Analysis of Bulk and Interface Phenomena in CdTe/CdS Thin-Film Solar Cells

Terheggen, M.; Heinrich, Helge; Kostorz, G.; Baetzner, D. L.; Romeo, Alessandro; Tiwari, Ayodhya N.

doi:10.1023/b:ints.0000028655.11608.c7

Cited by 50 publications

(40 citation statements)

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“…However, the relative change in the diffusion profile and diffusion depth between the three samples is less than that observed in the window layer and considerably less than that observed in previous studies. 16,17 This is consistent with the minimal structural changes observed in the CdTe following activation. This also further emphasises the important role that even a gentle (low temperature) Cl-activation can have on the Cd 1Àx Zn x S alloy window layers investigated here.…”

Section: B Structural Changes In Devicessupporting

confidence: 87%

“…On the other hand, annealing appears to have led to some homogenisation of the Cd 1Àx Zn x S layer. The ability of CdCl 2 activation to enhance inter-diffusion has previously been reported 16,17 but in the case of S (from the CdS window layer) into CdTe, it is interesting to observe here the inter-diffusion effects in Cd 1Àx Zn x S alloy window layers.…”

Section: B Structural Changes In Devicesmentioning

confidence: 67%

“…Both effects were observed to be greater after CdCl 2 activation. Others have also made this observation for CdS/CdTe cells, 15,16 though in those examples major restructuring was observed in both the CdS and CdTe layers.…”

Section: B Structural Changes In Devicesmentioning

confidence: 75%

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CdCl2 treatment related diffusion phenomena in Cd1−xZnxS/CdTe solar cells

Kartopu

Taylor

Clayton

et al. 2014

Journal of Applied Physics

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Utilisation of wide bandgap Cd1−xZnxS alloys as an alternative to the CdS window layer is an attractive route to enhance the performance of CdTe thin film solar cells. For successful implementation, however, it is vital to control the composition and properties of Cd1−xZnxS through device fabrication processes involving the relatively high-temperature CdTe deposition and CdCl2 activation steps. In this study, cross-sectional scanning transmission electron microscopy and depth profiling methods were employed to investigate chemical and structural changes in CdTe/Cd1−xZnxS/CdS superstrate device structures deposited on an ITO/boro-aluminosilicate substrate. Comparison of three devices in different states of completion—fully processed (CdCl2 activated), annealed only (without CdCl2 activation), and a control (without CdCl2 activation or anneal)—revealed cation diffusion phenomena within the window layer, their effects closely coupled to the CdCl2 treatment. As a result, the initial Cd1−xZnxS/CdS bilayer structure was observed to unify into a single Cd1−xZnxS layer with an increased Cd/Zn atomic ratio; these changes defining the properties and performance of the Cd1−xZnxS/CdTe device.

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Section: B Structural Changes In Devicessupporting

confidence: 87%

Section: B Structural Changes In Devicesmentioning

confidence: 67%

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CdCl2 treatment related diffusion phenomena in Cd1−xZnxS/CdTe solar cells

Kartopu

Taylor

Clayton

et al. 2014

Journal of Applied Physics

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“…While the CdS/CdTe interface suffers from a 10% lattice mismatch that produces misfit dislocations, 57 CdTe absorber layers can be separated in two groups, depending on the substrate temperature used during the CdTe growth. For low-temperature processes (e.g., HVE) CdTe grows epitaxially on the CdS grains, with the {111} planes of CdTe being parallel to the {0001} planes of CdS.…”

Section: Cdtementioning

confidence: 99%

Development of thin‐film Cu(In,Ga)Se₂ and CdTe solar cells

Romeo¹,

Terheggen²,

Abou‐Ras³

et al. 2004

Progress in Photovoltaics

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354

192

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Cu(In,Ga)Se2 and CdTe heterojunction solar cells grown on rigid (glass) or flexible foil substrates require p‐type absorber layers of optimum optoelectronic properties and n‐type wide‐bandgap partner layers to form the p–n junction. Transparent conducting oxide and specific metal layers are used for front and back electrical contacts. Efficiencies of solar cells depend on various deposition methods as they control the optoelectronic properties of the layers and interfaces. Certain treatments, such as addition of Na in Cu(In,Ga)Se2 and CdCl2 treatment of CdTe have a direct influence on the electronic properties of the absorber layers and efficiency of solar cells. Processes for the development of superstrate and substrate solar cells are reviewed. Copyright © 2004 John Wiley & Sons, Ltd.

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“…By varying the glancing angle of the FIB, it is also possible to profile the microstructure as a function of film thickness. FIB has also been used to examine grain boundary electrical behavior at specific sites using Electron Beam Induced Current (EBIC) measurements [2].In addition to grain boundary structure, EBSD provides information on orientation, grain size and shape, and phase distributions. Figure 2 shows a Local Orientation Spread Map with a bimodal grain size structure of small strained grains and larger strain free twinned grains from a partially recrystallized CdTe film.…”

mentioning

confidence: 99%

Microstructural Analysis of CdTe Thin Films using EBSD and FIB

Nowell¹,

Wright²,

Carpenter³

2009

Microsc Microanal

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The driving force to develop technologies and materials for alternative energy production has been increasing due to economic and political factors. The development and application of photovoltaic (PV) solar cell materials for converting light into electricity is well documented, and has demonstrated a significant growth rate that is expected to continue. Due to the cost of silicon wafers used in traditional solar cells, thin film based alternatives using less material and alternative substrates have been developed. Cadmium telluride (CdTe) is one such alternative, and has been used to produce commercial solar cells. However research is currently continuing to improve the efficiency of these devices.One area of research is determining the role of grain boundaries in device performance. Typically grain boundaries are considered defects within a material. However polycrystalline CdTe cells have exhibited higher efficiencies than single crystal cells and the reason for this is not well understood. Grain boundaries can act as diffusion pathways for different elements, and elemental segregation can occur. This can result in a change in electrical properties of the boundaries.Electron backscatter diffraction (EBSD) and Orientation Imaging Microscopy (OIM) is a well suited analytical microanalysis technique for investigating this type of thin film material. By providing spatially specific orientation data on a sub-micron scale, it is possible to measure the grain boundary structure with enough data for statistical significance. This allows for the identification and differentiation of different grain boundary types such as twin boundaries, low angle boundaries, and random high angle boundaries. These different boundary types may have significantly different electrical properties and their distributions could be varied through grain boundary engineering principles.Often CdTe films have a surface roughness that limits EBSD collection efficiency. Previous work has shown that this efficiency can be improved through mechanical and broad beam ion polishing [1]. An alternative approach is to use a Focused Ion Beam (FIB) for site specific preparation. Figure 1 shows EBSD Image Quality (IQ) maps from ion broad beam and FIB prepared surfaces, where better grain contrast is obtained using the FIB. By varying the glancing angle of the FIB, it is also possible to profile the microstructure as a function of film thickness. FIB has also been used to examine grain boundary electrical behavior at specific sites using Electron Beam Induced Current (EBIC) measurements [2].In addition to grain boundary structure, EBSD provides information on orientation, grain size and shape, and phase distributions. Figure 2 shows a Local Orientation Spread Map with a bimodal grain size structure of small strained grains and larger strain free twinned grains from a partially recrystallized CdTe film. This data can help understand the evolution that occurs during thermal processing.

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Analysis of Bulk and Interface Phenomena in CdTe/CdS Thin-Film Solar Cells

Cited by 50 publications

References 3 publications

CdCl2 treatment related diffusion phenomena in Cd1−xZnxS/CdTe solar cells

CdCl2 treatment related diffusion phenomena in Cd1−xZnxS/CdTe solar cells

Development of thin‐film Cu(In,Ga)Se₂ and CdTe solar cells

Microstructural Analysis of CdTe Thin Films using EBSD and FIB

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Analysis of Bulk and Interface Phenomena in CdTe/CdS Thin-Film Solar Cells

Cited by 50 publications

References 3 publications

CdCl2 treatment related diffusion phenomena in Cd1−xZnxS/CdTe solar cells

CdCl2 treatment related diffusion phenomena in Cd1−xZnxS/CdTe solar cells

Development of thin‐film Cu(In,Ga)Se2 and CdTe solar cells

Microstructural Analysis of CdTe Thin Films using EBSD and FIB

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Product

Resources

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Development of thin‐film Cu(In,Ga)Se₂ and CdTe solar cells