skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Cathodoluminescence spectrum imaging analysis of CdTe thin-film bevels

Abstract

We conducted T = 6 K cathodoluminescence (CL) spectrum imaging with a nanoscale electron beam on beveled surfaces of CdTe thin films at the critical stages of standard CdTe solar cell fabrication. We find that the through-thickness CL total intensity profiles are consistent with a reduction in grain-boundary recombination due to the CdCl2 treatment. The color-coded CL maps of the near-band-edge transitions indicate significant variations in the defect recombination activity at the micron and sub-micron scales within grains, from grain to grain, throughout the film depth, and between films with different processing histories. We estimated the grain-interior sulfur-alloying fraction in the interdiffused CdTe/CdS region of the CdCl2-treated films from a sample of 35 grains and found that it is not strongly correlated with CL intensity. A kinetic rate-equation model was used to simulate grain-boundary (GB) and grain-interior CL spectra. Simulations indicate that the large reduction in the exciton band intensity and relatively small decrease in the lower-energy band intensity at CdTe GBs or dislocations can be explained by an enhanced electron-hole non-radiative recombination rate at the deep GB or dislocation defects. Simulations also show that higher GB concentrations of donors and/or acceptors can increase the lower-energy band intensity, while slightlymore » decreasing the exciton band intensity.« less

Authors:
 [1];  [2];  [2];  [2];  [2];  [1];  [2]
  1. National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, USA; Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, USA
  2. National Renewable Energy Laboratory, 15013 Denver West Parkway, 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)
OSTI Identifier:
1326326
Report Number(s):
NREL/JA-5K00-66565
Journal ID: ISSN 0021-8979
DOE Contract Number:
AC36-08GO28308
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 120; Journal Issue: 10
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; catholuminescence; excitons; II-VI semiconductors; geographic information systems; dislocations

Citation Formats

Moseley, John, Al-Jassim, Mowafak M., Guthrey, Harvey L., Burst, James M., Duenow, Joel N., Ahrenkiel, Richard K., and Metzger, Wyatt K. Cathodoluminescence spectrum imaging analysis of CdTe thin-film bevels. United States: N. p., 2016. Web. doi:10.1063/1.4962286.
Moseley, John, Al-Jassim, Mowafak M., Guthrey, Harvey L., Burst, James M., Duenow, Joel N., Ahrenkiel, Richard K., & Metzger, Wyatt K. Cathodoluminescence spectrum imaging analysis of CdTe thin-film bevels. United States. doi:10.1063/1.4962286.
Moseley, John, Al-Jassim, Mowafak M., Guthrey, Harvey L., Burst, James M., Duenow, Joel N., Ahrenkiel, Richard K., and Metzger, Wyatt K. 2016. "Cathodoluminescence spectrum imaging analysis of CdTe thin-film bevels". United States. doi:10.1063/1.4962286.
@article{osti_1326326,
title = {Cathodoluminescence spectrum imaging analysis of CdTe thin-film bevels},
author = {Moseley, John and Al-Jassim, Mowafak M. and Guthrey, Harvey L. and Burst, James M. and Duenow, Joel N. and Ahrenkiel, Richard K. and Metzger, Wyatt K.},
abstractNote = {We conducted T = 6 K cathodoluminescence (CL) spectrum imaging with a nanoscale electron beam on beveled surfaces of CdTe thin films at the critical stages of standard CdTe solar cell fabrication. We find that the through-thickness CL total intensity profiles are consistent with a reduction in grain-boundary recombination due to the CdCl2 treatment. The color-coded CL maps of the near-band-edge transitions indicate significant variations in the defect recombination activity at the micron and sub-micron scales within grains, from grain to grain, throughout the film depth, and between films with different processing histories. We estimated the grain-interior sulfur-alloying fraction in the interdiffused CdTe/CdS region of the CdCl2-treated films from a sample of 35 grains and found that it is not strongly correlated with CL intensity. A kinetic rate-equation model was used to simulate grain-boundary (GB) and grain-interior CL spectra. Simulations indicate that the large reduction in the exciton band intensity and relatively small decrease in the lower-energy band intensity at CdTe GBs or dislocations can be explained by an enhanced electron-hole non-radiative recombination rate at the deep GB or dislocation defects. Simulations also show that higher GB concentrations of donors and/or acceptors can increase the lower-energy band intensity, while slightly decreasing the exciton band intensity.},
doi = {10.1063/1.4962286},
journal = {Journal of Applied Physics},
number = 10,
volume = 120,
place = {United States},
year = 2016,
month = 9
}
  • Cited by 2
  • We conduct T=6 K cathodoluminescence (CL) spectrum imaging with a nano-scale electron beam on beveled surfaces of CdTe thin-films at different critical stages of standard CdTe device fabrication. The through-thickness total CL intensity profiles are consistent with a reduction in grain boundary recombination due to the CdCl2 treatment. Color-coded maps of the low-temperature luminescence transition energies reveal that CdTe thin films have remarkably non-uniform opto-electronic properties, which depend strongly on sample processing history. The grain-to-grain S content in the interdiffused CdTe/CdS region is estimated from a sample size of thirty-five grains, and the S content in adjacent grains varies significantlymore » in CdCl2-treated samples. A low-temperature luminescence model is developed to interpret spectral behavior at grain boundaries and grain interiors.« less
  • Cerium doped lutetium orthosilicate thin films were sputter deposited onto rough and smooth alumina substrates to compare their extrinsic photoluminescence efficiency. To understand the photoluminescence results, scanning electron and cathodoluminescence imaging were performed. The plane view and cross-section images revealed that dark cathodoluminescence regions were correlated with topology in both films, though the mechanisms for the degraded luminescence were different. For the rough films, substrate topology causes localized shadowing of the sputtered species which creates compositional inhomogeneities. The smooth films have protrusions caused by thermally induced stress and the reduced cathodoluminescence intensity is attributed to electron-hole surface recombination.
  • Purpose: The authors investigate performance of thin-film cadmium telluride (CdTe) in detecting high-energy (6 MV) x rays. The utilization of this material has become technologically feasible only in recent years due to significant development in large area photovoltaic applications. Methods: The CdTe film is combined with a metal plate, facilitating conversion of incoming photons into secondary electrons. The system modeling is based on the Monte Carlo simulations performed to determine the optimized CdTe layer thickness in combination with various converter materials. Results: The authors establish a range of optimal parameters producing the highest DQE due to energy absorption, as wellmore » as signal and noise spatial spreading. The authors also analyze the influence of the patient scatter on image formation for a set of detector configurations. The results of absorbed energy simulation are used in device operation modeling to predict the detector output signal. Finally, the authors verify modeling results experimentally for the lowest considered device thickness. Conclusions: The proposed CdTe-based large area thin-film detector has a potential of becoming an efficient low-cost electronic portal imaging device for radiation therapy applications.« less