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HL: Fachverband Halbleiterphysik

HL 39: Photovoltaics II

HL 39.3: Vortrag

Mittwoch, 24. März 2010, 10:00–10:15, H3

Defect reduction in silicon nanocrystals by low-temperature annealing — •Sabrina Niesar¹, Nadine Erhard¹, Andre R. Stegner¹, Rui N. Pereira², Hartmut Wiggers³, Martin S. Brandt¹, and Martin Stutzmann¹ — ¹Walter Schottky Institut, Technische Universität München, 85748 Garching — ²University of Aveiro, 3810-193 Aveiro, Portugal — ³Institut für Verbrennung und Gasdynamik, Universität Duisburg-Essen, 47057 Duisburg

Due to the potential of low-cost solution processing, freestanding silicon nanocrystals (Si-ncs) are a promising base material for application e.g. in photovoltaics, thermoelectric and printable electronics. They can be synthesized in macroscopic amounts with diameters tunable between 4 and 50 nm by microwave-induced decomposition of silane in a low-pressure plasma reactor. In this work, we investigate different cost-efficient post-growth methods to reduce the number of silicon dangling bond defects (Si-dbs) which are a limiting factor for many electronic applications. Using electron paramagnetic resonance measurements, it is found that an etching step with hydrofluoric (HF) acid combined with a low-temperature vacuum annealing at 200°C leads to a reduction of the Si-dbs density by a factor of 10. Furthermore, conductivity measurements performed on thin Si-ncs films show that HF etching and annealing also improves the electronic properties. For highly doped Si-ncs, we observe a significant and persistent increase of the room-temperature conductivity. Moreover, current-voltage measurements on Si-ncs/organic semiconductor heterojunction solar cells will be presented.