The nanoscale distribution of copper and its influence on charge collection in CdTe solar cells

Trumann Walker, Michael E. Stuckelberger, Tara Nietzold, Niranjana Mohan-Kumar, Christina Ossig, Maik Kahnt, Felix Wittwer, Barry Lai, Damien Salomon, Eric Colegrove, Mariana I. Bertoni

Research output: Contribution to journalArticlepeer-review

Abstract

For decades, Cu has been the primary dopant in CdTe photovoltaic absorbers. Typically, Cu acceptor concentrations in these devices are on the order of 1 × 1014 cm−3, which has made it notoriously difficult to directly correlate nanoscale Cu distributions to the local charge transport properties of these devices. To measure and correlate these properties, measurement techniques require high sensitivity to elemental concentration, large penetration depth, and operando compatibility. Techniques such as secondary-ion mass spectroscopy and X-ray energy dispersive spectroscopy are widely adopted to measure Cu concentrations, but they are limited by penetration depth, sensitivity, or spatial resolution. Additionally, they lack the operando capabilities required to correlate one-to-one Cu concentrations to electrical performance. In this work, correlative X-ray microscopy is used to investigate the spatial distribution of Cu and its impact on charge collection through the depth and breadth of CdTe photovoltaic devices. Plan-view, nanoscale X-ray fluorescence maps clearly demonstrate the spatial segregation of copper around regions thought to be CdTe grain boundaries. Complementary cross-section imaging unveils the transition of the maximum charge-collection efficiency from the ZnTe–CdTe interface to the CdS–CdTe interface as a function of Cu incorporation. The copper concentration through the depth of the CdTe layer is characterized by slow and fast diffusion components, and cross-section charge-transport modeling shows that the experimentally obtained charge collection can be explained by the modeled acceptor distribution through the depth of the CdTe layer.

Original languageEnglish
Article number106595
JournalNano Energy
Volume91
DOIs
Publication statusPublished - 2022 Jan
Externally publishedYes

Bibliographical note

Funding Information:
This material is based on the work supported by the Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy Solar Energy Technologies under contract No. DE-EE0008163 and DE-EE0008754. This work was authored in part by Alliance for Sustainable Energy, LLC, the manager and operator of the National Renewable Energy Laboratory for the U.S. DOE under Contract No. DE-AC36-08GO28308. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The views expressed in this article do not necessarily represent the views of the DOE or the U.S. Government. The publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes. Part of the experiments were performed on beamline ID16B at the European Synchrotron Radiation Facility (ESRF), Grenoble, France. We are grateful to Remi Tucoulou Tachoueres, Julie Villanova, and Jaime Segura Ruiz at the ESRF for providing assistance in using beamline ID16B and supporting data analysis. This research received funding from DESY and was supported through the European XFEL and DESY funded Maxwell computational resources. The authors thank Abdul R. Shaik for invaluable help modifying the PyCDTS simulator to model cross-section illumination and providing instruction on the use and output of the software. We are also grateful to Andr? Rothkirch and Frank Schl?nzen (both DESY) for adapting PyMCA to run on Maxwell.

Funding Information:
Part of the experiments were performed on beamline ID16B at the European Synchrotron Radiation Facility (ESRF), Grenoble, France. We are grateful to Remi Tucoulou Tachoueres, Julie Villanova, and Jaime Segura Ruiz at the ESRF for providing assistance in using beamline ID16B and supporting data analysis. This research received funding from DESY and was supported through the European XFEL and DESY funded Maxwell computational resources.

Funding Information:
This material is based on the work supported by the Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy Solar Energy Technologies under contract No. DE-EE0008163 and DE-EE0008754 . This work was authored in part by Alliance for Sustainable Energy, LLC, the manager and operator of the National Renewable Energy Laboratory for the U.S. DOE under Contract No. DE-AC36-08GO28308 . This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357 . The views expressed in this article do not necessarily represent the views of the DOE or the U.S. Government. The publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.

Publisher Copyright:
© 2021 Elsevier Ltd

Keywords

  • CdTe doping
  • Charge collection
  • Copper diffusion
  • X-ray beam induced current
  • X-ray fluorescence

Fingerprint

Dive into the research topics of 'The nanoscale distribution of copper and its influence on charge collection in CdTe solar cells'. Together they form a unique fingerprint.

Cite this