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Title: Two-Dimensional Cadmium Chloride Nanosheets in Cadmium Telluride Solar Cells

Abstract

In this paper we make use of a liquid nitrogen-based thermomechanical cleavage technique and a surface analysis cluster tool to probe in detail the tin oxide/emitter interface at the front of completed CdTe solar cells. We show that this thermomechanical cleavage occurs within a few angstroms of the SnO 2/emitter interface. An unexpectedly high concentration of chlorine at this interface, ~20%, was determined from a calculation that assumed a uniform chlorine distribution. Angle-resolved X-ray photoelectron spectroscopy was used to further probe the structure of the chlorine-containing layer, revealing that both sides of the cleave location are covered by one-third of a unit cell of pure CdCl 2, a thickness corresponding to about one Cl-Cd-Cl molecular layer. We interpret this result in the context of CdCl 2 being a true layered material similar to transition-metal dichalcogenides. Exposing cleaved surfaces to water shows that this Cl-Cd-Cl trilayer is soluble, raising questions pertinent to cell reliability. Our work provides new and unanticipated details about the structure and chemistry of front surface interfaces and should prove important to improving materials, processes, and reliability of next-generation CdTe-based solar cells.

Authors:
ORCiD logo [1];  [1];  [1];  [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1369128
Report Number(s):
NREL/JA-5K00-68533
Journal ID: ISSN 1944-8244; TRN: US1701990
Grant/Contract Number:
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Volume: 9; Journal Issue: 24; Journal ID: ISSN 1944-8244
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; cadmium chloride; cadmium telluride; nanosheets; solar cells; XPS

Citation Formats

Perkins, Craig L., Beall, Carolyn, Reese, Matthew O., and Barnes, Teresa M. Two-Dimensional Cadmium Chloride Nanosheets in Cadmium Telluride Solar Cells. United States: N. p., 2017. Web. doi:10.1021/acsami.7b03671.
Perkins, Craig L., Beall, Carolyn, Reese, Matthew O., & Barnes, Teresa M. Two-Dimensional Cadmium Chloride Nanosheets in Cadmium Telluride Solar Cells. United States. doi:10.1021/acsami.7b03671.
Perkins, Craig L., Beall, Carolyn, Reese, Matthew O., and Barnes, Teresa M. Fri . "Two-Dimensional Cadmium Chloride Nanosheets in Cadmium Telluride Solar Cells". United States. doi:10.1021/acsami.7b03671. https://www.osti.gov/servlets/purl/1369128.
@article{osti_1369128,
title = {Two-Dimensional Cadmium Chloride Nanosheets in Cadmium Telluride Solar Cells},
author = {Perkins, Craig L. and Beall, Carolyn and Reese, Matthew O. and Barnes, Teresa M.},
abstractNote = {In this paper we make use of a liquid nitrogen-based thermomechanical cleavage technique and a surface analysis cluster tool to probe in detail the tin oxide/emitter interface at the front of completed CdTe solar cells. We show that this thermomechanical cleavage occurs within a few angstroms of the SnO2/emitter interface. An unexpectedly high concentration of chlorine at this interface, ~20%, was determined from a calculation that assumed a uniform chlorine distribution. Angle-resolved X-ray photoelectron spectroscopy was used to further probe the structure of the chlorine-containing layer, revealing that both sides of the cleave location are covered by one-third of a unit cell of pure CdCl2, a thickness corresponding to about one Cl-Cd-Cl molecular layer. We interpret this result in the context of CdCl2 being a true layered material similar to transition-metal dichalcogenides. Exposing cleaved surfaces to water shows that this Cl-Cd-Cl trilayer is soluble, raising questions pertinent to cell reliability. Our work provides new and unanticipated details about the structure and chemistry of front surface interfaces and should prove important to improving materials, processes, and reliability of next-generation CdTe-based solar cells.},
doi = {10.1021/acsami.7b03671},
journal = {ACS Applied Materials and Interfaces},
number = 24,
volume = 9,
place = {United States},
year = {Fri May 12 00:00:00 EDT 2017},
month = {Fri May 12 00:00:00 EDT 2017}
}

Journal Article:
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  • Polycrystalline n-CdS/p-CdTe solar cells with a commercial carbon paint on the p-CdTe layer and an In- Ag paint on the n-CdS layer were fabricated by a coating and sintering method. Electrical properties of the conducting paints and solar cell parameters of the heterojunction solar cells were investigated as a function of electrode annealing conditions. The sintered CdS/CdTe solar cells whose electrode contacts were annealed at 350{degrees}C for 10 min in nitrogen showed maximum values of short-circuit current density, fill factor, and solar efficiency. Commercial carbon and silver paints can be used as electrodes to fabricate sintered CdS/CdTe solar cells withmore » efficiency over 10%.« less
  • We report on the development of a low-cost, thin-film electrodeposited cadmium telluride solar cell. The most efficient cell developed to date had an efficiency of 8.6% (under AM1 illumination), an open circuit voltage of 0.723 V, a short circuit current density of 18.7 mA/cm/sup 2/, and a fill factor of 0.64. The cell uses a Schottky barrier rectifying junction at the front surface and a cadmium ohmic contact at the back. Passivation of the top surface improves the photovoltaic properties of the rectifying junction.
  • An investigation was made of the physical processes occurring in photoelectrochemical conversion of solar energy by a CdTe--electrolyte junction involving surface exciton and electron states. The influence of these processes on the efficiency of conversion of solar energy into chemical energy of hydrogen was analyzed.
  • Solar cells have been fabricated by reactive deposition of thin-film n-In/sub 2/O/sub 3/ onto single-crystal p-CdTe. The cell has a total area solar power conversion efficiency of 13.4% which corresponds to an active area efficiency of 14.4% at air mass 1.5 without antireflection coatings. The cell consists of a buried homojunction structure with low dark saturation current density.
  • Deposition of cadmium telluride (CdTe) films on steel foil substrates was investigated. Adherent CdTe films were vacuum evaporated and a growth rate of 3 nm/sec was obtained at a substrate temperature of 533 K. As deposited films exhibited a preferred (111) orientation. A tellurium interlayer between CdTe and steel yielded larger grains in CdTe than a gold interlayer. Annealing of CdTe films at 823 K increased the grain size and reduced the film resistance; it also tended to transform p-type CdTe into n-type. This was attributed to the diffusion of tellurium from CdTe into steel and diffusion of iron frommore » the steel substrate into the CdTe film. This diffusion was observed using energy dispersive X-ray analysis. A photovoltage was obtained by depositing CdS on top of p-CdTe and a V{sub oc} of 360 mV was obtained. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}« less