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Title: Polycrystalline Thin Film Device Degradation Studies

Abstract

Oxygen during vapor CdCl2 (VCC) treatments significantly reduced resistive shunts observed in CdS/CdTe polycrystalline devices using thinner CdS layers during 100 deg C, open-circuit, 1-sun accelerated stress testing. Cu oxidation resulting from the reduction of various trace oxides present in as-grown and VCC treated films is the proposed mechanism by which Cu diffusion, and subsequent shunts are controlled. Graphite paste layers between metallization and CdTe behave like diffusion barriers and similarly benefit device stability. Ni-based contacts form a protective Ni2Te3 intermetallic layer that reduces metal diffusion but degrades performance through increased series resistance.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
882806
Report Number(s):
NREL/CP-520-39003
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Conference
Resource Relation:
Related Information: Presented at the 2005 DOE Solar Energy Technologies Program Review Meeting held November 7-10, 2005 in Denver, Colorado. Also included in the proceedings available on CD-ROM (DOE/GO-1020060-2245; NREL/CD-520-38577)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; PHOTOVOLTAICS; SOLAR; POLYCRYSTALLINE; THIN FILM; PV; NREL; Solar Energy - Photovoltaics

Citation Formats

Albin, D. S., McMahon, T. J., Pankow, J. W., Noufi, R., Demtsu, S. H., and Davies, A. Polycrystalline Thin Film Device Degradation Studies. United States: N. p., 2005. Web.
Albin, D. S., McMahon, T. J., Pankow, J. W., Noufi, R., Demtsu, S. H., & Davies, A. Polycrystalline Thin Film Device Degradation Studies. United States.
Albin, D. S., McMahon, T. J., Pankow, J. W., Noufi, R., Demtsu, S. H., and Davies, A. Tue . "Polycrystalline Thin Film Device Degradation Studies". United States. doi:. https://www.osti.gov/servlets/purl/882806.
@article{osti_882806,
title = {Polycrystalline Thin Film Device Degradation Studies},
author = {Albin, D. S. and McMahon, T. J. and Pankow, J. W. and Noufi, R. and Demtsu, S. H. and Davies, A.},
abstractNote = {Oxygen during vapor CdCl2 (VCC) treatments significantly reduced resistive shunts observed in CdS/CdTe polycrystalline devices using thinner CdS layers during 100 deg C, open-circuit, 1-sun accelerated stress testing. Cu oxidation resulting from the reduction of various trace oxides present in as-grown and VCC treated films is the proposed mechanism by which Cu diffusion, and subsequent shunts are controlled. Graphite paste layers between metallization and CdTe behave like diffusion barriers and similarly benefit device stability. Ni-based contacts form a protective Ni2Te3 intermetallic layer that reduces metal diffusion but degrades performance through increased series resistance.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Nov 01 00:00:00 EST 2005},
month = {Tue Nov 01 00:00:00 EST 2005}
}

Conference:
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  • The correlation of stress-induced changes in the performance of laboratory-made CdTe solar cells with various 2nd and 3rd level metrics is discussed. The overall behavior of aggregated data showing how cell efficiency changes as a function of open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) is explained using a two-diode, PSpice model in which degradation is simulated by systematically changing model parameters. FF shows the highest correlation with performance during stress, and is subsequently shown to be most affected by shunt resistance, recombination and in some cases voltage-dependent collection. Large decreases in Jsc as well as increasingmore » rates of Voc degradation are related to voltage-dependent collection effects and catastrophic shunting respectively. Large decreases in Voc in the absence of catastrophic shunting are attributed to increased recombination. The relevance of capacitance-derived data correlated with both Voc and FF is discussed.« less
  • Recent results from the United States Department of Energy (DOE) Thin-Film Photovoltaic Device Program are presented. The program which is managed by the Solar Energy Research Institute (SERI) encompasses materials and device research on highly absorbing compound semiconductors including cuInSe/sub 2/, CdTe, Cu /SUB 2-x/ Se, Zn/sub 3/P/sub 2/, ZnSiAs/sub 2/, and Cu/sub 2/S. Excitement in the program has been generated by recent progress in the (Cd,Zn)S/ CuInSe/sub 2/ device area where an efficiency of 10.6% on a 5 ..mu..m thick device has been reported. Other highlights include deposition of a hybrid CdS/Cu/sub 2/S device (evaporated CdS, sputtered Cu/sub 2/S)more » with a 7.1% AM1 efficiency, and of a 3.94% AM1 efficiency all-sputtered CdS/Cu/sub 2/S cell. AM1 efficiencies exceeding 5% are reported for CdTe Schottky barrier and heterojunction devices, and for a CdS/Cu /SUB 2-x/ Se heterojunction. AM1 efficiencies exceeding 4% are reported for Mg/Zn/sub 3/P/sub 2/ Schottky barrier cells. Future research emphasis is outlined.« less
  • The general purpose of the workshop was to accelerate the development of thin film solar cells by improving the versatility and reliability of material and device measurement techniques. Papers were presented under the following sessions: structural/chemical session; optical/electro-optical session; charge transport session; and poster session. Each paper was processed for EDB.
  • Recent results from the United States Department of Energy (DOE) Thin-Film Photovoltaic Device Program are presented. The program encompasses materials and device research on highly absorbing compound semiconductors including CuInSe/sub 2/, CdTe, Cu/sub 2-x/Se, Zn/sub 3/P/sub 2/, ZnSiAs/sub 2/, and Cu/sub 2/S. Excitement in the program has been generated by recent progress in the (Cd,Zn)S/CuInSe/sub 2/ device area where an efficiency of 10.6% on a 5 ..mu..m thick device has been reported. Other highlights include deposition of a hybrid CdS/Cu/sub 2/S device (evaporated CdS, sputtered Cu/sub 2/S) with a 7.1% AM1 efficiency, and of a 3.94% AM1 efficiency all-sputtered CdS/Cu/submore » 2/S cell. AM1 efficiencies exceeding 5% are reported for CdTe Schottky barrier and heterojunction devices, and for a CdS/Cu/sub 2-x/Se heterojunction. AM1 efficiencies exceeding 4% are reported for Mg/Zn/sub 3/P/sub 2/ Schottky barrier cells. Future research emphasis is outlined.« less
  • A new data mining algorithm was developed to identify the strongest correlations between capacitance data (measured between -1.5 V and +0.49 V) and 1st and 2nd level performance metrics (efficiency, open-circuit voltage (VOC), short-circuit current density (JSC), and fill-factor (FF)) during the stress testing of voltage-stabilized CdS/CdTe devices. When considering only correlations between 1st and 2nd level metrics, 96.5% of the observed variation in efficiency was attributed to FF. The overall decrease in VOC after 1000 hours of open-circuit, light-soak stress at 60 degrees C was about 1.5%. As determined by our algorithm, the most consistent correlation existing between FFmore » and 3rd level metric capacitance data at all stages during stress testing was between FF and the apparent CdTe acceptor density (Na) calculated at a voltage of +0.49 V during forward voltage scans. Since the contribution of back contact capacitance to total capacitance increases with increasing positive voltage, this result suggests that FF degradation is associated with decreases in Na near the CdTe/back contact interface. Also of interest, it appears that capacitance data at these higher voltages appears to more accurately fit the one-sided abrupt junction model.« less