Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 39: Photovoltaics: Chalcopyrites I

HL 39.5: Talk

Tuesday, March 15, 2011, 14:30–14:45, FOE Anorg

Investigation of the initial interface formation between CuInSe2 (112) and ZnO grown by ALD — •Eike Janocha and Christian Pettenkofer — Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Deutschland

The interface between a solar cell absorber and its transparent conductive oxide (TCO) defines the electrical properties and thus the efficiency of chalcopyrite solar cells. Since large conduction band offsets lower the solar cell photocurrent usually a CdS buffer layer is deposited by chemical bath deposition (CBD) between chalcopyrite absorber and TCO. Due to its toxicity and the interruption of the in-line production process by CBD an alternative buffer layer material would be advantageous.

To improve the efficiencies of chalcopyrite solar cells a detailed understanding of the electronic band structure between absorber and TCO is necessary. Therefore, we investigated a model system of a single crystalline CuInSe2 absorber material grown in the technological important (112) orientation by molecular beam epitaxy and an epitaxial ZnO TCO grown layer-by-layer via atomic layer deposition (ALD). ALD is known for being a deposition technique allowing the growth of a single monolayer due to its self-limiting growth characteristics.

In situ characterization of the initial growth has been performed after each ZnO deposition step by photoelectron spectroscopies (XPS/UPS/SR-PES) in an UHV growth and analysis system resulting in a detailed view of the interface formation and binding characteristics of the involved elements.