Enhancements in specimen preparation of Cu(In,Ga)(S,Se)2 thin films

Abou‐Ras, Daniel; Marsen, B.; Rissom, T.; Frost, Frank; Schulz, H.; Bauer, Frank; Efimova, Varvara; Hoffmann, Volker; Eicke, A.

doi:10.1016/j.micron.2011.11.004

Cited by 18 publications

(17 citation statements)

References 12 publications

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“…TEM lamellae have been prepared using a FEI Strata DB235 equipped with a Ga‐based focused ion beam, using the in situ lift‐out method . To limit the formation of Cu‐rich precipitates on the surface of the lamellae by the ion milling, XeF2 was used during the final 5‐kV polishing step . The relative thickness of the lamella was maintained between t/λ = 0.15–0.5.…”

Section: Experimental Methodsmentioning

confidence: 99%

Deep surface Cu depletion induced by K in high‐efficiency Cu(In,Ga)Se₂ solar cell absorbers

Donzel‐Gargand

Thersleff²,

Keller

et al. 2018

Progress in Photovoltaics

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Abstract:In this work we used K-rich glass substrates to provide potassium during the co-evaporation of CIGS absorber layers. Subsequently, we applied a post-deposition treatment (PDT) using KF or RbF to some of the grown absorbers. It was found that the presence of K during the growth of the CIGS layer led to cell efficiencies beyond 17%, and the addition of a PDT pushed it beyond 18 %. The major finding of this work is the observation of discontinuous 100-200 nm-deep Cudepleted patches in the vicinity of the CdS buffer layer, correlated with the presence of K during the growth of the absorber layer. The PDT had no influence on the formation of these patches. A second finding concerns the composition of the Cu-depleted areas, where an anti-correlation between Cu and both In and K was measured using scanning transmission electron microscopy (STEM). Furthermore, a steeper Ga/(In+Ga) ratio gradient was measured for the absorbers grown with the presence of K, suggesting that K hinders the group III element inter-diffusion. Finally, no Cd in-diffusion to the CIGS layer could be detected. This indicates that if Cd Cu substitution occurs, either their concentration is below our instrumental detection limit, or its presence is contained within the first 6 nm from the CdS/CIGS interface.

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Section: Experimental Methodsmentioning

confidence: 99%

Deep surface Cu depletion induced by K in high‐efficiency Cu(In,Ga)Se₂ solar cell absorbers

Donzel‐Gargand

Thersleff²,

Keller

et al. 2018

Progress in Photovoltaics

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“…15 Thus, we used XeF 2 as reactive gas during the last step of milling to avoid the creation of such agglomerates. 16 No agglomerates have been observed on the final lamellas, as it can be clearly seen in the scanning electron microscopy (SEM) image in Figure 1.…”

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confidence: 90%

Improved Ga grading of sequentially produced Cu(In,Ga)Se2 solar cells studied by high resolution X-ray fluorescence

Schöppe

Schnohr

Oertel

et al. 2015

Applied Physics Letters

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There is particular interest to investigate compositional inhomogeneity of Cu(In,Ga)Se2 solar cell absorbers. We introduce an approach in which focused ion beam prepared thin lamellas of complete solar cell devices are scanned with a highly focused synchrotron X-ray beam. Analyzing the resulting fluorescence radiation ensures high resolution compositional analysis combined with high spatial resolution. Thus, we are able to detect subtle variations of the Ga/(Ga + In) ratio down to 0.01 on a submicrometer scale. We observed that for sequentially processed solar cells a higher selenization temperature leads to absorbers with almost homogenous Ga/(Ga + In) ratio, which significantly improved the conversion efficiency.

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“…During acquisition of depth profiles, all investigated samples, including the crystals for calibration, were cooled with liquid nitrogen to minimize migration and clustering of surface atoms. Sputtering of CIGS layers without cooling causes a roughening of the sputtered surface and results in a decreased depth resolution and distortion of the depth profiles …”

Section: Methodsmentioning

confidence: 99%

“…Sputtering of CIGS layers without cooling causes a roughening of the sputtered surface and results in a decreased depth resolution and distortion of the depth profiles. [22,23] Results and discussion [8] Nakada reported that CBD Zn(O,S) grown on CIGS exhibits small polycrystalline grains containing a large number of defects. [24] In contrast, sputtered Zn(O,S) layers yielding best efficiencies show a high degree of crystallinity, as found by several groups.…”

Section: Methodsmentioning

confidence: 99%

Depth profiling with SNMS and SIMS of Zn(O,S) buffer layers for Cu(In,Ga)Se₂ thin‐film solar cells

Eicke

Ciba

Hariskos

et al. 2013

Surface & Interface Analysis

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Zn(O,S) is a promising candidate to replace the commonly used CdS buffer layer for Cu(In,Ga)Se2 (CIGS) thin‐film solar cells due to its non‐toxicity and its potential to enhance the conversion efficiency of the CIGS solar cell. The composition of chemical bath deposited (CBD) and sputtered Zn(O,S) layers with thicknesses well below 100 nm was determined by sputtered neutral and secondary ion mass spectrometry (SNMS and SIMS). Despite numerous mass interferences of double‐charged atoms and dimers with single Zn, O and S isotopes, we developed an evaluation algorithm for quantification of SNMS depth profiles of Zn(O,S) layers. In particular, the superposition of double‐charged S and Zn atoms with O and S isotopes is accounted for numerically in the quantification procedure. For sputtered Zn(O,S) layers, the S/(S + O) atomic ratio and the vertical composition profile can be controlled by the O2 content in the gas flow and the substrate temperature during sputtering whereas for CBD Zn(O,S) the S/(S + O) ratio is constant around 0.7–0.8. A Cu‐depleted layer of about 5 nm on the CIGS surface after buffer deposition was observed for both preparation methods. With negative SIMS, we found more hydroxides and carbon residues in CBD Zn(O,S) as compared to sputtered layers. Best cell performance with sputtered Zn(O,S) layers was achieved for S/(S + O) ratios of 0.25–0.40, yielding efficiencies up to 13%. Our solar cells with CBD Zn(O,S) buffers exhibit higher efficiencies due to an improved open‐circuit voltage. Copyright © 2013 John Wiley & Sons, Ltd.

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Enhancements in specimen preparation of Cu(In,Ga)(S,Se)2 thin films

Cited by 18 publications

References 12 publications

Deep surface Cu depletion induced by K in high‐efficiency Cu(In,Ga)Se₂ solar cell absorbers

Deep surface Cu depletion induced by K in high‐efficiency Cu(In,Ga)Se₂ solar cell absorbers

Improved Ga grading of sequentially produced Cu(In,Ga)Se2 solar cells studied by high resolution X-ray fluorescence

Depth profiling with SNMS and SIMS of Zn(O,S) buffer layers for Cu(In,Ga)Se₂ thin‐film solar cells

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Enhancements in specimen preparation of Cu(In,Ga)(S,Se)2 thin films

Cited by 18 publications

References 12 publications

Deep surface Cu depletion induced by K in high‐efficiency Cu(In,Ga)Se2 solar cell absorbers

Deep surface Cu depletion induced by K in high‐efficiency Cu(In,Ga)Se2 solar cell absorbers

Improved Ga grading of sequentially produced Cu(In,Ga)Se2 solar cells studied by high resolution X-ray fluorescence

Depth profiling with SNMS and SIMS of Zn(O,S) buffer layers for Cu(In,Ga)Se2 thin‐film solar cells

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Product

Resources

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Deep surface Cu depletion induced by K in high‐efficiency Cu(In,Ga)Se₂ solar cell absorbers

Deep surface Cu depletion induced by K in high‐efficiency Cu(In,Ga)Se₂ solar cell absorbers

Depth profiling with SNMS and SIMS of Zn(O,S) buffer layers for Cu(In,Ga)Se₂ thin‐film solar cells