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HL: Halbleiterphysik
HL 27: Poster II: SiC (1-7), Ultrakurzzeitdynamik (8-15), Halbleiterlaser (16-20), GaN (21-38), III-V Halbleiter (39-56), Photovoltaik (57-64), Störstellen (65-68), Tern
äre Halbleiter (69-70)
HL 27.57: Poster
Wednesday, March 29, 2000, 14:00–19:00, A
Theoretical Study of Buffer Layer Effect on Open Circuit Voltage in Solar Cells — •Gottfried Heinrich Bauer — Fachbereich Physik, C.v.O. Universität, D-26111 Oldenburg
The open circuit voltage Voc in solar cells can be formulated by
splitting of Quasi-Fermi levels via Boltzmann approximation for
minority carrier concentration in steady state under photo excitation.
Since large absorption coefficients providing large excess minority
densities are accompanied by short distances to regimes with high
recombination velocities as well, such as the light entrance surface,
the introduction of buffer/passivation layers for the prevention of
minority motion towards low life time regimes is a common
approach.
We have theoretically studied and numerically simulated the influence
of 3 types of buffer layers on minorizy darrier concentration that
has been translated into Voc:
- buffer /passivation layers with reduced diffusion length
i) due to drop in life time;
ii) due to decrease in mobility/diffusion constant;
- buffer layers preventing minority diffusion/motion to the surface,
and allowing for undisturbed majority transport.
We discuss our results in terms of departures of Voc in buffered
cells from un-buffered ones and need in chemical potential for
carrier motion accross these regions.