Process Development and Basic Studies of Electrochemically Deposited CdTe-Based Solar Cells: Annual Technical Report, Phase I; 15 May 1998 - 14 May 1999

The project describes long-term research and development issues related to polycrystalline thin-film solar cells. Our general research approach is based on combining activities aimed at improvement of cell performance and stability with activities aimed at increasing our fundamental understanding of the properties of materials making up the cells: CdTe, CdS, multi-layer back contact, andtransparent conducting oxide (TCO) front contact. We emphasize the relation between structural and electronic material properties and various processing procedures, as well as the microscopic mechanisms responsible for the cell performance and its degradation. Major results and conclusions of this project include:1) Stress tests of the cells under various stress conditions revealed conditionsproviding the most severe degrading of different cell parameters; 2) Consecutive stress testing under different bias revealed some reversible effects; 3) Preliminary analysis of the data obtained demonstrated a significant role of electromigration of the charged defects/impurities; 4) Some new approaches for the cell characterization and the data analysis were developed and checkedexperimentally; 5) New stress test experiments were planned for continued studies of degradation mechanisms.