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Title: CdCl 2 passivation of polycrystalline CdMgTe and CdZnTe absorbers for tandem photovoltaic cells

Abstract

As single-junction silicon solar cells approach their theoretical limits, tandems provide the primary path to higher efficiencies. CdTe alloys can be tuned with magnesium (CdMgTe) or zinc (CdZnTe) for ideal tandem pairing with silicon. A II-VI/Si tandem holds the greatest promise for inexpensive, high-efficiency top cells that can be quickly deployed in the market using existing polycrystalline CdTe manufacturing lines combined with mature silicon production lines. Currently, all high efficiency polycrystalline CdTe cells require a chloride-based passivation process to passivate grain boundaries and bulk defects. This research examines the rich chemistry and physics that has historically limited performance when extending Cl treatments to polycrystalline 1.7-eV CdMgTe and CdZnTe absorbers. A combination of transmittance, quantum efficiency, photoluminescence, transmission electron microscopy, and energy-dispersive X-ray spectroscopy clearly reveals that during passivation, Mg segregates and out-diffuses, initially at the grain boundaries but eventually throughout the bulk. CdZnTe exhibits similar Zn segregation behavior; however, the onset and progression is localized to the back of the device. After passivation, CdMgTe and CdZnTe can render a layer that is reduced to predominantly CdTe electro-optical behavior. Contact instabilities caused by inter-diffusion between the layers create additional complications. The results outline critical issues and paths for these materials tomore » be successfully implemented in Si-based tandems and other applications.« less

Authors:
 [1]; ORCiD logo [2];  [3]; ORCiD logo [2];  [4]; ORCiD logo [4]; ORCiD logo [3];  [5];  [6];  [2];  [5]
  1. School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287, USA; National Renewable Energy Laboratory, Golden, Colorado 80401, USA
  2. Mechanical Engineering Department, Colorado State University, Fort Collins, Colorado 80523, USA
  3. Loughborough University, Loughborough, United Kingdom
  4. Department of Physics, Arizona State University, Tempe, Arizona 85287, USA
  5. School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287, USA
  6. National Renewable Energy Laboratory, Golden, Colorado 80401, USA
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Photovoltaic Research and Development (PVRD) Program
OSTI Identifier:
1456869
Report Number(s):
NREL/JA-5K00-71795
Journal ID: ISSN 0021-8979
DOE Contract Number:  
AC36-08GO28308
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 123; Journal Issue: 20; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; polycrystals; luminescence; transition metals; semiconductors; solar cells; photodetectors; crystal defects; electrical engineering; band gap

Citation Formats

Swanson, Drew E., Reich, Carey, Abbas, Ali, Shimpi, Tushar, Liu, Hanxiao, Ponce, Fernando A., Walls, John M., Zhang, Yong-Hang, Metzger, Wyatt K., Sampath, W. S., and Holman, Zachary C. CdCl 2 passivation of polycrystalline CdMgTe and CdZnTe absorbers for tandem photovoltaic cells. United States: N. p., 2018. Web. doi:10.1063/1.5023811.
Swanson, Drew E., Reich, Carey, Abbas, Ali, Shimpi, Tushar, Liu, Hanxiao, Ponce, Fernando A., Walls, John M., Zhang, Yong-Hang, Metzger, Wyatt K., Sampath, W. S., & Holman, Zachary C. CdCl 2 passivation of polycrystalline CdMgTe and CdZnTe absorbers for tandem photovoltaic cells. United States. doi:10.1063/1.5023811.
Swanson, Drew E., Reich, Carey, Abbas, Ali, Shimpi, Tushar, Liu, Hanxiao, Ponce, Fernando A., Walls, John M., Zhang, Yong-Hang, Metzger, Wyatt K., Sampath, W. S., and Holman, Zachary C. Mon . "CdCl 2 passivation of polycrystalline CdMgTe and CdZnTe absorbers for tandem photovoltaic cells". United States. doi:10.1063/1.5023811.
@article{osti_1456869,
title = {CdCl 2 passivation of polycrystalline CdMgTe and CdZnTe absorbers for tandem photovoltaic cells},
author = {Swanson, Drew E. and Reich, Carey and Abbas, Ali and Shimpi, Tushar and Liu, Hanxiao and Ponce, Fernando A. and Walls, John M. and Zhang, Yong-Hang and Metzger, Wyatt K. and Sampath, W. S. and Holman, Zachary C.},
abstractNote = {As single-junction silicon solar cells approach their theoretical limits, tandems provide the primary path to higher efficiencies. CdTe alloys can be tuned with magnesium (CdMgTe) or zinc (CdZnTe) for ideal tandem pairing with silicon. A II-VI/Si tandem holds the greatest promise for inexpensive, high-efficiency top cells that can be quickly deployed in the market using existing polycrystalline CdTe manufacturing lines combined with mature silicon production lines. Currently, all high efficiency polycrystalline CdTe cells require a chloride-based passivation process to passivate grain boundaries and bulk defects. This research examines the rich chemistry and physics that has historically limited performance when extending Cl treatments to polycrystalline 1.7-eV CdMgTe and CdZnTe absorbers. A combination of transmittance, quantum efficiency, photoluminescence, transmission electron microscopy, and energy-dispersive X-ray spectroscopy clearly reveals that during passivation, Mg segregates and out-diffuses, initially at the grain boundaries but eventually throughout the bulk. CdZnTe exhibits similar Zn segregation behavior; however, the onset and progression is localized to the back of the device. After passivation, CdMgTe and CdZnTe can render a layer that is reduced to predominantly CdTe electro-optical behavior. Contact instabilities caused by inter-diffusion between the layers create additional complications. The results outline critical issues and paths for these materials to be successfully implemented in Si-based tandems and other applications.},
doi = {10.1063/1.5023811},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 20,
volume = 123,
place = {United States},
year = {2018},
month = {5}
}

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