Analysis of internal quantum efficiency in double-graded bandgap solar cells including sub-bandgap absorption

Troviano, M.; Taretto, K.

doi:10.1016/j.solmat.2010.10.028

Cited by 64 publications

(31 citation statements)

References 17 publications

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“…Given that EQE ¼ 84% at 532 nm, the absorber thickness is 2.5 lm, and assuming l p /l n ( 1, we evaluate L n to 3 lm, which is above reported value from EQE measurements. 12 Our results show that the resistance modulation is sufficiently important to decrease the series resistance by more than one order of magnitude in the explored concentration range. Maximum efficiencies at concentration ratios $1000 would require improved R c , now limited by the contact of the probe on Au.…”

mentioning

confidence: 66%

Microscale solar cells for high concentration on polycrystalline Cu(In,Ga)Se2 thin films

Paire

Lombez

Péré‐Laperne

et al. 2011

Applied Physics Letters

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International audienceWe report high concentration experiments on polycrystalline thin ﬁlm solar cells. High level regime is reached, thanks to the micrometric scale of the Cu(In,Ga)Se 2 cells, which strongly decreases resistive losses. A 4% absolute efﬁciency increase is obtained at a concentration of x120, and current densities as high as 100 A/cm² can be measured. These results show that the use of polycrystalline thin ﬁlms under high concentration is possible, with important technological consequences

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mentioning

confidence: 66%

Microscale solar cells for high concentration on polycrystalline Cu(In,Ga)Se2 thin films

Paire

Lombez

Péré‐Laperne

et al. 2011

Applied Physics Letters

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“…8,9 Especially the grading parameters within the space charge region (towards the front) seem to be critical. 7,8,11 Thereby, the extension in depth of the space charge region in Cu(In,Ga)Se 2 absorbers lies in a depth range of a few hundred nanometers, 9,17 where under solar cell operation, most of the photoexcited carriers are generated. Table II shows the characteristic PV parameters of devices made from absorber layers that have been deposited in the same deposition runs as the samples for the depth profile analyses.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, an increasing gallium content towards the molybdenum back contact is expected to enhance carrier collection and to decrease recombination via asymmetric diffusion, repelling electrons from the Cu(In,Ga)Se 2 /Mo interface. [5][6][7][8][9][10] The combination of a gallium grading towards the front and the back interfaces is commonly referred to as double grading. In general, a double grading within a Cu(In, Ga)Se 2 thin film can be achieved via the standard three-stage co-evaporation growth process.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, AXES provides information about the depth dependent gallium content in a depth range of the space charge region, which extends only a few hundred nanometers into the bulk. 9,17 In this depth range, most of the photoexcited carriers are generated and spatially separated under solar cell operation. Therefore, compositional gallium gradients are here of particular interest.…”

Section: Introductionmentioning

confidence: 99%

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Gallium gradients in chalcopyrite thin films: Depth profile analyses of films grown at different temperatures

Mönig

Kaufmann

Fischer

et al. 2011

Journal of Applied Physics

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Cu(In,Ga)Se 2 films are used as absorber layers in chalcopyrite thin film solar cells. As the gallium concentration in the absorber can be used to control the band gap, there have been many efforts to vary the gallium concentration in depth to gain an optimum balance of light absorption, carrier collection, and recombination at different depths of the absorber film, leading to improved quantum efficiency. In this study, we investigate the effect of the maximum substrate temperature during film growth on the depth dependent gallium concentration. For the in-depth gallium concentration analyses, we use two techniques, covering complementary depth ranges. Angle dependent soft x-ray emission spectroscopy provides access to information depths between 20 and 470 nm, which covers the depth range of the space charge region, where most of the photoexcited carriers are generated. Therefore, this depth range is of particular interest. To complement this investigation we use secondary neutral mass spectrometry, which destructively probes the whole thickness of the absorber (%2 lm). The two methods show increasingly pronounced gallium and indium gradients with decreasing maximum substrate temperature. The probing of the complementary depth ranges of the absorbers gives a consistent picture of the in-depth gallium distribution, which provides a solid basis for a comprehensive discussion about the effect of a reduced substrate temperature on the formation of gallium gradients in Cu(In,Ga)Se 2 and the device performance of the corresponding reference solar cells.

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“…Anyway, the maximum band gap at the back contact has to be optimized in order to obtain an improved short-circuit current density. Without back grading the internal quantum efficiency is lowered owing to the lack of quasi-electrical field which helps the photo-generated carriers to reach the contacts [12]. The optimization of band gap grading in CIGS shows an absolute gain in efficiency up to 3% [13].…”

Section: Conduction Band Gradingmentioning

confidence: 99%

A New Approach to Valence and Conduction Band Grading in CIGS Thin Film Solar Cells

Gorji¹,

Perez²,

Reggiani³

et al. 2012

IJET

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Analysis of internal quantum efficiency in double-graded bandgap solar cells including sub-bandgap absorption

Cited by 64 publications

References 17 publications

Microscale solar cells for high concentration on polycrystalline Cu(In,Ga)Se2 thin films

Microscale solar cells for high concentration on polycrystalline Cu(In,Ga)Se2 thin films

Gallium gradients in chalcopyrite thin films: Depth profile analyses of films grown at different temperatures

A New Approach to Valence and Conduction Band Grading in CIGS Thin Film Solar Cells

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