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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.

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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.


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Band diagram of the p-i(SL)-n model system with the active quantum well absorber region.
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Figure 2: Band diagram of the p-i(SL)-n model system with the active quantum well absorber region.

Mentions: The model system under investigation is shown schematically in Figure 1. It consists of a set of four coupled quantum wells of six monolayer (ML) width with layers separated by oxide barriers of 3-ML thickness, embedded in the intrinsic region of a Si p-i-n diode. The thickness of the doped layers is 50 ML, while the total length of the i-region amounts to 154 ML. The monolayer thickness is half the Si lattice constant, i.e., Δ = 2.716 Å. The doping density is Nd = 1018 cm-3 for both electrons and holes. This composition and doping leads to the band diagram shown in Figure 2.


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

Aeberhard U - Nanoscale Res Lett (2011)

Band diagram of the p-i(SL)-n model system with the active quantum well absorber region.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Band diagram of the p-i(SL)-n model system with the active quantum well absorber region.
Mentions: The model system under investigation is shown schematically in Figure 1. It consists of a set of four coupled quantum wells of six monolayer (ML) width with layers separated by oxide barriers of 3-ML thickness, embedded in the intrinsic region of a Si p-i-n diode. The thickness of the doped layers is 50 ML, while the total length of the i-region amounts to 154 ML. The monolayer thickness is half the Si lattice constant, i.e., Δ = 2.716 Å. The doping density is Nd = 1018 cm-3 for both electrons and holes. This composition and doping leads to the band diagram shown in Figure 2.

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