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Effect of the cadmium chloride treatment on RF sputtered Cd0.6Zn0.4Te films for application in multijunction solar cells

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journal contribution
posted on 2016-09-06, 12:57 authored by Tushar M. Shimpi, Jason M. Kephart, Drew E. Swanson, Amit Munshi, Walajabad S. Sampath, Ali AbbasAli Abbas, Michael WallsMichael Walls
Single phase Cd0.6 Zn 0.4Te (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 (CdCl2) at different temperatures using a constant treatment time. The effect of the CdCl2 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 CdCl2 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 CdCl2 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 CdCl2. 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 CdCl2 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.

Funding

This work was supported by National Science Foundation-Industrial/University Center of Research and Cooperation for Next Generation Photovoltaics group and the authors would like to express gratitude.

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Published in

Vacuum Science & Technology A

Volume

34

Issue

5

Citation

SHIMPI, T.M. ... et al, 2016. Effect of the cadmium chloride treatment on RF sputtered Cd0.6Zn0.4Te films for application in multijunction solar cells. Journal of Vacuum Science & Technology A, 34 (5), 051202.

Publisher

AIP Publishing / © American Vacuum Society

Version

  • AM (Accepted Manuscript)

Acceptance date

2016-08-01

Publication date

2016-08-12

Notes

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in SHIMPI, T.M. ... et al, 2016. Effect of the cadmium chloride treatment on RF sputtered Cd0.6Zn0.4Te films for application in multijunction solar cells. Journal of Vacuum Science & Technology A, 34 (5), 051202 and may be found at http://dx.doi.org/10.1116/1.4960979

ISSN

0734-2101

Language

  • en

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