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Title: Analysis of CdS/CdTe Devices Incorporating a ZnTe:Cu/Ti Contact

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
908623
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Conference
Resource Relation:
Conference: Thin Solid Films; Proceedings of Symposium O on Thin Film Chalcogenide Photovoltaic Materials, EMRS 2006 Conference; 29 May - 2 June 2006, Nice, France
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; CHALCOGENIDES; THIN FILMS; PHOTOVOLTAIC CELLS; SPUTTERING; TARGETS; MATERIALS; Solar Energy - Photovoltaics

Citation Formats

Gessert, T. A., Asher, S., Johnston, S., Young, M., Dippo, P., and Corwine, C.. Analysis of CdS/CdTe Devices Incorporating a ZnTe:Cu/Ti Contact. United States: N. p., 2007. Web.
Gessert, T. A., Asher, S., Johnston, S., Young, M., Dippo, P., & Corwine, C.. Analysis of CdS/CdTe Devices Incorporating a ZnTe:Cu/Ti Contact. United States.
Gessert, T. A., Asher, S., Johnston, S., Young, M., Dippo, P., and Corwine, C.. Mon . "Analysis of CdS/CdTe Devices Incorporating a ZnTe:Cu/Ti Contact". United States. doi:.
@article{osti_908623,
title = {Analysis of CdS/CdTe Devices Incorporating a ZnTe:Cu/Ti Contact},
author = {Gessert, T. A. and Asher, S. and Johnston, S. and Young, M. and Dippo, P. and Corwine, C.},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • We study the performance of CdS/CdTe thin-film devices contacted with ZnTe:Cu/Ti of various thickness at a higher-than-optimum temperature of {approx}360 C. At this temperature, optimum device performance requires the same thickness of ZnTe:Cu as for similar contacts formed at a lower temperature of 320 C. C-V analysis indicates that a ZnTe:Cu layer thickness of {approx}< 0.5 mu m does not yield the degree of CdTe net acceptor concentration necessary to reduce space charge width to its optimum value for n-p device operation. The thickest ZnTe:Cu layer investigated (1 mu m) yields the highest CdTe net acceptor concentration, lowest value ofmore » Jo, and highest Voc. However, performance is limited for this device by poor fill factor. We suggest poor fill factor is due to Cu-related acceptors compensating donors in CdS.« less
  • The conclusions of this report are that Cu diffusion from a ZnTe:Cu contact causes good and bad things. The good (Cu in CdS < low 10{sup 18} cm{sup -3})--increase in CdTe N{sub A}-N{sub D} that leads to V{sub oc} and FF improvement. The bad (Cu in CdS > low 10{sup 18} cm{sup -3})--(1) possibly decreased of shunt resistance (?); (2) depletion width in CdTe can become too narrow for optimum current collection at J{sub MPP}; (3) donor reduction in CdS (significant FF loss in LIV); and (4) excessive Cu diffusion into CdS readily observed by red-light bias QE.
  • We study the performance of CdS/CdTe thin-film devices contacted with ZnTe:Cu/Ti of various thickness at a higher-than-optimum temperature of {approx}360 C. At this temperature, optimum device performance requires the same thickness of ZnTe:Cu as for similar contacts formed at a lower temperature of 320 C. C-V analysis indicates that a ZnTe:Cu layer thickness of < {approx}0.5 mum does not yield the degree of CdTe net acceptor concentration necessary to reduce space charge width to its optimum value for n-p device operation. The thickest ZnTe:Cu layer investigated (1mum) yields the highest CdTe net acceptor concentration, lowest value of J{sub o}, andmore » highest V{sub oc}. However, performance is limited for this device by poor fill factor. We suggest poor fill factor is due to Cu-related acceptors compensating donors in CdS.« less
  • We report on the recent use of cathodoluminescence (CL) to probe the depth-dependent changes in radiative recombination that occur in CdTe devices during ZnTe:Cu contacting procedures. These types of CL measurements may be useful to assist in linking impurity diffusion (e.g., Cu) from the contact with depth-dependent variation in electrical activation within the CdTe layer. Variable-energy CL suggests that diffusion from the ZnTe:Cu contact interface may assist in reducing donors levels in the CdTe bulk, and thereby yield p-type material in the region near the contact. CL analysis near abrupt metal discontinuities provides estimates of diffusion lengths for carriers associatedmore » with both excitonic and donor-to-acceptor pair recombination. Finally, CL measurements at increasing excitation levels (i.e., increasing electron-beam current) provides estimates of the defect state density, as well as providing evidence that discrete multiple defect bands may exist in CdTe prior to contacting.« less