Efficiency enhancement of ultrathin CIGS solar cells by optimal bandgap grading

Faiz Ahmad, Tom H. Anderson, Peter B. Monk, Akhlesh Lakhtakia

Research output: Contribution to journalArticle

Abstract

The power conversion efficiency of an ultrathin CuIn1−ξGaξSe2 (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.

Original languageEnglish (US)
Pages (from-to)6067-6078
Number of pages12
JournalApplied Optics
Volume58
Issue number22
DOIs
StatePublished - Aug 1 2019

Fingerprint

Solar cells
Energy gap
solar cells
augmentation
Open circuit voltage
open circuit voltage
Optoelectronic devices
Indium
Conversion efficiency
indium
inhomogeneity
inclusions

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics
  • Engineering (miscellaneous)
  • Electrical and Electronic Engineering

Cite this

Ahmad, Faiz ; Anderson, Tom H. ; Monk, Peter B. ; Lakhtakia, Akhlesh. / Efficiency enhancement of ultrathin CIGS solar cells by optimal bandgap grading. In: Applied Optics. 2019 ; Vol. 58, No. 22. pp. 6067-6078.
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Efficiency enhancement of ultrathin CIGS solar cells by optimal bandgap grading. / Ahmad, Faiz; Anderson, Tom H.; Monk, Peter B.; Lakhtakia, Akhlesh.

In: Applied Optics, Vol. 58, No. 22, 01.08.2019, p. 6067-6078.

Research output: Contribution to journalArticle

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