Doping profiles in CdTe/CdS thin film solar cells

• Published in: Thin solid films Vol. 515; no. 15; pp. 6175 - 6178
• Main Authors: Reislöhner, U., Hädrich, M., Lorenz, N., Metzner, H., Witthuhn, W.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 31-05-2007; Elsevier Science
• Subjects: Admittance spectroscopy; Applied sciences; CdTe; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; C–V profiling; Defects and impurities: doping, implantation, distribution, concentration, etc; DLTS; Doping; Energy; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Natural energy; Other semiconductors; Photovoltaic conversion; Physics; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Specific materials; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Thin films; Vapor phase epitaxy; growth from vapor phase; Solar cells; Thin films; C–V profiling; Admittance spectroscopy; Doping; DLTS; CdTe; Temperature dependence; Digital simulation; Cadmium sulfides; Doping profiles; Indium additions; Capacitance measurement; C-V profiling; CV characteristic; Vapor deposition; Quantity ratio; II-VI semiconductors; Thin film devices; Cadmium tellurides; Depth profiles
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2006.12.057

CdS/CdTe thin film solar cells showing comparable properties as commercial cells have been prepared by close space sublimation (CSS) in our own laboratory. We characterised the cells by capacitance–voltage profiling (C–V), thermal admittance spectroscopy (TAS), and thermally stimulated capacitance measurements (TSCAP). The doping profiles of the CdTe layer obtained by C–V measurements confirm the well known rise in dopant concentration with increasing depth if the usual evaluation procedure is employed. However, the TAS and TSCAP measurements reveal deep acceptors in the CdTe layer with a large concentration exceeding that of the shallow dopants. Under these conditions, C–V measurements are shown to yield an apparently rising dopant concentration even for homogeneous doping. A combined simulation of doping profiles measured at different temperatures using a fixed and uniform shallow and deep doping fits well to measured doping concentration. These results indicate how to get reliable information on the shallow dopant concentration.