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Title: Intense pulsed light annealing of copper zinc tin sulfide nanocrystal coatings

Abstract

A promising method for forming the absorber layer in copper zinc tin sulfide [Cu{sub 2}ZnSnS{sub 4} (CZTS)] thin film solar cells is thermal annealing of coatings cast from dispersions of CZTS nanocrystals. Intense pulsed light (IPL) annealing utilizing xenon flash lamps is a potential high-throughput, low-cost, roll-to-roll manufacturing compatible alternative to thermal annealing in conventional furnaces. The authors studied the effects of flash energy density (3.9–11.6 J/cm{sup 2}) and number of flashes (1–400) during IPL annealing on the microstructure of CZTS nanocrystal coatings cast on molybdenum-coated soda lime glass substrates (Mo-coated SLG). The annealed coatings exhibited cracks with two distinct linear crack densities, 0.01 and 0.2 μm{sup −1}, depending on the flash intensity and total number of flashes. Low density cracking (0.01 μm{sup −1}, ∼1 crack per 100 μm) is caused by decomposition of CZTS at the Mo-coating interface. Vapor decomposition products at the interface cause blisters as they escape the coating. Residual decomposition products within the blisters were imaged using confocal Raman spectroscopy. In support of this hypothesis, replacing the Mo-coated SLG substrate with quartz eliminated blistering and low-density cracking. High density cracking is caused by rapid thermal expansion and contraction of the coating constricted on the substrate as it is heated andmore » cooled during IPL annealing. Finite element modeling showed that CZTS coatings on low thermal diffusivity materials (i.e., SLG) underwent significant differential heating with respect to the substrate with rapid rises and falls of the coating temperature as the flash is turned on and off, possibly causing a build-up of tensile stress within the coating prompting cracking. Use of a high thermal diffusivity substrate, such as a molybdenum foil (Mo foil), reduces this differential heating and eliminates the high-density cracking. IPL annealing in presence of sulfur vapor prevented both low- and high-density cracking as well as blistering. However, grain growth was limited even after annealing with 400 flashes. This lack of grain growth is attributed to a difficulty of maintaining high sulfur vapor pressure and absence of alkali metal impurities when Mo foil substrates are used.« less

Authors:
; ; ; ; ;  [1]
  1. Department of Chemical Engineering and Materials Science, University of Minnesota, 151 Amundson Hall, 421 Washington Avenue SE, Minneapolis, Minnesota 55455 (United States)
Publication Date:
OSTI Identifier:
22592835
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films; Journal Volume: 34; Journal Issue: 5; Other Information: (c) 2016 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING; ANNEALING; BLISTERS; COATINGS; COPPER; CRACKING; DENSITY; FINITE ELEMENT METHOD; MOLYBDENUM; NANOSTRUCTURES; RAMAN SPECTROSCOPY; SOLAR CELLS; SUBSTRATES; SULFUR; THERMAL DIFFUSIVITY; TIN SULFIDES; VAPOR PRESSURE; XENON; ZINC SULFIDES; CDZNTE SEMICONDUCTOR DETECTORS

Citation Formats

Williams, Bryce A., Smeaton, Michelle A., Holgate, Collin S., Trejo, Nancy D., Francis, Lorraine F., E-mail: francis@umn.edu, and Aydil, Eray S., E-mail: aydil@umn.edu. Intense pulsed light annealing of copper zinc tin sulfide nanocrystal coatings. United States: N. p., 2016. Web. doi:10.1116/1.4961661.
Williams, Bryce A., Smeaton, Michelle A., Holgate, Collin S., Trejo, Nancy D., Francis, Lorraine F., E-mail: francis@umn.edu, & Aydil, Eray S., E-mail: aydil@umn.edu. Intense pulsed light annealing of copper zinc tin sulfide nanocrystal coatings. United States. doi:10.1116/1.4961661.
Williams, Bryce A., Smeaton, Michelle A., Holgate, Collin S., Trejo, Nancy D., Francis, Lorraine F., E-mail: francis@umn.edu, and Aydil, Eray S., E-mail: aydil@umn.edu. Thu . "Intense pulsed light annealing of copper zinc tin sulfide nanocrystal coatings". United States. doi:10.1116/1.4961661.
@article{osti_22592835,
title = {Intense pulsed light annealing of copper zinc tin sulfide nanocrystal coatings},
author = {Williams, Bryce A. and Smeaton, Michelle A. and Holgate, Collin S. and Trejo, Nancy D. and Francis, Lorraine F., E-mail: francis@umn.edu and Aydil, Eray S., E-mail: aydil@umn.edu},
abstractNote = {A promising method for forming the absorber layer in copper zinc tin sulfide [Cu{sub 2}ZnSnS{sub 4} (CZTS)] thin film solar cells is thermal annealing of coatings cast from dispersions of CZTS nanocrystals. Intense pulsed light (IPL) annealing utilizing xenon flash lamps is a potential high-throughput, low-cost, roll-to-roll manufacturing compatible alternative to thermal annealing in conventional furnaces. The authors studied the effects of flash energy density (3.9–11.6 J/cm{sup 2}) and number of flashes (1–400) during IPL annealing on the microstructure of CZTS nanocrystal coatings cast on molybdenum-coated soda lime glass substrates (Mo-coated SLG). The annealed coatings exhibited cracks with two distinct linear crack densities, 0.01 and 0.2 μm{sup −1}, depending on the flash intensity and total number of flashes. Low density cracking (0.01 μm{sup −1}, ∼1 crack per 100 μm) is caused by decomposition of CZTS at the Mo-coating interface. Vapor decomposition products at the interface cause blisters as they escape the coating. Residual decomposition products within the blisters were imaged using confocal Raman spectroscopy. In support of this hypothesis, replacing the Mo-coated SLG substrate with quartz eliminated blistering and low-density cracking. High density cracking is caused by rapid thermal expansion and contraction of the coating constricted on the substrate as it is heated and cooled during IPL annealing. Finite element modeling showed that CZTS coatings on low thermal diffusivity materials (i.e., SLG) underwent significant differential heating with respect to the substrate with rapid rises and falls of the coating temperature as the flash is turned on and off, possibly causing a build-up of tensile stress within the coating prompting cracking. Use of a high thermal diffusivity substrate, such as a molybdenum foil (Mo foil), reduces this differential heating and eliminates the high-density cracking. IPL annealing in presence of sulfur vapor prevented both low- and high-density cracking as well as blistering. However, grain growth was limited even after annealing with 400 flashes. This lack of grain growth is attributed to a difficulty of maintaining high sulfur vapor pressure and absence of alkali metal impurities when Mo foil substrates are used.},
doi = {10.1116/1.4961661},
journal = {Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films},
number = 5,
volume = 34,
place = {United States},
year = {Thu Sep 15 00:00:00 EDT 2016},
month = {Thu Sep 15 00:00:00 EDT 2016}
}