Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Efficiency enhancement of ultrathin CIGS solar cells by optimal bandgap
  grading   The power conversion efficiency of an ultrathin CIGS solar cell was maximized
using a coupled optoelectronic model to determine the optimal bandgap grading
of the nonhomogeneous CIGS layer in the thickness direction. The bandgap of the
CIGS layer was either sinusoidally or linearly graded, and the solar cell was
modeled to have a metallic backreflector corrugated periodically along a fixed
direction in the plane. The model predicts that specially tailored bandgap
grading can significantly improve the efficiency, with much smaller
improvements due to the periodic corrugations. An efficiency of 27.7% with the
conventional 2200-nm-thick CIGS layer is predicted with sinusoidal bandgap
grading, in comparison to 22% efficiency obtained experimentally with
homogeneous bandgap. Furthermore, the inclusion of sinusoidal grading increases
the predicted efficiency to 22.89% with just a 600-nm-thick CIGS layer. These
high efficiencies arise due to a large electron-hole-pair generation rate in
the narrow-bandgap regions and the elevation of the open-circuit voltage due to
a wider bandgap in the region toward the front surface of the CIGS layer. Thus,
bandgap nonhomogeneity, in conjunction with periodic corrugation of the
backreflector, can be effective in realizing ultrathin CIGS solar cells that
can help overcome the scarcity of indium.

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The categories of this paper are: adap-org
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: bayes-an
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The categories of this paper are: ao-sci
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The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
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The categories of this paper are: acc-phys
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The categories of this paper are: nlin
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: math-ph