bulk excited by pulsed laser light. The experimental data were compared to calculations from a simple model involving a bimolecular process. Experimental and calculated values agreed to within the experimental error and confirmed that light-induced modulation of absorption is a bimolecular process.
Long, E. R., Jr.↗
Surface photovoltage in exciton absorption range in CdS
The high resolution, intrinsic spectra of surface photovoltage are reported for semiconducting n-type CdS single crystals. At reduced temperatures (120-160 K) the spectra exhibit three sharp maxima due to A, B and C free exciton transitions. Energy positions of these lines and valence band parameters (spin-orbit and crystal field splittings) estimated from surface photovoltage are in good agreement with values obtained by other methods. The excitonic transitions are very sensitive to surface treatment, i.e. polishing, etching, background illumination and surface doping. The mechanism of direct interaction of free excitons with surface states is proposed to explain exciton lines in surface photovoltage.
Morawski, A.↗
MIS diode structure in As/+/ implanted CdS
Structure made by As implantation of carefully prepared high-conductivity CdS surfaces followed by Pt deposition and 450 C anneal display rectifying, although substantially different, I-V characteristics in the dark and during illumination with subband-gap light. Structures prepared in the same way on an unimplanted portion of the substrate have similar I-V characteristics, except that the forward turnover voltage for an illuminated unimplanted diode is much smaller than that for an implanted diode. It is suggested that the charge conduction in both structures is dominated by hole and/or electron tunneling through a metal-semiconductor potential barrier. The tunneling processes appear to be quite sensitive to subband-gap illumination, which causes the dramatic decreases of turnover voltages and apparent series resistances. The difference in turnover voltage appears to be caused by interface states between the Pt electrode and the implanted layer, which suggests a MIS model.
Hutchby, J. A.↗