Regensburg 2007 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 5: Photovoltaic
HL 5.8: Talk
Monday, March 26, 2007, 12:45–13:00, H14
Electrical Detection of Spin Coherence in Microcrystalline pin Solar Cells — •Jan Behrends1, Christoph Boehme1,2, Stefan Haas3, Bernd Rech1,3, and Klaus Lips1 — 1Hahn-Meitner-Institut Berlin, Abt. Silizium-Photovoltaik, Berlin, Germany — 2Department of Physics, University of Utah, Salt Lake City, UT, USA — 3Institute of Photovoltaics, Forschungszentrum Jülich, Jülich, Germany
Defects in the band gap of hydrogenated microcrystalline silicon (µc-Si:H) pin solar cells, even at low concentrations, can act as recombination centres and thus, they can influence the electronic properties of the device significantly. A powerful technique to investigate these recombination processes is pulsed electrically detected magnetic resonance (pEDMR). This method is based on transient photocurrent measurements after varying specific recombination or transport rates and reveals information about the microscopic mechanisms of recombination and transport that involve paramagnetic states. In this study we report on the application of pEDMR on state-of-the-art µc-Si:H pin solar cells prepared on ZnO coated glass. An adapted contact structure allows the observation of Rabi oscillations in the photocurrent at low temperatures (T=10K) reflecting coherent spin motion. The coherence time is found to be on the order of several hundred nanoseconds and is determined by recombination. A Fourier analysis of the observed Rabi oscillations allows a distinction between the involved recombination processes. A discussion on the different recombination mechanisms in µc-Si:H cells will be given.