Effect of the cadmium chloride treatment on RF sputtered Cd{sub 0.6}Zn{sub 0.4}Te films for application in multijunction solar cells

Journal Article · Thu Sep 15 00:00:00 EDT 2016 · Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films

DOI:https://doi.org/10.1116/1.4960979· OSTI ID:22592842

Kephart, Jason M.; Swanson, Drew E.; Munshi, Amit H.; Sampath, Walajabad S. ^[1]; Abbas, A.; Walls, John M. ^[2]

---

1. Department of Mechanical Engineering, Colorado State University, 1320 Campus Delivery, Fort Collins, Colorado 80523 (United States)
2. CREST (Centre for Renewable Energy Systems and Technology), Loughborough University, Loughborough LE11 3TU (United Kingdom)

Single phase Cd{sub 0.6}Zn{sub 0.4}Te (CdZnTe) films of 1 μm thickness were deposited by radio frequency planar magnetron sputter deposition on commercial soda lime glass samples coated with fluorine-doped tin oxide and cadmium sulphide (CdS). The stack was then treated with cadmium chloride (CdCl{sub 2}) at different temperatures using a constant treatment time. The effect of the CdCl{sub 2} treatment was studied using optical, materials, and electrical characterization of the samples and compared with the as-deposited CdZnTe film with the same stack configuration. The band gap deduced from Tauc plots on the as-deposited CdZnTe thin film was 1.72 eV. The deposited film had good crystalline quality with a preferred orientation along the {111} plane. After the CdCl{sub 2} treatment, the absorption edge shifted toward longer wavelength region and new peaks corresponding to cadmium telluride (CdTe) emerged in the x-ray diffraction pattern. This suggested loss of zinc after the CdCl{sub 2} treatment. The cross sectional transmission electron microscope images of the sample treated at 400 °C and the energy dispersive elemental maps revealed the absence of chlorine along the grain boundaries of CdZnTe and residual CdTe. The presence of chlorine in the CdTe devices plays a vital role in drastically improving the device performance which was not observed in CdZnTe samples treated with CdCl{sub 2}. The loss of zinc from the surface and incomplete recrystallization of the grains together with the presence of high densities of stacking faults were observed. The surface images using scanning electron microscopy showed that the morphology of the grains changed from small spherical shape to large grains formed due to the fusion of small grains with distinct grain boundaries visible at the higher CdCl{sub 2} treatment temperatures. The absence of chlorine along the grain boundaries, incomplete recrystallization and distinct grain boundaries is understood to cause the poor performance of the fabricated devices.

• OSTI ID: 22592842
• Journal Information: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films, Vol. 34, Issue 5; Other Information: (c) 2016 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0734-2101
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CADMIUM CHLORIDES
CADMIUM SULFIDES
CADMIUM TELLURIDES
CHLORINE
DEPOSITS
DOPED MATERIALS
FLUORINE
GRAIN BOUNDARIES
GRAIN ORIENTATION
MAGNETRONS
RADIOWAVE RADIATION
SCANNING ELECTRON MICROSCOPY
SOLAR CELLS
SPHERICAL CONFIGURATION
THIN FILMS
TIN OXIDES
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
ZINC
CDZNTE SEMICONDUCTOR DETECTORS