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Title: Application of Single Wall Carbon Nanotubes as Transparent Electrodes in Cu(In,Ga)Se2-Based Solar Cells: Preprint

Abstract

We present a new thin-film solar cell structure in which the traditional transparent conductive oxide electrode (ZnO) is replaced by a transparent conductive coating consisting of a network of bundled single-wall carbon nanotubes. Optical transmission properties of these coatings are presented in relation to their electrical properties (sheet resistance), along with preliminary solar cell results from devices made using CuIn1-xGaxSe2 thin-film absorber materials. Achieving an energy conversion efficiency of >12% and a quantum efficiency of {approx}80% demonstrate the feasibility of the concept. A discussion of the device structures will be presented considering the physical properties of the new electrodes comparing current-voltage results from the new solar cell structure and those from standard ZnO/CdS/Cu(In,Ga)Se2/Mo solar cells.

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
891545
Report Number(s):
NREL/CP-520-39914
TRN: US200622%%87
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Conference
Resource Relation:
Conference: Presented at the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion (WCPEC-4), 7-12 May 2006, Waikoloa, Hawaii
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; CARBON; COATINGS; EFFICIENCY; ELECTRICAL PROPERTIES; ELECTRODES; ENERGY CONVERSION; NANOTUBES; OXIDES; PHYSICAL PROPERTIES; QUANTUM EFFICIENCY; SOLAR CELLS; CARBON NANOTUBES; TRANSPARENT CONDUCTIVE OXIDE (TCO); THIN FILM; ENERGY CONVERSION EFFICIENCY; DEVICE; FREE CARRIER CONCENTRATION; Solar Energy - Photovoltaics

Citation Formats

Contreras, M., Barnes, T., van de Lagemaat, J., Rumbles, G., Coutts, T. J., Weeks, C., Glatkowski, P., Levitsky, I., and Peltola, J.. Application of Single Wall Carbon Nanotubes as Transparent Electrodes in Cu(In,Ga)Se2-Based Solar Cells: Preprint. United States: N. p., 2006. Web. doi:10.1109/WCPEC.2006.279481.
Contreras, M., Barnes, T., van de Lagemaat, J., Rumbles, G., Coutts, T. J., Weeks, C., Glatkowski, P., Levitsky, I., & Peltola, J.. Application of Single Wall Carbon Nanotubes as Transparent Electrodes in Cu(In,Ga)Se2-Based Solar Cells: Preprint. United States. doi:10.1109/WCPEC.2006.279481.
Contreras, M., Barnes, T., van de Lagemaat, J., Rumbles, G., Coutts, T. J., Weeks, C., Glatkowski, P., Levitsky, I., and Peltola, J.. Mon . "Application of Single Wall Carbon Nanotubes as Transparent Electrodes in Cu(In,Ga)Se2-Based Solar Cells: Preprint". United States. doi:10.1109/WCPEC.2006.279481. https://www.osti.gov/servlets/purl/891545.
@article{osti_891545,
title = {Application of Single Wall Carbon Nanotubes as Transparent Electrodes in Cu(In,Ga)Se2-Based Solar Cells: Preprint},
author = {Contreras, M. and Barnes, T. and van de Lagemaat, J. and Rumbles, G. and Coutts, T. J. and Weeks, C. and Glatkowski, P. and Levitsky, I. and Peltola, J.},
abstractNote = {We present a new thin-film solar cell structure in which the traditional transparent conductive oxide electrode (ZnO) is replaced by a transparent conductive coating consisting of a network of bundled single-wall carbon nanotubes. Optical transmission properties of these coatings are presented in relation to their electrical properties (sheet resistance), along with preliminary solar cell results from devices made using CuIn1-xGaxSe2 thin-film absorber materials. Achieving an energy conversion efficiency of >12% and a quantum efficiency of {approx}80% demonstrate the feasibility of the concept. A discussion of the device structures will be presented considering the physical properties of the new electrodes comparing current-voltage results from the new solar cell structure and those from standard ZnO/CdS/Cu(In,Ga)Se2/Mo solar cells.},
doi = {10.1109/WCPEC.2006.279481},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2006},
month = {Mon May 01 00:00:00 EDT 2006}
}

Conference:
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  • We present a new thin-film solar cell structure in which the traditional transparent conductive oxide electrode (ZnO) is replaced by a transparent conductive coating consisting of a network of bundled single-wall carbon nanotubes. Optical transmission properties of these coatings are presented in relation to their electrical properties (sheet resistance), along with preliminary solar cell results from devices made using CuIn{sub 1-x}Ga{sub x}Se{sub 2} thin-film absorber materials. Achieving an energy conversion efficiency of >12% and a quantum efficiency of {approx}80% demonstrate the feasibility of the concept. A discussion of the device structures will be presented considering the physical properties of themore » new electrodes comparing current-voltage results from the new solar cell structure and those from standard ZnO/CdS/Cu(In,Ga)Se{sub 2}/Mo solar cells.« less
  • Thin films of single-wall carbon nanotubes were used as the transparent top electrical contact in Cu(In,Ga)Se{sub 2}- based solar cells. Specifically, we demonstrate that thin layers of carbon nanotubes in combination with insulating polymer layers can effectively replace the metal oxide layers typically used in polycrystalline thin-film solar cells. Replacing the standard n-type ZnO layer with a thin film of carbon nanotubes yielded energy conversion efficiencies up to 13%. The optical and electrical transport properties of the single-wall carbon nanotubes suggest that suitable applications for these materials include multiple-junction solar cells, thermophotovoltaics, and other applications benefiting from a p-type transparentmore » conductor with high near-infrared transmission.« less
  • We investigated the electronic properties of ZnO/CdS/CIGS /Mo/SLG polycrystalline thin-film solar cells with compositions ranging from Cu-rich to In(Ga)-rich by deep-level transient spectroscopy (DLTS) and capacitance-voltage (C-V) measurements. This compositional change represents the evolution of the film during growth by the 3-stage process. Two sets (four samples each) of CIGS thin films were prepared with Ga/(In+Ga) ratios of~0.3 (low Ga) and~0.6 (high Ga). The Cu/(In+Ga) ratio ranges from 1.24 (Cu-rich) to 0.88 (In(Ga)-rich). The films were treated with NaCN to remove the Cu2-xSe phase where needed. Key results include: (1) For low-Ga devices, DLTS data show that acceptor-like traps dominatemore » in samples where CIGS grains do not go through the Cu-rich to In(Ga)-rich transition, whereas donor-like traps dominate in In(Ga)-rich samples. Therefore, we see a clear transformation of defects from acceptor-like to donor-like traps. The activation energies of these traps range from 0.12 to 0.63 eV. We also observed that NaCN treatment eliminates a deep minority trap in the In(Ga)-rich devices, (2) For high-Ga devices, only majority-carrier traps were detected. These traps again range from shallow to deep, (3) The carrier concentration around the junction and the density of traps decrease as the CIGS becomes more In(Ga)-rich.« less
  • This report outlines improvements to the energy conversion efficiency in wide bandgap (Eg>1.2 eV) solar cells based on CuIn1-xGaxSe2. Using (a) alkaline containing high temperature glass substrates, (b) elevated substrate temperatures 600˚C-650˚C and (c) high vacuum evaporation from elemental sources following NREL's three-stage process, we have been able to improve the performance of wider bandgap solar cells with 1.218% for absorber bandgaps ~1.30 eV and efficiencies ~16% for bandgaps up to ~1.45 eV. In comparing J-V parameters in similar materials, we establish gains in the open-circuit voltage and, to a lesser degree, the fill factor value, as the reason formore » the improved performance. The higher voltages seen in these wide gap materials grown at high substrate temperatures may be due to reduced recombination at the grain boundary of such absorber films. Solar cell results, absorber materials characterization, and experimental details are reported.« less
  • We report on recent advances in the development of nanoscale measurements of the surface photovoltage (SPV) based on scanning tunneling microscopy (STM) and its application to the kesterites Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe). One critical aspect of the electronic structure of Cu(In,Ga)Se2 (CIGS) that has yet to be determined in their related kesterite compounds is the character of the surface electronics. In CIGS, spontaneous deviations in the stoichiometry of the surface cause a depletion (or even a type inversion) region that reinforces the CIGS homojunction. First-principle calculations predict that this inversion region will be more difficult to form in CZTS.more » In this contribution, the characteristics of the surface space charge region for both CIGS and CZTS(e) are investigated by STM. The implications of the results of these measurements on the future development of CZTS solar cells will be discussed.« less