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Varying Cadmium Telluride Growth Temperature During Deposition to Increase Solar Cell Reliability

National Renewable Energy Laboratory

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Technology Marketing Summary

Although most solar panels installed presently are composed of silicon, thin film Cadmium Telluride (CdTe) panels offer a number of advantages including lower degradation rate and better performance at high temperature, as well as lower overall material and energy usage during manufacturing. As silicon panels continue to drop in price, CdTe performance improvements are essential for the technology to remain competitive. The reliability of CdTe thin films continues to be a concern within the solar power industry, and researchers continue to search for ways to improve this limiting factor associated with use of CdTe thin films in solar cells.


Researchers at NREL have developed a method of growing CdTe solar cells with increased reliability by varying substrate growth during material deposition. The method involves preheating a substrate to remove moisture and then directly heating only the CdTe source, which indirectly heats the substrate upon which the CdTe is deposited. Therefore the first layer of CdTe is grown at a lower temperature than the final level, resulting in a smaller grain region near the junction. This more-compensated region limits diffusion of contaminants into the solar cell which results in a more reliable and stable cell. The devices fabricated using this method also demonstrate considerably higher minority carrier lifetimes relative to typical devices, resulting in enhanced performance.

  • Increased cell reliability
  • Increased minority carrier lifetimes
Applications and Industries
  • CdTe photovoltaics
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Patent 9,324,898
Varying cadmium telluride growth temperature during deposition to increase solar cell reliability
A method for forming thin films or layers of cadmium telluride (CdTe) for use in photovoltaic modules or solar cells. The method includes varying the substrate temperature during the growth of the CdTe layer by preheating a substrate (e.g., a substrate with a cadmium sulfide (CdS) heterojunction or layer) suspended over a CdTe source to remove moisture to a relatively low preheat temperature. Then, the method includes directly heating only the CdTe source, which in turn indirectly heats the substrate upon which the CdTe is deposited. The method improves the resulting CdTe solar cell reliability. The resulting microstructure exhibits a distinct grain size distribution such that the initial region is composed of smaller grains than the bulk region portion of the deposited CdTe. Resulting devices exhibit a behavior suggesting a more n-like CdTe material near the CdS heterojunction than devices grown with substrate temperatures held constant during CdTe deposition.
National Renewable Energy Laboratory 04/26/2016
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
REL ROI 12-65PrototypeAvailable09/07/201709/07/2017

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To: Bill Hadley<>