Electrical detection of Rabi oscillations in microcrystalline silicon thin-film solar cells

Abstract

The microscopic structure of light-activated paramagnetic conduction band tail states and their participation in spin-dependent hopping transport is studied in a microcrystalline silicon thin-film solar cell. Application of X- and S-band electrically detected magnetic resonance (EDMR) experiments in combination with numerical simulations of Rabi oscillations indicates that the spin-dependent process takes place between two neighbouring band tail states. For sufficiently high microwave (mw) power, two Rabi frequencies Ω₁ and Ω₂ = 2Ω₁ show up in the coherent EDMR signals. An analysis of their relative contributions to the Rabi traces suggests that the g-values of both spin partners are not correlated for the majority of the EDMR-active pairs. A small fraction of doublet pairs with similar g-values may explain the appearance of a larger Ω₂ contribution than predicted by the simulations.

Keywords:

• EDMR
• Rabi oscillations
• microcrystalline silicon
• solar cells

Acknowledgements

We are grateful to O. Astakhov and F. Finger (Forschungszentrum Jülich) for sample preparation as well as to K.-P. Dinse (FU Berlin), Alexander Schnegg and Klaus Lips (Helmholtz-Zentrum Berlin) for helpful discussions. Financial support from BMBF (EPR-Solar network project 03SF0328) is acknowledged.