The roles of ZnTe buffer layers on CdTe solar cell performance
- Colorado School of Mines, Golden, CO (United States)
- Loughborough Univ., Leicestershire (United Kingdom)
- Colorado School of Mines, Golden, CO (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States)
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
The use of ZnTe buffer layers at the back contact of CdTe solar cells has been credited with contributing to recent improvements in both champion cell efficiency and module stability. To better understand the controlling physical and chemical phenomena, high resolution transmission electron microscopy (HR-TEM) and atom probe tomography (APT) were used to study the evolution of the back contact region during rapid thermal processing (RTP) of this layer. After activation the ZnTe layer, initially nanocrystalline and homogenous, transforms into a bilayer structure consisting of a disordered region in contact with CdTe characterized by significant Cd–Zn interdiffusion, and a nanocrystalline layer that shows evidence of grain growth and twin formation. Copper, co-evaporated uniformly within ZnTe, is found to dramatically segregate and aggregate after RTP, either collecting near the ZnTe|Au interface or forming CuxTe clusters in the CdTe layer at defects or grain boundaries near the interface. Analysis of TEM images revealed that Zn accumulates at the edge of these clusters, and three-dimensional APT images confirmed that these are core–shell nanostructures consisting of Cu1.4Te clusters encased in Zn. These changes in morphology and composition are related to cell performance and stability.
- Research Organization:
- Stanford Univ., CA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
- Grant/Contract Number:
- EE0004946; AC36-08GO28308
- OSTI ID:
- 1579808
- Alternate ID(s):
- OSTI ID: 1359875
- Journal Information:
- Solar Energy Materials and Solar Cells, Vol. 147, Issue C; ISSN 0927-0248
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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