Growth of Co-evaporated Cu(In,Ga)Se<sub>2</sub> – The Influence of Rate Profiles on Film Morphology

Bodegård, Marika; Keßler, J.; Lundberg, Olle; Schöldström, Jens; Stolt, Lars

doi:10.1557/proc-668-h2.2

Cited by 7 publications

(5 citation statements)

References 3 publications

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“…One feature of the three‐stage process is the spontaneously obtained notch‐type grading profile of Ga. It has been shown that such profiles with a higher Ga content toward the back contact and the front surface can improve the final performance of the solar cell . The grading is known to form because of the slower reaction of Ga, compared with In, with the incoming Cu during the film growth .…”

Section: Resultsmentioning

confidence: 99%

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Influence of high growth rates on evaporated Cu(In,Ga)Se₂ layers and solar cells

Chirilă

Seyrling

Buecheler

et al. 2011

Progress in Photovoltaics

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Thin film solar cells based on polycrystalline Cu(In,Ga)Se2 were prepared by elemental co‐evaporation using modified three‐stage processes on soda lime glass substrates at a low substrate temperature of 450°C intended for application on polyimide foils. The growth rates in the different stages of the growth process were varied, and it was observed that the final composition profile and structural quality of the film are mainly determined by the growth rate in the third stage. Application of high growth rates in the second stage was found to have no significant impact on layer morphology and gallium grading profile, which was confirmed by scanning electron microscopy, secondary ion mass spectroscopy, and x‐ray diffraction measurements. On the other hand, scanning electron microscopy cross sections revealed that high growth rates in the third stage lead to a fine‐grained structure toward the surface as well as smaller grains toward the back contact. Secondary ion mass spectroscopy and x‐ray diffraction measurements of such layers revealed a pronounced gallium grading profile, while Raman spectroscopy showed strong occurrence of group III‐rich phases in the near‐surface region. The final device performance was found to deteriorate by about 10% relative to the baseline process efficiency when growth rates of up to 500 nm min−1 were applied in the second stage or 600 nm min−1 in the third stage. Copyright © 2011 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 99%

“…performance of the solar cell [15,16,[28][29][30][31][32][33][34][35][36][37][38]. The grading is known to form because of the slower reaction of Ga, compared with In, with the incoming Cu during the film growth [39].…”

Section: Composition Analysismentioning

confidence: 99%

Influence of high growth rates on evaporated Cu(In,Ga)Se₂ layers and solar cells

Chirilă

Seyrling

Buecheler

et al. 2011

Progress in Photovoltaics

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“…The first chamber uses a scheme with endpoint detection for Cu/Ga control [14]. The second chamber uses a mass spectrometer to control the rates of the evaporation sources which follow pre programmed cosine 3 (x) profiles [14]. The CGS films are called CGS1 if they are deposited in the first chamber and CGS2 if they are deposited in the second chamber.…”

Section: Methodsmentioning

confidence: 99%

CuGaSe2 solar cells using atomic layer deposited Zn(O,S) and (Zn,Mg)O buffer layers

et al. 2009

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“…Only limited information is available in the literature addressing the tolerance of the laboratory processes to several variations. Some studies have been published related to CIGS thickness, 6 maximum deposition temperature and time spent by the film in the Cu-rich stage, 7,8 Na content, 9,10 rate profiles, 11 and final overall Cu/(In+Ga) atomic ratio. 12 Not only are there additional, at times more important, absorber characteristics that define the quality of the resulting absorber for use in a PV device, but these experiments were conducted without correlation to practical commercial fabrication methods.…”

Section: A Backgroundmentioning

confidence: 99%

Tolerance of Three-Stage CIGS Deposition to Variations Imposed by Roll-to-Roll Processing: Phase II Annual Report, May 2003--May 2004

Beck¹,

Repins²

2004

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Co-evaporation of CuIn x Ga 1-x Se 2 (CIGS) via two-stage and three-stage processes has been used in a variety of laboratories throughout the world to produce small-area devices with efficiencies greater than 15%. Thus, these deposition methods have come to be viewed as laboratory standards for the formation of CIGS absorbers used in respective photovoltaic devices. Although quite successful and relative easy to implement on a small R&D scale, scale-up to a commercially viable level proves to be rather challenging, as a number of conditions are encountered during continuous manufacturing that differ from the laboratory process. Such differences include both those imposed by continuous processing of moving substrates, and those implemented to decrease costs and increase throughput. It is therefore beneficial to understand the tolerance of the established laboratory processes to variations in deposition procedures. Research under this program consists of four basic parts to examine the tolerance of the established laboratory process to variations in deposition procedures: 1. Setting up the National Renewable Energy Laboratory (NREL)-developed three-stage CIGS laboratory process in a bell jar. (Phase I) 2. Characterizing the GSE roll-to-roll production chambers and device finishing steps in terms of the variables important to the laboratory processes. (Phase II) 3. Using the bell jar system to step incrementally from the NREL process to the conditions experienced by a sample during manufacturing, and characterizing the resulting films and devices. (Phase II and III) 4. Applying the process sensitivity information gained from the bell jar system to the production systems to realize improved device performance, yield, and process robustness. (Phase II and III) Work during Phase II progressed in three major areas: production system characterization, quantification of process sensitivities in the bell jar, and application of results to the production roll-coaters. To form a complete picture of conditions in the production systems, metals flux profiles as a function of Se pressure were documented, Se impingement rates were derived from sensor data, and thermocouple data was used to estimated temperature profiles. In the bell jar, the impact of the following process variations on device performance were quantified: CIGS cool-down rate, cool-down Se flux, venting temperature, shortened time between venting and CdS, maximum Cu ratio, and final Cu ratio. Related to production systems, the following topics were investigated: process robustness and device performance as a function of maximum and final Cu ratio, real-time sensing of maximum Cu ratio, effect of processing delays between CIGS and CdS, transparent conducting oxide stability with exposure to damp heat, and improved junction formation via thioacetamide treatment. Phase III tasks will build on this year's results: In the bell jar, several process sensitivity investigations will be concluded, and some new ones begun. These investigations will include use of less expen...

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Growth of Co-evaporated Cu(In,Ga)Se₂ – The Influence of Rate Profiles on Film Morphology

Cited by 7 publications

References 3 publications

Influence of high growth rates on evaporated Cu(In,Ga)Se₂ layers and solar cells

Influence of high growth rates on evaporated Cu(In,Ga)Se₂ layers and solar cells

CuGaSe2 solar cells using atomic layer deposited Zn(O,S) and (Zn,Mg)O buffer layers

Tolerance of Three-Stage CIGS Deposition to Variations Imposed by Roll-to-Roll Processing: Phase II Annual Report, May 2003--May 2004

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Growth of Co-evaporated Cu(In,Ga)Se2 – The Influence of Rate Profiles on Film Morphology

Cited by 7 publications

References 3 publications

Influence of high growth rates on evaporated Cu(In,Ga)Se2 layers and solar cells

Influence of high growth rates on evaporated Cu(In,Ga)Se2 layers and solar cells

CuGaSe2 solar cells using atomic layer deposited Zn(O,S) and (Zn,Mg)O buffer layers

Tolerance of Three-Stage CIGS Deposition to Variations Imposed by Roll-to-Roll Processing: Phase II Annual Report, May 2003--May 2004

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Product

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Growth of Co-evaporated Cu(In,Ga)Se₂ – The Influence of Rate Profiles on Film Morphology

Influence of high growth rates on evaporated Cu(In,Ga)Se₂ layers and solar cells

Influence of high growth rates on evaporated Cu(In,Ga)Se₂ layers and solar cells