DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Distribution of Copper States, Phases, and Defects across the Depth of a Cu-Doped CdTe Solar Cell

Journal Article · · Chemistry of Materials
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1];  [1]; ORCiD logo [1]; ORCiD logo [3];  [4]; ORCiD logo [5];  [6];  [7]; ORCiD logo [8]; ORCiD logo [1]
  1. Arizona State University, Tempe, AZ (United States)
  2. Purdue University, West Lafayette, IN (United States); Argonne National Laboratory (ANL), Argonne, IL (United States). Center for Nanoscale Materials (CNM)
  3. National Renewable Energy Laboratory (NREL), Golden, CO (United States)
  4. First Solar, Perrysburg, OH (United States)
  5. Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany)
  6. Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
  7. Argonne National Laboratory (ANL), Argonne, IL (United States). Center for Nanoscale Materials (CNM); Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
  8. Argonne National Laboratory (ANL), Argonne, IL (United States). Center for Nanoscale Materials (CNM)

Copper has been used as a p-type dopant in cadmium telluride (CdTe) for decades. However, the density of Cu atoms in the finished device is much higher than that of holes, which means that most Cu atoms are not activated as acceptors during incorporation. Furthermore, studies have demonstrated that the distribution of copper (Cu) atoms across the device is highly inhomogeneous, with reports citing Cu substitution on Cd sites and segregation to grain boundaries. Fast diffusion along these boundaries and Cu accumulation at the CdTe/CdS interface have also been observed and validated computationally. These levels of inhomogeneity make it difficult to accurately characterize and correlate the performance with the nature of the Cu atomic species present. To address this challenge, we utilize X-ray microscopy and, specifically, nanoscale fluorescence-mode X-ray absorption near-edge structure to resolve the atomic Cu environment throughout the depth of the CdTe layer. Our results suggest that the majority of Cu atoms are in the form of CuxTe phases (or similar local environments) near the ZnTe|CdTe interface, CuxO phases in the CdTe absorber, and present in various oxidation states, including Cu1+ and Cu2+, near the CdS/CdTe junction. Here this work also provides experimental evidence for the first time of the presence of CuS around the ZnTe|CdTe interface and the hypothesized CuCd-Cli complex in the CdTe absorber.

Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States); National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office; USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
AC02-06CH11357; AC36-08GO28308; EE0008163; EE0008754
OSTI ID:
2281544
Report Number(s):
NREL/JA--5K00-86352; MainId:87125; UUID:5ff4909a-8dac-4daf-87f1-0a92892636d9; MainAdminID:71552
Journal Information:
Chemistry of Materials, Journal Name: Chemistry of Materials Journal Issue: 23 Vol. 35; ISSN 0897-4756
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

References (75)

Obtaining Large Columnar CdTe Grains and Long Lifetime on Nanocrystalline CdSe, MgZnO, or CdS Layers journal January 2018
Back contacts materials used in thin film CdTe solar cells—A review journal February 2021
Transactions and Communications journal May 1944
Role of oxygen during CdTe growth for CdTe photovoltaic devices: Role of oxygen during CdTe growth journal August 2014
Optimization of CdTe thin-film solar cell efficiency using a sputtered, oxygenated CdS window layer: Optimization of CdTe thin-film solar cell efficiency using a sputtered, oxygenated CdS window layer
  • Kephart, Jason M.; Geisthardt, Russell M.; Sampath, W. S.
  • Progress in Photovoltaics: Research and Applications, Vol. 23, Issue 11 https://doi.org/10.1002/pip.2578
journal January 2015
Solar cell efficiency tables (Version 60)
  • Green, Martin A.; Dunlop, Ewan D.; Hohl‐Ebinger, Jochen
  • Progress in Photovoltaics: Research and Applications, Vol. 30, Issue 7 https://doi.org/10.1002/pip.3595
journal June 2022
Copper migration in cdte heterojunction solar cells journal July 1996
The diffusion of copper in cadmium telluride journal February 1992
Conductivity anisotropy and structural phase transition in Covellite CuS journal February 1993
Correlation of surface phases with electrical behavior in thin-film CdTe devices journal May 2003
Stability of CdTe/CdS thin-film solar cells journal May 2000
Emerging inorganic compound thin film photovoltaic materials: Progress, challenges and strategies journal December 2020
In situ lift-out: Steps to improve yield and a comparison with other FIB TEM sample preparation techniques journal December 2008
Control of Cu doping and CdTe/Te interface modification for CdTe solar cells journal December 2017
Grain engineering: How nanoscale inhomogeneities can control charge collection in solar cells journal February 2017
The nanoscale distribution of copper and its influence on charge collection in CdTe solar cells journal January 2022
Quantitative analysis of Cu XANES spectra using linear combination fitting of binary mixtures simulated by FEFF9 journal January 2023
Bilayered ZnTe/Cu1.4Te alloy thin films as a back contact for CdTe solar cells journal June 2019
Copper inclusion and migration from the back contact in CdTe solar cells journal March 2004
Nanoscale doping profiles within CdTe grain boundaries and at the CdS/CdTe interface revealed by atom probe tomography and STEM EBIC journal June 2016
Comparative study of As and Cu doping stability in CdSeTe absorbers journal June 2021
Cu K-edge X-ray fine structure changes in CdTe with CdCl2 processing journal June 2005
Phase control of CuxTe film and its effects on CdS/CdTe solar cell journal May 2007
The formation of different phases of CuxTe and their effects on CdTe/CdS solar cells journal June 2007
Cu-related recombination in CdS/CdTe solar cells journal February 2008
First-principles-based analysis of the influence of Cu on CdTe electronic properties journal May 2013
Identification and Quantification of Chemical Forms of Cu and Zn in MSWI Ashes Using XANES journal September 2020
Passivating Grain Boundaries in Polycrystalline CdTe journal September 2019
Doping of polycrystalline CdTe for high-efficiency solar cells on flexible metal foil journal August 2013
CdTe solar cells with open-circuit voltage breaking the 1 V barrier journal February 2016
Charge transport in CdTe solar cells revealed by conductive tomographic atomic force microscopy journal September 2016
Machine-learned impurity level prediction for semiconductors: the example of Cd-based chalcogenides journal April 2020
Defect interactions and the role of complexes in the CdTe solar cell absorber journal January 2017
Controlled growth of metallic copper nanoparticles journal January 2017
Parameter-free calculations of X-ray spectra with FEFF9 journal January 2010
Photoluminescence of Cu-doped CdTe and related stability issues in CdS/CdTe solar cells journal September 2000
Some Diffusion and Solubility Measurements of Cu in CdTe journal November 1968
Detailed Balance Limit of Efficiency of p‐n Junction Solar Cells journal March 1961
Cu and CdCl2 influence on defects detected in CdTe solar cells with admittance spectroscopy journal October 2005
Stability and electronic structures of CuxTe journal August 2007
A comprehensive picture of Cu doping in CdTe solar cells journal November 2013
First-principles study of roles of Cu and Cl in polycrystalline CdTe journal January 2016
Long carrier lifetimes in large-grain polycrystalline CdTe without CdCl2 journal June 2016
The roles of carrier concentration and interface, bulk, and grain-boundary recombination for 25% efficient CdTe solar cells journal June 2017
Grain boundaries in CdTe thin film solar cells: a review journal July 2016
The 2020 photovoltaic technologies roadmap journal September 2020
On the stability of Cu x Te polytypes: phase transitions, vibrational and electronic properties journal October 2019
Diffusion in CdS of Cd and S vacancies and Cu, Cd, Cl, S and Te interstitials studied with first-principles computations journal May 2014
Defect activation and annihilation in CIGS solar cells: an operando x-ray microscopy study journal February 2020
Chemical trends of defect formation and doping limit in II-VI semiconductors: The case of CdTe journal October 2002
Density-functional electronic structure calculations for native defects and Cu impurities in CdS journal July 2006
ATHENA , ARTEMIS , HEPHAESTUS : data analysis for X-ray absorption spectroscopy using IFEFFIT journal June 2005
Multimodal X-ray imaging of grain-level properties and performance in a polycrystalline solar cell journal May 2019
Electrical Characterization of Cu Composition Effects in CdS/CdTe Thin-Film Solar Cells With a ZnTe:Cu Back Contact journal July 2013
CdTe Solar Cells at the Threshold to 20% Efficiency journal October 2013
Strain Mapping of CdTe Grains in Photovoltaic Devices journal November 2019
Modeling Cu migration in CdTe solar cells under device-processing and long-term stability conditions conference May 2008
Unraveling Cu chemical signature in CdTe by Spectral Fluorescence Mapping conference June 2021
Cu-Local Structures and Their Relation with Nanoscale Electrical Performance in CdTe conference June 2020
Transient Ion Drift Measurements of Polycrystalline CdTe PV Devices
  • Enzenroth, R. A.; Barth, K. L.; Sampath, W. S.
  • Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, 2006 IEEE 4th World Conference on Photovoltaic Energy Conference https://doi.org/10.1109/WCPEC.2006.279487
conference May 2006
Role of Copper in the Performance of CdS/CdTe Solar Cells conference January 2006
The Distribution of the Flora in the Alpine Zone.1 journal February 1912
Copper-induced recrystallization and interdiffusion of CdTe/ZnTe thin films
  • Samoilenko, Yegor; Abbas, Ali; Michael Walls, J.
  • Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, Vol. 36, Issue 3 https://doi.org/10.1116/1.5023501
journal May 2018
Growth of CdTe films by close‐spaced vapor transport
  • Anthony, Thomas C.; Fahrenbruch, Alan L.; Bube, Richard H.
  • Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, Vol. 2, Issue 3 https://doi.org/10.1116/1.572398
journal July 1984
Development of Cu‐doped ZnTe as a back‐contact interface layer for thin‐film CdS/CdTe solar cells
  • Gessert, T. A.; Mason, A. R.; Sheldon, P.
  • Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, Vol. 14, Issue 3 https://doi.org/10.1116/1.580394
journal May 1996
High-sensitivity nanoscale chemical imaging with hard x-ray nano-XANES journal September 2020
Speciation using X-ray absorption fine structure (XAFS) journal October 2015
Solving Least Squares Problems book January 1995
Effects of Cu on CdTe∕CdS Heterojunction Solar Cells with Au/Cu Contacts journal January 1995
XAFS for Everyone book May 2013
Cu K-edge XAFS in CdTe before and after treatment with CdCl2 journal January 2003
Engineering solar cells based on correlative X-ray microscopy journal May 2017
Exploring Back Contact Technology to Increase CdS/CdTe Solar Cell Efficiency journal January 2007
Review of the CdCl2 Treatment Used in CdS/CdTe Thin Film Solar Cell Development and New Evidence towards Improved Understanding journal April 2014
X-ray Beam Induced Current Measurements for Multi-Modal X-ray Microscopy of Solar Cells journal January 2019