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Theory and simulation of photogeneration and transport in Si-SiOx superlattice absorbers.

Aeberhard U - Nanoscale Res Lett (2011)

Bottom Line: Si-SiOx superlattices are among the candidates that have been proposed as high band gap absorber material in all-Si tandem solar cell devices.As a consequence of the finite number of wells and large built-in fields, the electronic spectrum can deviate considerably from the minibands of a regular superlattice.In this article, a quantum-kinetic theory based on the non-equilibrium Green's function formalism for an effective mass Hamiltonian is used for investigating photogeneration and transport in such devices for arbitrary geometry and operating conditions.

View Article: PubMed Central - HTML - PubMed

Affiliation: IEK-5: Photovoltaik, Forschungszentrum Jülich, D-52425 Jülich, Germany. u.aeberhard@fz-juelich.de.

ABSTRACT
Si-SiOx superlattices are among the candidates that have been proposed as high band gap absorber material in all-Si tandem solar cell devices. Owing to the large potential barriers for photoexited charge carriers, transport in these devices is restricted to quantum-confined superlattice states. As a consequence of the finite number of wells and large built-in fields, the electronic spectrum can deviate considerably from the minibands of a regular superlattice. In this article, a quantum-kinetic theory based on the non-equilibrium Green's function formalism for an effective mass Hamiltonian is used for investigating photogeneration and transport in such devices for arbitrary geometry and operating conditions. By including the coupling of electrons to both photons and phonons, the theory is able to provide a microscopic picture of indirect generation, carrier relaxation, and inter-well transport mechanisms beyond the ballistic regime.

No MeSH data available.


Related in: MedlinePlus

Spatially and energy-resolved charge carrier photogeneration rate in the quantum well region at short-circuit conditions and under monochromatic illumination with energy Eγ = 1.65 eV and intensity Iγ = 10 kW/m2.
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Figure 5: Spatially and energy-resolved charge carrier photogeneration rate in the quantum well region at short-circuit conditions and under monochromatic illumination with energy Eγ = 1.65 eV and intensity Iγ = 10 kW/m2.

Mentions: The spectral rate of carrier generation in the confined states under illumination with monochromatic light at photon energy Eγ = 1.65 eV and intensity Iγ = 10 kW/m2, is shown in Figure 5. At this photon energy, both the lowest and the second minibands are populated. The photocurrent originating in this excitation is shown in Figure 6. Current flows also in both first and second minibands, i.e., over the whole spectral range of generation, which means that relaxation due to scattering is not fast enough to confine transport to the band edge. However, transport of photocarriers is strongly affected by the inelastic interactions, and is the closest to the sequential tunneling regime.


Theory and simulation of photogeneration and transport in Si-SiOx superlattice absorbers.

Aeberhard U - Nanoscale Res Lett (2011)

Spatially and energy-resolved charge carrier photogeneration rate in the quantum well region at short-circuit conditions and under monochromatic illumination with energy Eγ = 1.65 eV and intensity Iγ = 10 kW/m2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211303&req=5

Figure 5: Spatially and energy-resolved charge carrier photogeneration rate in the quantum well region at short-circuit conditions and under monochromatic illumination with energy Eγ = 1.65 eV and intensity Iγ = 10 kW/m2.
Mentions: The spectral rate of carrier generation in the confined states under illumination with monochromatic light at photon energy Eγ = 1.65 eV and intensity Iγ = 10 kW/m2, is shown in Figure 5. At this photon energy, both the lowest and the second minibands are populated. The photocurrent originating in this excitation is shown in Figure 6. Current flows also in both first and second minibands, i.e., over the whole spectral range of generation, which means that relaxation due to scattering is not fast enough to confine transport to the band edge. However, transport of photocarriers is strongly affected by the inelastic interactions, and is the closest to the sequential tunneling regime.

Bottom Line: Si-SiOx superlattices are among the candidates that have been proposed as high band gap absorber material in all-Si tandem solar cell devices.As a consequence of the finite number of wells and large built-in fields, the electronic spectrum can deviate considerably from the minibands of a regular superlattice.In this article, a quantum-kinetic theory based on the non-equilibrium Green's function formalism for an effective mass Hamiltonian is used for investigating photogeneration and transport in such devices for arbitrary geometry and operating conditions.

View Article: PubMed Central - HTML - PubMed

Affiliation: IEK-5: Photovoltaik, Forschungszentrum Jülich, D-52425 Jülich, Germany. u.aeberhard@fz-juelich.de.

ABSTRACT
Si-SiOx superlattices are among the candidates that have been proposed as high band gap absorber material in all-Si tandem solar cell devices. Owing to the large potential barriers for photoexited charge carriers, transport in these devices is restricted to quantum-confined superlattice states. As a consequence of the finite number of wells and large built-in fields, the electronic spectrum can deviate considerably from the minibands of a regular superlattice. In this article, a quantum-kinetic theory based on the non-equilibrium Green's function formalism for an effective mass Hamiltonian is used for investigating photogeneration and transport in such devices for arbitrary geometry and operating conditions. By including the coupling of electrons to both photons and phonons, the theory is able to provide a microscopic picture of indirect generation, carrier relaxation, and inter-well transport mechanisms beyond the ballistic regime.

No MeSH data available.


Related in: MedlinePlus