Energy gap variations and structural phase changes in CdSTe alloy thin films

Hill, R.; Richardson, D.J.

doi:10.1016/0040-6090(73)90216-2

Cited by 59 publications

(19 citation statements)

References 7 publications

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“…[3][4][5] This may be explained by the parabolic dependence of the band gap on the composition; many workers [6][7][8][9][10][11] Thin films of CdS x Te 1-x (0 ≤ x ≤ 1) have been prepared by vacuum evaporation from solid solutions. Although the growth of this interfacial layer has been used to explain limited cell efficiency, its effects have not been fully understood.…”

Section: Introductionmentioning

confidence: 99%

Optical properties of CdSxTe1−x polycrystalline thin films

Wood

Lane

Rogers

et al. 1999

Journal of Elec Materi

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Section: Introductionmentioning

confidence: 99%

Optical properties of CdSxTe1−x polycrystalline thin films

Wood

Lane

Rogers

et al. 1999

Journal of Elec Materi

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“…Despite the wide miscibility gap, some groups have been able to fabricate single-phase thin films of CdTel-xSx with x in the middle of the miscibility gap [6][7][8][9]. In order to reconcile the existence of these films with the equilibrium phase diagrams, it must be assumed that these films were either metastable or kinetically limited.…”

Section: Introductionmentioning

confidence: 99%

Thin-Film Cadmium Sulfide/Cadmium Telluride Alloys

1996

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Thin films of CdTel-xSx with bulk atomic compositions, x=-[S]/([S]+[Te]), ranging from 0 to 0.45 were deposited by vacuum co-evaporation of CdTe and CdS with substrate temperatures of 200 and 250'C. X-ray diffraction analysis revealed that films with x < 0.3 were predominately single phase having the zincblende structure. Films with 0.35 < x < 0.45 contained the wurtzite modification. Lattice parameter determination indicated that each phase exists with compositions well within the miscibility gap shown on published equilibrium phase diagrams. The variation of the optical band gap with x was determined by measuring transmission and reflection of the films. Heat treatment at 415'C in the presence of CdC1 2 caused the films to segregate into two phases consistent with the phase diagram. If the CdC1 2 is assumed to only promote the phase segregation process, then the compositions of the two phases after heat treatment may be taken as measurements of the solubility limits of S in CdTe and Te in CdS respectively. The solubility limit of S in CdTe was thus determined to be 5.8% at 415'C which is the temperature used for the common CdC1 2 treatment of CdTe-based solar cells. An analysis of CdTe/CdS solar cell device structures shows that the atomic composition of alloys created by interdiffusion are consistent with these solubility limits.

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“…For mixed crystal films formed at lower temperatures, from 120°C to 200°C, a continuous range of alloys can be obtained [31,33,35,36,37]. For the mixed films, heating above ~300°C induces phase segregation in accordance with the existence of the equilibrium miscibility gap found in mixed CdTe-CdS crystals at higher temperature, indicating that single phase films with composition lying within the miscibility gap are deposited in a metastable state.…”

Section: Solubility Limit Determinationmentioning

confidence: 84%

Optimization of Processing and Modeling Issues for Thin Film Solar Cell Devices Including Concepts for the Development of Polycrystalline Multijunctions Annual Subcontract Report, 24 August 1999 - 23 August 2000

Birkmire¹,

Phillips²,

Shafarman³

et al. 2001

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SUMMARYThe overall mission of the Institute of Energy Conversion (IEC) is the development of thin film photovoltaic cells, modules, and related manufacturing technology and the education of students and professionals in photovoltaic technology. The objectives of this 12 month NREL subcontract are to advance the state of the art and the acceptance of thin film PV solar cells in the areas of improved technology for thin film depositions, device fabrication, and material and device characterization and modeling, relating to solar cells based on CuInSe2 and its alloys, on doped and intrinsic microcrystalline Si films, and on CdTe. CuInSe 2 -BASED SOLAR CELLS In-line Evaporation of Cu(InGa)Se 2In-line evaporation is a potentially effective means to achieve the high rate uniform deposition necessary for commercial-scale manufacture of Cu(InGa)Se 2 modules. In this process, the substrate is linearly translated over thermal sources from which the elemental materials are evaporated.An in-line evaporation system for the deposition of Cu(InGa)Se 2 films has been put into operation at IEC. The system's performance in terms of uniform deposition over large areas at relatively high rates and in terms of device performance and reproducibility has been successfully demonstrated. The compositional uniformity across the 6-inch wide deposition zone is within the uncertainty limits of EDS measurements. A set of depositions with translation speeds ranging from 1 to 2.5 inches/min produced films with thicknesses from 2.1 to 0.9 µm. Devices from these runs had efficiencies from 13.2-14.5 %, for thickness > 1 µm, demonstrating the run-to-run reproducibility of the system. The best cell produced with Cu(InGa)Se 2 from this in-line system had 14.9% efficiency. Effect of Deposition Temperature on Cu(InGa)Se 2 Films and DevicesOne means to reduce manufacturing costs for thin film Cu(InGa)Se 2 is by reducing the substrate temperature at which the Cu(InGa)Se 2 layer is deposited. The effect of substrate temperature on the film grain size, morphology, and compositional uniformity and device performance of Cu(InGa)Se 2 deposited at 480°C was characterized and compared to previous results at 400°C and 550°C. At 480°C, the soda lime glass substrate is below the strain point of the glass, reducing handling problems.Cu(InGa)Se 2 films were deposited by multisource elemental evaporation with different deposition sequences to determine the effect of a Cu-rich growth step, i.e., deposition with the Cu molar flux greater than the sum of the In and Ga fluxes. The grain size was determined from atomic force microscopy images. The films deposited at 480°C have comparable grain size and morphology to those deposited at 550°C. However, V oc , FF, and efficiency of devices with films deposited at 550°C were greater. A Cu-rich growth step during the deposition does not affect the measured grain size or device performance at these temperatures. The films deposited at 400°Ciii have smaller grains and poorer device performance. At this lower temperature the Cu-...

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Energy gap variations and structural phase changes in CdSTe alloy thin films

Cited by 59 publications

References 7 publications

Optical properties of CdSxTe1−x polycrystalline thin films

Optical properties of CdSxTe1−x polycrystalline thin films

Thin-Film Cadmium Sulfide/Cadmium Telluride Alloys

Optimization of Processing and Modeling Issues for Thin Film Solar Cell Devices Including Concepts for the Development of Polycrystalline Multijunctions Annual Subcontract Report, 24 August 1999 - 23 August 2000

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