Junction formation in CuInSe[sub 2]-based thin-film devices

Ramanathan, K.; Wiesner, H.; Asher, S.; Bhattacharya, R. N.; Keane, Jim; Contreras, Miguel Á.; Noufi, R.

doi:10.1063/1.57948

Cited by 8 publications

(6 citation statements)

References 8 publications

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“…30 Furthermore, the downward surface band bending observed for state-of-the-art CIGSSe absorbers, [31][32][33][34] which is believed to be caused by positive surface charges, might induce a Cu "electromigration" away from the buffer/absorber interface. 35,36 However, for the CBD-CdS buffer preparation on CIGSSe absorbers it was repeatedly reported in the past that Cu ions were found in used chemical baths, 37 which were obviously leached out of the absorber's surface as long as the buffer was not completely closed and hence must have taken place in the early stages of the CBD. Altogether we believe that Cu, which is leached out of the absorber's surface ͑chemically driven by the chemical bath solution͒ and subsequently is immediately incorporated into the first monolayer͑s͒ of the forming buffer, explains our findings best.…”

Section: -3mentioning

confidence: 99%

Intermixing at the heterointerface between ZnS∕Zn(S,O) bilayer buffer and CuInS2 thin film solar cell absorber

Bär

Ennaoui

Klaer

et al. 2006

Journal of Applied Physics

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The application of Zn compounds as buffer layers was recently extended to wide-gap CuInS 2 ͑CIS͒ based thin-film solar cells. Using an alternative chemical deposition route for the buffer preparation aiming at the deposition of a single-layer, nominal ZnS buffer without the need for any toxic reactants such as hydrazine has helped us to achieve a similar efficiency as respective CdS-buffered reference devices. After identifying the deposited Zn compound, as ZnS / Zn͑S,O͒ bilayer buffer in former investigations ͓M. Bär et al., J. Appl. Phys. 99, 123503 ͑2006͔͒, this time the focus lies on potential diffusion/intermixing processes at the buffer/absorber interface possibly, clarifying the effect of the heat treatment, which drastically enhances the device performance of respective final solar cells. The interface formation was investigated by x-ray photoelectron and x-ray excited Auger electron spectroscopy. In addition, photoelectron spectroscopy ͑PES͒ measurements were also conducted using tunable monochromatized synchrotron radiation in order to gain depth-resolved information. The buffer side of the buffer/absorber heterointerface was investigated by means of the characterization of Zn͑S,O͒ / ZnS / CIS structures where the ZnS / Zn͑S,O͒ bilayer buffer was deposited successively by different deposition times. In order to make the ͑in terms of PES information depth͒ deeply buried absorber side of the buffer/absorber heterointerface accessible for characterization, in these cases the buffer layer was etched away by dilute HCl aq . We found indications that while ͑out-leached͒ Cu from the absorber layer forms together with the educts in the chemical bath a ͓Zn ͑1−Z͒ ,Cu 2Z ͔S-like interlayer between buffer and absorber, Zn is incorporated in the uppermost region of the absorber. Both effects are strongly enhanced by postannealing the Zn͑S,O͒ / ZnS / CIS samples. However, it was determined that the major fraction of the Cu and Zn can be found quite close to the heterointerface in the buffer and absorber layer, respectively. Due to this limited ͑in the range of one monolayer͒ spatial extent, these "diffusion" mechanisms were rather interpreted as a chemical bath deposition induced and heat-treatment promoted Cu-Zn ion exchange at the buffer/absorber interface. Possible impacts of this intermixing on the performance of the final solar cell devices will also be discussed.

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Section: -3mentioning

confidence: 99%

Intermixing at the heterointerface between ZnS∕Zn(S,O) bilayer buffer and CuInS2 thin film solar cell absorber

Bär

Ennaoui

Klaer

et al. 2006

Journal of Applied Physics

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“…Evidence for strong intermixing at the CdS/CIGS interface has been reported [5]. Our previous work [6] generated discussion on some of these issues and work is ongoing. Some diffusion of Cd into the absorber surface region has been observed [7], but this cannot be readily associated with its electrical activity.…”

Section: Methodsmentioning

confidence: 94%

Extrinsic doping effect in the fabrication of CIGS and CIGSS thin film solar cells

Ramanathan

Pankow

Asher

2004

Physica Status Solidi (b)

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PACS 71.55Gs, 72.40.+w, 73.40.Lq, 84.60.Jt This paper describes the effect of Cd and Zn impurities in the formation of photovoltaic junctions using CuInSe 2 -based alloy thin-film absorbers. We compare the properties of solar cells fabricated by using CdS window layers with those obtained by Cd or Zn treatment from the liquid or vapor-phase environments. Efficient solar cells are obtained for the latter two cases, and their properties are comparable to those with CdS window layers. The results are interpreted in terms of the ability of Cd and Zn to produce n-type doping in the surface region of the absorbers.

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“…To further investigate the CBD reaction chemistry, we prepared a series of 50-nmthick CdS films on Mo/glass substrates using our standard CBD process for CIGS substrates, with CdSO 4 as the cadmium source, 40°B70°C deposition temperature, and 100:1 molar ratio of thiourea to Cd (15). The glass substrates were either cerium oxidepolished soda-lime glass or Corning 7059 sodium-free glass.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic analysis of impurity precipitates in CdS films

Webb¹,

Keane²,

Ribelin³

et al. 1999

AIP Conference Proceedings

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Abstract. Impurities in cadmium sulfide (CdS) films are a concern in the fabrication of copper (indium, gallium) diselenide (CIGS) and cadmium telluride (CdTe) photovoltaic devices. Devices incorporating chemical-bath-deposited (CBD) CdS are comparable in quality to devices incorporating purer CdS films grown using vacuum deposition techniques, despite the higher impurity concentrations typically observed in the CBD CdS films. In this paper, we summarize and review the results of Fourier transform infrared (FTIR), Auger, electron microprobe, and Xray photoelectron spectroscopic (XPS) analyses of the impurities in CBD CdS films. We show that these impurities differ as a function of substrate type and film deposition conditions. We also show that some of these impurities exist as 10 2 micron-scale precipitates.

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Junction formation in CuInSe[sub 2]-based thin-film devices

Cited by 8 publications

References 8 publications

Intermixing at the heterointerface between ZnS∕Zn(S,O) bilayer buffer and CuInS2 thin film solar cell absorber

Intermixing at the heterointerface between ZnS∕Zn(S,O) bilayer buffer and CuInS2 thin film solar cell absorber

Extrinsic doping effect in the fabrication of CIGS and CIGSS thin film solar cells

Spectroscopic analysis of impurity precipitates in CdS films

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