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The roles of ZnTe buffer layers on CdTe solar cell performance

journal contribution
posted on 2016-02-26, 14:02 authored by Colin A. Wolden, Ali AbbasAli Abbas, Jiaojiao Li, David R. Diercks, Daniel M. Meysing, Timothy R. Ohno, Joseph D. Beach, Teresa M. Barnes, Michael WallsMichael Walls
The use of ZnTe buffer layers at the back contact of CdTe solar cells has been credited with contributing to recent improvements in both champion cell efficiency and module stability. To better understand the controlling physical and chemical phenomena, high resolution transmission electron microscopy (HR-TEM) and atom probe tomography (APT) were used to study the evolution of the back contact region during rapid thermal processing (RTP) of this layer. After activation the ZnTe layer, initially nanocrystalline and homogenous, transforms into a bilayer structure consisting of a disordered region in contact with CdTe characterized by significant Cd-Zn interdiffusion, and a nanocrystalline layer that shows evidence of grain growth and twin formation. Copper, co-evaporated uniformly within ZnTe, is found to dramatically segregate and aggregate after RTP, either collecting near the ZnTe|Au interface or forming CuxTe clusters in the CdTe layer at defects or grain boundaries near the interface. Analysis of TEM images revealed that Zn accumulates at the edge of these clusters, and three-dimensional APT images confirmed that these are core-shell nanostructures consisting of Cu1.4Te clusters encased in Zn. These changes in morphology and composition are related to cell performance and stability.

Funding

CAW, JL, DRD, TRO, and JDB gratefully acknowledge the Bay Area Photovoltaic Consortium for their support of this work under Department of Energy Award no. DE-EE0004946. AA and JMW was funded by UKERC through the EPSRC Supergen SuperSolar Hub. DMM and TMB were supported by the U.S. Department of Energy through the SunShot Foundational Program to Advance Cell Efficiency (F-PACE) under Contract no. DE-AC36-08-GO28308.

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Research Unit

  • Centre for Renewable Energy Systems Technology (CREST)

Published in

Solar Energy Materials and Solar Cells

Volume

147

Pages

203 - 210

Citation

WOLDEN, C.A. ... et al, 2016. The roles of ZnTe buffer layers on CdTe solar cell performance. Solar Energy Materials and Solar Cells, 147, pp. 203 - 210.

Publisher

© Elsevier

Version

  • VoR (Version of Record)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Publication date

2016

Notes

This article is closed access.

ISSN

0927-0248

Language

  • en

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