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MM: Fachverband Metall- und Materialphysik
MM 9: Topical Session TEM III
MM 9.3: Talk
Monday, March 14, 2011, 16:45–17:00, IFW A
TEM studies of PbS-ZnS/ZnO quantum confinement structures for solar cells — •Peter G. Schindler1, Neil P. Dasgupta2, Orlando Trejo2, Christian Rentenberger1, Thomas Waitz1, Fritz B. Prinz2, and Hans-Peter Karnthaler1 — 1University of Vienna, Physics of Nanostructured Materials, Boltzmanngasse 5, 1090 Wien, Austria — 2Stanford University, Dept. of Mechanical Engineering, Stanford, CA 94305, USA
Research to maximize the efficiency of solar cells used for photovoltaic power generation is a timely issue. Si technology uses only a limited range of frequencies of the solar spectrum. To overcome this, quantum confinement solar cells give the opportunity for band gap engineering by quantum effects facilitated by dimensions in the nm range. We report on a transmission electron microscopy (TEM) study of layers of PbS and ZnS/ZnO deposited by atomic layer deposition. To prepare cross-section TEM samples the structures were glued together face to face to protect them. To achieve wedge shaped TEM foils with an extremely shallow angle the samples were mechanically polished and in a last step softly polished with Ar+ ions. The cross-sectioned multilayer quantum dot (QD) structure, its composition and morphology were investigated with different TEM techniques, e.g. high resolution TEM, and high angle annular dark field. The results are: The size of the QDs is in the range of the thickness of the layers which is about 2-5 nm. The QDs are faceted and either of small round shape or elongated along the layers. The range of size variations of the QDs increases with distance from the substrate resulting in the desired variation of band gaps.