Effect of grain boundaries in silicon on minority-carrier diffusion length and solar-cell efficiency

Daud, T.; Koliwad, K. M.; Allen, F. G.

doi:10.1063/1.90250

Cited by 40 publications

(8 citation statements)

References 2 publications

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“…Along with the minority-carrier lifetime, minority-carrier diffusion length is a measure by which to characterize absorber materials. To achieve higher efficiencies in a solar cell, a longer minority-carrier diffusion length is essential [75]. We evaluated those for BaSi2 determined a short minority-carrier diffusion length [19].…”

Section: Minority-carrier Diffusion Lengthmentioning

confidence: 99%

Exploring the potential of semiconducting BaSi₂for thin-film solar cell applications

Suemasu

Usami

2016

J. Phys. D: Appl. Phys.

114

106

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Semiconducting barium disilicide (BaSi2), which is composed of earth-abundant elements, has attractive features for thin-film solar cell applications; both a large absorption coefficient comparable to copper indium gallium diselenide and a minority-carrier diffusion length much larger than the grain size of BaSi2 can be used to improve solar cells properties. In this review article, we explore the potential of semiconducting BaSi2 films for thin-film solar cell applications. We start by describing its crystal and energy band structure, followed by discussing thin-film growth techniques and the optical and electrical properties of BaSi2 films. We used a first-principle calculation based on density-functional theory to calculate the position of the Fermi level to predict the carrier type of impurity-doped BaSi2 films using either a Group 13 or 15 element, and compare the calculated results with the experimental ones. Special attention was paid to the minority-carrier properties, such as minority-carrier lifetime, minority-carrier diffusion length, and surface passivation. The potential variations across the grain boundaries measured by Kelvin-probe force microscopy allowed us to detect a larger minority-carrier diffusion length in BaSi2 on Si(111) compared with in BaSi2 on Si(001). Finally, we demonstrate the operation of p-BaSi2/n-Si heterojunction solar cells and discuss prospects for future development.

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Section: Minority-carrier Diffusion Lengthmentioning

confidence: 99%

Exploring the potential of semiconducting BaSi₂for thin-film solar cell applications

Suemasu

Usami

2016

J. Phys. D: Appl. Phys.

114

106

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“…The minority carrier diffusion length, L, is one of the most important parameters directly affecting this conversion efficiency and is detrimentally decreased by carrier recombination at defects such as dislocations and grain boundaries (GBs). [4][5][6][7][8] For example, the photocurrent density increases as L increases in the case of crystalline Si; thus, higher g values can be expected to lead to larger L values. 9 Grain boundaries in poly-crystalline Si have been investigated using electron beam-induced current and Kelvin probe force microscopy techniques to determine if they act as recombination centers.…”

Section: Introductionmentioning

confidence: 99%

First-principles study of twin grain boundaries in epitaxial BaSi2 on Si(111)

Baba

Kohyama

Suemasu

2016

Journal of Applied Physics

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Epitaxial films of BaSi2 on Si(111) for solar cell applications possess three epitaxial variants and exhibit a minority carrier diffusion length (ca. 9.4 μm) much larger than the domain size (ca. 0.2 μm); thus, the domain boundaries (DBs) between the variants do not act as carrier recombination centers. In this work, transmission electron microscopy (TEM) was used to observe the atomic arrangements around the DBs in BaSi2 epitaxial films on Si(111), and the most stable atomic configuration was determined by first-principles calculations based on density functional theory to provide possible interface models. Bright-field TEM along the a-axis of BaSi2 revealed that each DB was a twin boundary between two different epitaxial variants, and that Ba(II) atoms form hexagons containing central Ba(I) atoms in both the bulk and DB regions. Four possible interface models containing Ba(I)-atom interface layers were constructed, each consistent with TEM observations and distinguished by the relationship between the Si tetrahedron arrays in the two domains adjacent across the interface. This study assessed the structural relaxation of initial interface models constructed from surface slabs terminated by Ba(I) atoms or from zigzag surface slabs terminated by Si tetrahedra and Ba(II) atoms. In these models, the interactions or relative positions between Si tetrahedra appear to dominate the relaxation behavior and DB energies. One of the four interface models whose relationship between first-neighboring Si tetrahedra across the interface was the same as that in the bulk was particularly stable, with a DB energy of 95 mJ/m2. There were no significant differences in the partial densities of states and band gaps between the bulk and DB regions, and it was therefore concluded that such DBs do not affect the minority carrier properties of BaSi2.

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“…The values of the EMC photovoltaic quantities are always more optimistic than the corresponding values computed by means of the 3D-model. The EMC short-circuit photocurrent can be greater than the computed photocurrent by about 7 %, whereas the EMC dark saturation current can be smaller by a factor of 2 [22]. The shift in the open circuit voltages is relatively small because of the logarithmic dependence of Voc on the currents, but the EMC conversion efficiency can be overestimated by about 1.5 point if the grain size is small with respect to the bulk diffusion length Ln (Fig.…”

Section: Base Doping Concentration Influence -mentioning

confidence: 92%

“…In polycrystalline silicon, an « effective diffusion length » is often defined in order to take into account the grain boundary recombination. By means of this concept of effective quantities, an « equivalent monocrystalline cell » (EMC) can be defined as a cell whose diffusion length would be equal to this theoretical effective diffusion length or to a measured one [22,23]. The photovoltaic properties of the polycrystalline cell are then assumed to be the same as those of the EMC.…”

Section: Base Doping Concentration Influence -mentioning

confidence: 99%

3D-Modelling of polycrystalline silicon solar cells

Dugas¹,

Oualid²

1987

Rev. Phys. Appl. (Paris)

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2014 Nous nous intéressons à l'influence des joints de grains sur les principaux paramètres qui caractérisent les photopiles en silicium polycristallin. Nous calculons la vitesse de recombinaison effective à l'aide d'une méthode auto-consistante qui tient compte de la courbure du quasi-niveau de Fermi des minoritaires dans la région de charge d'espace associée au joint et dans la région quasi neutre des grains. En nous basant sur cette étude, nous avons tracé à l'aide d'un modèle à 3 dimensions une série d'abaques qui permettent de prévoir les variations des propriétés photovoltaïques en fonction des grandeurs caractéristiques d'un matériau semiconducteur polycristallin : dimension g des grains, longueur de diffusion Ln et dopage NA des grains et vitesse de recombinaison interfaciale S aux joints de grains. Nous montrons que le rendement peut être augmenté en ajustant le dopage de la base des photopiles. Le dopage optimum est donné en fonction de la densité des états d'interface et de la dimension des grains. Enfin, nous définissons une longueur de diffusion effective dans un matériau polycristallin prenant en compte la recombinaison aux joints de grains.

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Effect of grain boundaries in silicon on minority-carrier diffusion length and solar-cell efficiency

Cited by 40 publications

References 2 publications

Exploring the potential of semiconducting BaSi₂for thin-film solar cell applications

Exploring the potential of semiconducting BaSi₂for thin-film solar cell applications

First-principles study of twin grain boundaries in epitaxial BaSi2 on Si(111)

3D-Modelling of polycrystalline silicon solar cells

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Effect of grain boundaries in silicon on minority-carrier diffusion length and solar-cell efficiency

Cited by 40 publications

References 2 publications

Exploring the potential of semiconducting BaSi2for thin-film solar cell applications

Exploring the potential of semiconducting BaSi2for thin-film solar cell applications

First-principles study of twin grain boundaries in epitaxial BaSi2 on Si(111)

3D-Modelling of polycrystalline silicon solar cells

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Exploring the potential of semiconducting BaSi₂for thin-film solar cell applications

Exploring the potential of semiconducting BaSi₂for thin-film solar cell applications