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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. 2016. "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 = 2016,
month = 9
}
  • In a line with most recent trends in developing non-toxic fluorescent nanomaterials, we combined blue emissive carbon dots with green and red emissive zinc copper indium sulfide (ZCIS) core/shell quantum dots (QDs) to achieve white light-emitting diodes (WLEDs) with a high color rendering index of 93. This indicates that ZCIS QDs, with their broad emission bands, can be employed to effectively make up the emission of carbon dots in the yellow and red regions to produce WLEDs in the wide region of color temperature by tuning the volume ratio of these constituting luminophores. Their electroluminescence characteristics including color rendering index,more » Commission Internationale de l'Eclairage (CIE) color coordinates, and color temperatures were evaluated as a function of forward current. The CIE-1931 chromaticity coordinates of the as-prepared WLEDs, exhibiting good stability, were slightly shifted from (0.321, 0.312) at 10 mA to (0.351, 0.322) at 30 mA, which was mainly caused by the different thermal quenching coefficients of carbon dots and ZCIS QDs.« less
  • Multilayer film stacks of ZnS and Cu{sub x}S (x ∼ 2) were made via atomic layer deposition. The precursors were bis(2,2,6,6-tetramethyl-3,5-heptanedionato)zinc, bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper, and H{sub 2}S generated in situ for sulfur. Samples were deposited at 200 °C, in layers ranging from approximately 2 to 20 nm thick, based on binary growth rates. The properties of the film stacks were studied with atomic force microscopy, ultraviolet–visible spectroscopy, and extended x-ray absorption fine structure. The results demonstrate that the structure of films with the thinnest layers is dominated by Cu{sub x}S, whereas in the thicker films, the structure is determined by whichever material is first deposited.more » This can be attributed to the crystal structure mismatch of ZnS and Cu{sub x}S.« less
  • The influence of thermal annealing on the photoluminescence, electroluminescence, and the transmission and reflection spectra in nanocrystalline zinc sulfide films has been studied. All the samples exhibit a broad emission band, the intensity of which depends on the annealing temperature. It is shown that luminophors, the crystal lattice of which includes imperfections that appeared in the transition from wurtzite to sphalerite, feature the highest emission intensity.
  • CuInSe{sub 2} crystals were sulfurized in a H{sub 2}S-Ar gas mixture at 575 deg. C. The focus was on the resulting mass transport, in particular, on the interdiffusion of Se and S. Experiments were done for various sulfurization times, and the resulting S distribution was measured by Auger electron spectroscopy sputter depth profiling and analyzed with the Boltzmann-Matano method. A one-dimensional diffusion process had shaped the S distribution in these crystals. The respective diffusion coefficient was on the order of 10{sup -16} cm{sup 2}/s, and it varied only slightly with the S content in CuIn(Se,S){sub 2}.