Figure 1.
CIGO nanoparticle characterization.
(A) TEM of FSP as-prepared CIGO nanoparticles. (B) XRD patterns for the CIGO sample prepared by FSP in part (A) and CIGS species obtained after its sulfurization.
Figure 2.
CIGO-PAH dispersion characterization.
(A) Particle size distribution and concentration for the fresh 1 mg CIGO-PAH⋅mL−1 (aq) dispersion determined using the NanoSight LM10-HSBF nanoparticle tracking system. (B) UV-visible absorbance spectrum of a freshly prepared 0.33 mg CIGO-PAH⋅mL−1 aqueous dispersion in a b = 0.10 cm pathlength cuvette vs. a water baseline. The peak at 285 nm corresponds to incompletely oxidized species within the particles.
Figure 3.
Aqueous CIGO dispersion stability.
Particle size dispersion histograms from DLS illustrating the time dependent aggregation of the quiescent 1-PAH⋅mL−1 (aq) dispersion are shown. (A) aged 3 days; (B) aged 3 days, after mixing; (C) aged 6 days, 10 min after mixing; (D) aged 6 days, 40 min after mixing; (E) aged 7 days, 10 min after mixing; (F) aged 13 days, 10 min after mixing. Particles larger than 300 nm were set as the aggregation threshold.
Figure 4.
Aqueous CIGO dispersion stability in pH 8.25 buffer.
Particle size histograms from DLS illustrating the time dependent aggregation of the 1-PAH⋅mL−1 20 mM Tris pH 8.25 (aq) dispersion are shown. (A) At preparation (t = 0 min). (B) t = 30 min after preparation. (C) t = 50 min after preparation. (D) t = 420 min after preparation. Insets in parts (C) and (D) are expansions of the particle distributions for particles larger than 400 nm diameter.
Figure 5.
Film fabrication scheme using CIGO-PAH colloids and PSS or PDA polyelectrolytes.
Process sequence (not to scale): (1) Treatment of substrate with PSS (aq) or pH 8.25 dopamine (aq) solution (for in situ PDA generation) followed by CIGO-PAH (aq) dispersion or CIGO-PAH/Tris pH 8.25 (aq) dispersion to deposit first bilayer of PSS/CIGO-PAH or PDA/CIGO-PAH, respectively. Repetition of treatment cycle deposits additional bilayers for multilayer film fabrication; (2) Air oxidation for 5 h at 550°C to remove organic components from CIGO particles; (3) Sulfurization for 3 h at 550°C in H2S to convert CIGO particles to CIGS film. Consult the Experimental Section and text for additional details.
Figure 6.
Characterization of PSS/CIGO-PAH multilayers prepared by hand dipcoating.
(A) Absorbance spectra in descending order at 285 nm of PSS/CIGO-PAH multilayer films of structure Q-EDA/(PSS/PAH)3/(PSS/CIGO-PAH)x with x = 18 (black, solid), x = 18 after annealing in air 5 h at 550°C (blue, dashed), x = 12 (red, solid), and x = 6 (green, solid). Note that the measured absorbance represents films having the structures shown that are present on both sides of the quartz slide. (B) Absorbance vs. number of bilayers, x, for Q-EDA/(PSS/PAH)3/(PSS/CIGOPAH)x multilayers. Red squares (225 nm) and black circles (285 nm) indicate a film initiated using 2 day aged CIGO-PAH; Blue diamonds (225 nm) and green triangles (285 nm) indicate a film initiated using fresh CIGO-PAH.
Figure 7.
Characterization of PSS/CIGO-PAH multilayers prepared by robot dipcoating.
(A) Absorbance vs. number of bilayers, x, for Q-EDA/(PSS/CIGO-PAH)x multilayers prepared via automated dipcoating using the robot. (B) Absorbance spectra in ascending order at 400 nm of robot dipcoated PSS/CIGO-PAH multilayer films of structure Q-EDA/(PSS/CIGO-PAH)80 after annealing in air 5 h at 550°C (blue), as deposited (black), and after H2S sulfurization 5 h at 550°C (red). Note that the measured absorbance derives from films having the structures shown that are present on both sides of the quartz slide.
Figure 8.
Deposition of polydopamine thin films.
(A) Absorbance spectrum of polydopamine (PDA) film on a Q-EDA slide prepared by 90 min treatment in freshly made 1 mg dopamine⋅mL−1 10 mM Tris pH 8.25 (aq) solution. Spectrum shown after subtraction of an untreated Q-EDA slide baseline. Note that the measured absorbance represents PDA films that are present on both sides of the quartz slide. (B) Time dependent absorbance at 285 nm for Q-EDA slide treated with 1 mg dopamine⋅mL−1 10 mM Tris pH 8.25 (aq) buffer solution.
Figure 9.
Characterization of PDA/CIGO-PAH multilayers prepared by hand dipcoating.
(A) Absorbance vs. number of bilayers, x, for Q-EDA/(PDA/CIGO-PAH)x multilayers deposited by hand dipcoating. (B) Absorbance spectra in ascending order at 600 nm of hand dipcoated PDA/CIGO-PAH multilayer films of structure Q-EDA/(PDA/CIGO-PAH)20 after annealing in air 5 h at 550°C (blue) with thickness 953±162 nm, as deposited (black) with thickness 1163±189 nm, and after sulfurization 5 h at 550°C (red) with thickness 1079±168 nm. Film thicknesses were measured by profilometry. Note that the measured absorbance derives from films having the structures shown that are present on both sides of the quartz slide.
Figure 10.
SEM images of Si-EDA/(PDA/CIGO-PAH)26/PDA films.
Top-views (A, C, E) and side-views (B, D, F, G) for as-deposited film (A, B), as-deposited film after 5 h air oxidation at 550°C (C, D), and oxidized film after sulfurization 3 h in H2S at 550°C (E, F, G) are shown.
Figure 11.
XRD of the CIGS film shown in Figures 9E–G.
Consult the text for additional details and discussion.