A new approach to high-efficiency solar cells by band gap grading in Cu(In,Ga)Se2 chalcopyrite semiconductors

Dullweber, Thorsten; Anna, Gubarevich; Rau, Uwe; Schock, Hans‐Werner

doi:10.1016/s0927-0248(00)00274-9

Cited by 209 publications

(115 citation statements)

References 12 publications

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“…Whereas the copper-poor stoichiometry of the absorber surface is well known for the Shell Solar absorbers 16,17 and for other optimized CIGSSe absorbers, [26][27][28] to our knowledge this was found only once before at the back side of a CuInSe 2 absorber 12 , probably due to the difficulty of preparing suitable samples as mentioned above.…”

Section: -3mentioning

confidence: 77%

Spectroscopic investigation of the deeply buried Cu(In,Ga)(S,Se)2∕Mo interface in thin-film solar cells

Weinhardt

Fuchs

Peter

et al. 2006

The Journal of Chemical Physics

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The Cu͑In, Ga͒͑S,Se͒ 2 / Mo interface in thin-film solar cells has been investigated by surface-sensitive photoelectron spectroscopy, bulk-sensitive x-ray emission spectroscopy, and atomic force microscopy. It is possible to access this deeply buried interface by using a suitable lift-off technique, which allows us to investigate the back side of the absorber layer as well as the front side of the Mo back contact. We find a layer of Mo͑S,Se͒ 2 on the surface of the Mo back contact and a copper-poor stoichiometry at the back side of the Cu͑In, Ga͒͑S,Se͒ 2 absorber. Furthermore, we observe that the Na content at the Cu͑In, Ga͒͑S,Se͒ 2 / Mo interface as well as at the inner grain boundaries in the back contact region is significantly lower than at the absorber front surface.

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Section: -3mentioning

confidence: 77%

Spectroscopic investigation of the deeply buried Cu(In,Ga)(S,Se)2∕Mo interface in thin-film solar cells

Weinhardt

Fuchs

Peter

et al. 2006

The Journal of Chemical Physics

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“…A decrease in recombination would normally be expected to produce an increase in FF and V oc . However, in the new device, the deposition was ended with a small amount of In, without Ga. V oc is determined by Ga content in the space-charge region (SCR), including that at the surface of the CIGS; 12,13 therefore, we hypothesize that the method of reducing recombination presented here is achieved at the price of a slightly lower bandgap in a portion of the SCR, and thus no V oc increase is achieved. Minimum bandgap, which is the main determinant of J sc , occurs about 0Á5 mm into the film and is unchanged by near-surface variations.…”

Section: Device Characterizationmentioning

confidence: 99%

19·9%‐efficient ZnO/CdS/CuInGaSe² solar cell with 81·2% fill factor

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Egaas

et al. 2008

Progress in Photovoltaics

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“…[13][14][15] The effect of this internal offset at the GBs could be of similar importance as it is at the surface of the absorber, 33 whereas, there is ample experimental evidence for the Cu-poor surface layer 34,35 and its beneficial consequences for the performance of CIGS solar cells as long as the overall film composition is Cu-poor, 36 the question whether or not such a Cu-poor layer is a general positive feature of GBs in CIGS is still under discussion. [37][38][39][40] The present study concentrates on investigating the effect of such an internal band offset and on finding the conditions that have to be fulfilled if the Cu-poor layer should have a decisive beneficial effect on the performance of polycrystalline CIGS solar cells.…”

Section: A Excess Barrier Heightmentioning

confidence: 99%

Numerical simulation of carrier collection and recombination at grain boundaries in Cu(In,Ga)Se2 solar cells

Taretto

Rau

2008

Journal of Applied Physics

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Two-dimensional numerical device simulations investigate the influence of grain boundaries ͑GBs͒ on the performance of Cu͑In, Ga͒Se 2 solar cells. We find that the electronic activity of grain boundaries can reduce the efficiency of Cu͑In, Ga͒Se 2 solar cells from 20% to below 12% making proper passivation of GBs a primary requirement for high efficiency. Cell efficiencies larger than 19% require GB defect densities below 10 11 cm −2 . Also, an internal band offset in the valence band due to a Cu-poor region adjacent to the GBs could effectively passivate grain boundaries that are otherwise very recombination active. It is shown that such a barrier must be more than 300 meV high and at least 3 nm wide to virtually suppress all grain boundary recombination. Contrariwise, such a barrier represents an obstacle for hole transport reducing carrier collection across grain boundaries that are not perpendicular to the cell surface. We further find that inverted grain boundaries lead to an accumulation of the short circuit current along the grain boundary, which in certain situations enhances the total short circuit current. However, we do not find any beneficial effect of any type of grain boundaries on the overall cell efficiency.

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A new approach to high-efficiency solar cells by band gap grading in Cu(In,Ga)Se2 chalcopyrite semiconductors

Cited by 209 publications

References 12 publications

Spectroscopic investigation of the deeply buried Cu(In,Ga)(S,Se)2∕Mo interface in thin-film solar cells

Spectroscopic investigation of the deeply buried Cu(In,Ga)(S,Se)2∕Mo interface in thin-film solar cells

19·9%‐efficient ZnO/CdS/CuInGaSe² solar cell with 81·2% fill factor

Numerical simulation of carrier collection and recombination at grain boundaries in Cu(In,Ga)Se2 solar cells

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A new approach to high-efficiency solar cells by band gap grading in Cu(In,Ga)Se2 chalcopyrite semiconductors

Cited by 209 publications

References 12 publications

Spectroscopic investigation of the deeply buried Cu(In,Ga)(S,Se)2∕Mo interface in thin-film solar cells

Spectroscopic investigation of the deeply buried Cu(In,Ga)(S,Se)2∕Mo interface in thin-film solar cells

19·9%‐efficient ZnO/CdS/CuInGaSe2 solar cell with 81·2% fill factor

Numerical simulation of carrier collection and recombination at grain boundaries in Cu(In,Ga)Se2 solar cells

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Product

Resources

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19·9%‐efficient ZnO/CdS/CuInGaSe² solar cell with 81·2% fill factor