A search for degradation mechanisms of CdTe/CdS solar cells

Book · Tue Dec 31 04:00:00 EST 1996

OSTI ID:417692

Meyers, P V ^[1]; Asher, S; Al-Jassim, M M ^[2]

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1. Univ. of Delaware, Newark, DE (United States). Inst. of Energy Conversion
2. NREL, Golden, CO (United States)

CdTe/CdS solar cells have demonstrated stability over thousands of hours of field testing, but have not yet established the same track record for reliability achieved by crystalline Si PV modules. In order to identify potential degradation mechanisms, this paper describes a series of experiments in which CdTe/CdS solar cells are subjected to combinations of temperature, voltage and illumination levels intended to stress the devices beyond levels which would be experienced in the field. During this process the devices display decreases in Voc and FF which are tentatively attributed to chemical changes at the low resistance contact to the CdTe and to changes in the electrical transport properties of the CdTe. Two thermally activated effects were observed depending upon stress bias. Reverse bias appears to degrade bulk CdTe electrical properties while forward bias strengthens a reverse diode which most likely is located at the back contact. Chemical analysis of the back contact region of the devices using XPS reveals strong oxide peaks in all stressed samples. Evidence of Cd diffusion into the Mo contacts is observed by SIMS and Auger. Mo diffusion into the CdTe is promoted by reverse bias stressing. Cu migration consistent with positively charged ions was indicated by SIMS.

• Sponsoring Organization: National Renewable Energy Lab., Golden, CO (United States)
• OSTI ID: 417692
• Report Number(s): CONF-960401--; ISBN 1-55899-329-0
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
AUGER ELECTRON SPECTROSCOPY
CADMIUM SULFIDE SOLAR CELLS
CADMIUM TELLURIDE SOLAR CELLS
CURRENT DENSITY
ELECTRIC CONTACTS
ELECTRIC POTENTIAL
EXPERIMENTAL DATA
FILL FACTORS
GLASS
ILLUMINANCE
ION MICROPROBE ANALYSIS
MASS SPECTROSCOPY
OXIDATION
PERFORMANCE
STRESSES
TEMPERATURE DEPENDENCE
TIN OXIDES
X-RAY SPECTROSCOPY