Accelerated Stress Testing of Terrestrial Solar Cells

The results of a program to investigate the reliability characteristics of unencapsulated low-cost terrestrial solar cells using accelerated stress testing are presented. Four types of cells were investigated. Reliability (or parametric degradation) factors appropriate to the cell technologies and use conditions were studied and a schedule of accelerated stress tests was synthesized. An electrical measurement procedure capable of distinguishing small chanes in cell electrical parameters was established. A data analysis and management system was derived, and stress test fixturing and material flow procedures were set up after consideration was given to the number of cells to be stress tested and measured and the nature of the information to be obtained from the process. Based on both electrical parameters and metalization adherence strength, significant degradation was shown by some cell types in some stress tests. Other combinations of cell types and stress tests resulted in no detectable cell degradation. Analysis of the origins of the differences in degradation is continuing.