Two-stage growth of smooth Cu(In,Ga)Se2 films using end-point detection

Schöldström, Jens; Keßler, J.; Edoff, Marika

doi:10.1016/j.tsf.2004.11.076

Cited by 18 publications

(10 citation statements)

References 5 publications

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“…A void or an empty crevice is left behind. An analogous void formation mechanism was assumed by Schöldström et al for the CURO process [28] (Cu-rich first stage followed by a Cu-poor stage) and by Kessler et al [13] for the CUPRO process (similar to the three-stage used for our samples). Our findings provide evidence for the hypothesis of Kessler et al [13] that Cu-Se phases segregate at crevices between GBs, and voids form by out-diffusion of Cu during the final deposition stage.…”

Section: Discussionsupporting

confidence: 67%

Voids and compositional inhomogeneities in Cu(In,Ga)Se₂ thin films: evolution during growth and impact on solar cell performance

Avancini

Keller

Carron

et al. 2018

Science and Technology of Advanced Materials

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Structural defects such as voids and compositional inhomogeneities may affect the performance of Cu(In,Ga)Se2 (CIGS) solar cells. We analyzed the morphology and elemental distributions in co-evaporated CIGS thin films at the different stages of the CIGS growth by energy-dispersive x-ray spectroscopy in a transmission electron microscope. Accumulation of Cu-Se phases was found at crevices and at grain boundaries after the Cu-rich intermediate stage of the CIGS deposition sequence. It was found, that voids are caused by Cu out-diffusion from crevices and GBs during the final deposition stage. The Cu inhomogeneities lead to non-uniform diffusivities of In and Ga, resulting in lateral inhomogeneities of the In and Ga distribution. Two and three-dimensional simulations were used to investigate the impact of the inhomogeneities and voids on the solar cell performance. A significant impact of voids was found, indicating that the unpassivated voids reduce the open-circuit voltage and fill factor due to the introduction of free surfaces with high recombination velocities close to the CIGS/CdS junction. We thus suggest that voids, and possibly inhomogeneities, limit the efficiency of solar cells based on three-stage co-evaporated CIGS thin films. Passivation of the voids’ internal surface may reduce their detrimental effects.

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Section: Discussionsupporting

confidence: 67%

Voids and compositional inhomogeneities in Cu(In,Ga)Se₂ thin films: evolution during growth and impact on solar cell performance

Avancini

Keller

Carron

et al. 2018

Science and Technology of Advanced Materials

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“…Another characteristic of our recipe is the relatively long third stage. This allows for a larger process window in our rate-controlled system, which does not use end-point detection [12]. The substrate was kept at a temperature of 300…”

Section: Cigs Recipe Specificsmentioning

confidence: 99%

Effect of gallium grading in Cu(In,Ga)Se2 solar-cell absorbers produced by multi-stage coevaporation

Schleussner

Zimmermann

Wätjen

et al. 2011

Solar Energy Materials and Solar Cells

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This is an author produced version of a paper published in Solar Energy Materials and Solar Cells. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination. AbstractWe investigate Cu(InGa)Se 2 thin films grown in multi-stage coevaporation processes and solar cells fabricated from such absorbers. Despite some interdiffusion during film growth, Ga/(Ga+In) gradients defined via evaporation-profile variations in the process are to a good part retained in the finished film. This indicates that the bandgap can be engineered in this type of process by varying the evaporation profiles, and consequently also that unintended profile variations should be noted and avoided. With front-side gradients the topmost part of many grains seems to be affected by a higher density of lattice defects due to the strong change of gallium content under copper-poor growth conditions. Electrically, both back-side gradients and moderate front-side gradients are shown to yield an improvement of device efficiency. If a front-side gradient is too wide, though, it causes strong voltage-dependent collection and the fill factor is severely reduced.

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“…Figure 6 presents a schematic of the effects of copper-indium back-end layers during post-selenization. According to the previous researches [32,33], the formation of various intermediates such as indium selenide and copper selenide as fluxing agents induced the internal diffusion of atoms to promote grain growth in the CIGS films during selenization reaction. The interaction phenomenon resulted in the diffusion of indium atoms toward the surface of CIGS films gradually, and gallium atoms accumulated in the bottom region of the CIGS films, as shown in figure 6(a).…”

Section: 2mentioning

confidence: 99%

Incorporation of copper–indium back-end layers in the solution-based Cu(In, Ga)Se₂ films: enhancement of photovoltaic performance of fabricated solar cells

Som

2020

Mater. Res. Express

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The morphology and photovoltaic properties of the solution-based Cu(In, Ga)Se 2 films are effectively improved via the incorporation of copper-indium back-end layers in the precursor films. The effects on the concentrations of bimetal-ions solutions to prepare copper-indium back-end layers are investigated in this study. The incorporation of copper-indium back-end layer in the precursor film enhances the internal diffusion between gallium-ions and indium-ions during selenization reaction. Hence, the porous structure in the back-contact region of prepared CIGS films becomes densified, and the bandgap distribution of films shows a gradient profile. The densified morphology and gradient bandgap reduce the carrier recombination and improve the carrier collection of solar cells. In contrast to the pristine precursor film, the precursor film with a copper-indium back-end layer increase the conversion efficiency of prepared solar cells from 8.34% to 11.13%. The enhancement of conversion efficiency is attributed to the improvement of short-circuit current density and fill factor from 25.70 mA cm −2 to 31.79 mA cm −2 and 57.65% to 65.70%, respectively. This study reveals that the photovoltaic properties of solution-based CIGS solar cells can be improved significantly via the incorporation of copper-indium back-end layers into the precursor films. OPEN ACCESS RECEIVED

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Two-stage growth of smooth Cu(In,Ga)Se2 films using end-point detection

Cited by 18 publications

References 5 publications

Voids and compositional inhomogeneities in Cu(In,Ga)Se₂ thin films: evolution during growth and impact on solar cell performance

Voids and compositional inhomogeneities in Cu(In,Ga)Se₂ thin films: evolution during growth and impact on solar cell performance

Effect of gallium grading in Cu(In,Ga)Se2 solar-cell absorbers produced by multi-stage coevaporation

Incorporation of copper–indium back-end layers in the solution-based Cu(In, Ga)Se₂ films: enhancement of photovoltaic performance of fabricated solar cells

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Two-stage growth of smooth Cu(In,Ga)Se2 films using end-point detection

Cited by 18 publications

References 5 publications

Voids and compositional inhomogeneities in Cu(In,Ga)Se2 thin films: evolution during growth and impact on solar cell performance

Voids and compositional inhomogeneities in Cu(In,Ga)Se2 thin films: evolution during growth and impact on solar cell performance

Effect of gallium grading in Cu(In,Ga)Se2 solar-cell absorbers produced by multi-stage coevaporation

Incorporation of copper–indium back-end layers in the solution-based Cu(In, Ga)Se2 films: enhancement of photovoltaic performance of fabricated solar cells

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Voids and compositional inhomogeneities in Cu(In,Ga)Se₂ thin films: evolution during growth and impact on solar cell performance

Voids and compositional inhomogeneities in Cu(In,Ga)Se₂ thin films: evolution during growth and impact on solar cell performance

Incorporation of copper–indium back-end layers in the solution-based Cu(In, Ga)Se₂ films: enhancement of photovoltaic performance of fabricated solar cells