High-Efficiency Polycrystalline CdS/CdTe Solar Cells on Buffered Commercial TCO-Coated Glass

• Published in: Journal of electronic materials 2012-10, Vol.41 (10), p.2833-2837
• Main Authors: Colegrove, E., Banai, R., Blissett, C., Buurma, C., Ellsworth, J., Morley, M., Barnes, S., Gilmore, C., Bergeson, J. D., Dhere, R., Scott, M., Gessert, T., Sivananthan, Siva
• Format: Article
• Language: English
• Subjects: Applied sciences; Buffer layers; Cadmium sulfides; Cadmium telluride; Cadmium tellurides; Characterization and Evaluation of Materials; Chemistry and Materials Science; Commercial spacecraft; Cross-disciplinary physics: materials science; rheology; Current density; Deposition by sputtering; Electronics; Electronics and Microelectronics; Energy; Exact sciences and technology; Glass; Instrumentation; Materials; Materials Science; Methods of deposition of films and coatings; film growth and epitaxy; Natural energy; Optical and Electronic Materials; Photovoltaic cells; Photovoltaic conversion; Physics; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Solid State Physics; Vapor phase epitaxy; growth from vapor phase
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-012-2100-z

Multiple polycrystalline CdS/CdTe solar cells with efficiencies greater than 15% were produced on buffered, commercially available Pilkington TEC Glass at EPIR Technologies, Inc. (EPIR, Bolingbrook, IL) and verified by the National Renewable Energy Laboratory (NREL). n -CdS and p -CdTe were grown by chemical bath deposition (CBD) and close space sublimation, respectively. Samples with sputter-deposited CdS were also investigated. Initial results indicate that this is a viable dry-process alternative to CBD for production-scale processing. Published results for polycrystalline CdS/CdTe solar cells with high efficiencies are typically based on cells using research-grade transparent conducting oxides (TCOs) requiring high-temperature processing inconducive to low-cost manufacturing. EPIR’s results for cells on commercial glass were obtained by implementing a high-resistivity SnO 2 buffer layer and by optimizing the CdS window layer thickness. The high-resistivity buffer layer prevents the formation of CdTe-TCO junctions, thereby maintaining a high open-circuit voltage and fill factor, whereas using a thin CdS layer reduces absorption losses and improves the short-circuit current density. EPIR’s best device demonstrated an NREL-verified efficiency of 15.3%. The mean efficiency of hundreds of cells produced with a buffer layer between December 2010 and June 2011 is 14.4%. Quantum efficiency results are presented to demonstrate EPIR’s progress toward NREL’s best-published results.