Impact of air‐light exposure on the electrical properties of Cu(In,Ga)Se<sub>2</sub> solar cells

Hölscher, Torsten; Schneider, Thomas; Maiberg, Matthias; Scheer, Roland

doi:10.1002/pip.3041

Cited by 11 publications

(13 citation statements)

References 31 publications

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“…Next, we discuss the changes of the distribution of alkali metals in the CsF‐treated CIGS thin film due to HLS treatment, which is in line with the results presented in previous studies . Figure a shows a SIMS depth profile of CsF‐treated CIGS solar cell before and after HLS treatment.…”

supporting

confidence: 83%

“…Next, we discuss the changes of the distribution of alkali metals in the CsF-treated CIGS thin film due to HLS treatment, which is in line with the results presented in previous studies. [34,[46][47][48] Figure 5a shows a SIMS depth profile of CsF-treated CIGS solar cell before and after HLS treatment. As can be shown, the intensity of K increases at the surface and toward the Mo side after HLS treatment, whereas the Cs signal reduces slightly at the surface with a small increment in the Na signal.…”

Section: Ishwor Khatri* Takahiko Yashiro Tzu-ying Lin Mutsumi Sugimentioning

confidence: 99%

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Metastable Behavior on Cesium Fluoride‐Treated Cu(In_1–x,Ga_x)Se₂ Solar Cells

Khatri

Yashiro

Lin

et al. 2020

Physica Rapid Research Ltrs

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Metastable behavior of cesium fluoride (CsF)‐treated Cu(In1–x,Gax)Se2 (CIGS) solar cells is investigated under heat‐light soaking (HLS) and heat‐soaking (HS) treatments. HLS increases open‐circuit voltage, fill factor, efficiency, and net carrier concentration and decreases short‐circuit current density, whereas heat‐soaking treatment acts oppositely. The performance of a CsF postdeposition treatment to CIGS thin film in selenium vapor, and closer to stoichiometry copper content, did not mitigate the open‐circuit voltage improvement after HLS. These results argue the traditional concept of the VSe–VCu divacancy complex for the total beneficial effect of HLS in alkali‐treated CIGS solar cells. The metastable behavior observed in the CsF‐treated devices due to the HLS and HS treatments is explained by the specific behavior of alkali‐containing new compounds at the surface and/or the migration of alkali metals at the surface and bulk regions.

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supporting

confidence: 83%

Section: Ishwor Khatri* Takahiko Yashiro Tzu-ying Lin Mutsumi Sugimentioning

confidence: 99%

Metastable Behavior on Cesium Fluoride‐Treated Cu(In_1–x,Ga_x)Se₂ Solar Cells

Khatri

Yashiro

Lin

et al. 2020

Physica Rapid Research Ltrs

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“…It is well known that during CIGS solar cell manufacturing, exposure of the absorber surface to ambient air 15 , alkali metal fluorides 16,17 or chemical etchants 18,19 before buffer deposition influences heavily the device's optoelectronic properties. It is likely, but has never been investigated, that CIGS grown under different conditions displays different resilience to point defect formation during and after growth.…”

mentioning

confidence: 99%

Chemical instability at chalcogenide surfaces impacts chalcopyrite devices well beyond the surface

et al. 2020

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The electrical and optoelectronic properties of materials are determined by the chemical potentials of their constituents. The relative density of point defects is thus controlled, allowing to craft microstructure, trap densities and doping levels. Here, we show that the chemical potentials of chalcogenide materials near the edge of their existence region are not only determined during growth but also at room temperature by post-processing. In particular, we study the generation of anion vacancies, which are critical defects in chalcogenide semiconductors and topological insulators. The example of CuInSe 2 photovoltaic semiconductor reveals that single phase material crosses the phase boundary and forms surface secondary phases upon oxidation, thereby creating anion vacancies. The arising metastable point defect population explains a common root cause of performance losses. This study shows how selective defect annihilation is attained with tailored chemical treatments that mitigate anion vacancy formation and improve the performance of CuInSe 2 solar cells.

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“…However, cells with too little Sodium also exhibit poor performance possibly also due to high interface recombination. It has been surmised that Sodium has an ambiguous role for interface recombination and can also lead to passivation of the front surface 47 and back contact 48 . In effect, there is an optimum NaF‐PDT thickness.…”

Section: Discussionmentioning

confidence: 99%

Effect of Na‐PDT and KF‐PDT on the photovoltaic performance of wide bandgap Cu (In,Ga)Se2 solar cells

Zahedi‐Azad

Maiberg

Scheer

2020

Progress in Photovoltaics

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Cu (In,Ga)Se 2 solar cells exhibit higher efficiencies if an appropriate Ga gradient is introduced and if the absorber is doped with sodium (Na) plus a heavier alkali atom such as potassium. However, a Gallium gradient in the presence of Na is challenging because sodium impedes the interdiffusion of elements and influences the gradient. In this contribution, we show that the presence of sodium during growth with the combination of high Ga concentration creates a pronounced gradient that is detrimental for carrier collection. One solution is to avoid Na abundance during absorber growth but to add it to the grown absorber layer via a postdeposition treatment. We investigate the effect of different Na incorporation methods simultaneously with KF-PDT on wide band gap CIGSe absorbers. By preparation on alkali-free substrates and application of alkalis (NaF and KF) onto a grown CIGSe layer, we show by smoothening of the Gallium gradient a large improvement in the solar cell performance from 4% to 8%. Another way to optimize the gradient in the presence of Na is the modification of the three-stage method. This yields the best efficiency of 10% in our laboratory at an integral GGI of 0.8. By means of temperature-dependent JV measurements, we show that the additional postdeposition of KF induces a barrier for the diode current. We conclude that KF-PDT induces a new thin layer at the CIGSe surface that has a lower valence band edge relative to the CIGSe bulk and is responsible for the double-diode behavior. This barrier can also explain the V oc (T) saturation at low temperature.

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Impact of air‐light exposure on the electrical properties of Cu(In,Ga)Se₂ solar cells

Cited by 11 publications

References 31 publications

Metastable Behavior on Cesium Fluoride‐Treated Cu(In_1–x,Ga_x)Se₂ Solar Cells

Metastable Behavior on Cesium Fluoride‐Treated Cu(In_1–x,Ga_x)Se₂ Solar Cells

Chemical instability at chalcogenide surfaces impacts chalcopyrite devices well beyond the surface

Effect of Na‐PDT and KF‐PDT on the photovoltaic performance of wide bandgap Cu (In,Ga)Se2 solar cells

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Impact of air‐light exposure on the electrical properties of Cu(In,Ga)Se2 solar cells

Cited by 11 publications

References 31 publications

Metastable Behavior on Cesium Fluoride‐Treated Cu(In1–x,Gax)Se2 Solar Cells

Metastable Behavior on Cesium Fluoride‐Treated Cu(In1–x,Gax)Se2 Solar Cells

Chemical instability at chalcogenide surfaces impacts chalcopyrite devices well beyond the surface

Effect of Na‐PDT and KF‐PDT on the photovoltaic performance of wide bandgap Cu (In,Ga)Se2 solar cells

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Impact of air‐light exposure on the electrical properties of Cu(In,Ga)Se₂ solar cells

Metastable Behavior on Cesium Fluoride‐Treated Cu(In_1–x,Ga_x)Se₂ Solar Cells

Metastable Behavior on Cesium Fluoride‐Treated Cu(In_1–x,Ga_x)Se₂ Solar Cells