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Aggregation-induced emission in lamellar solids of colloidal perovskite quantum wells

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Science Advances  22 Dec 2017:
Vol. 3, no. 12, eaaq0208
DOI: 10.1126/sciadv.aaq0208
  • Fig. 1 Crystal structure and surface characterization of lamellar solids containing layer-controlled CQWs.

    (A) Schematics of the superlattice structure in lamellar solids showing layer-controlled perovskite CQWs (n = 3 here) sandwiched between long alkyl ligands. AFM height (B) and phase (C) images of n = 3 MA lamellar solid deposited on glass substrate. Scale bars, 1 μm. deg, degree. Synchrotron GISAXS (D) and GIWAXS (E) patterns for the same sample, with the superlattice signals labeled. (F) GIWAXS pattern of n = 3 MA drop-casted film showing the extended DS rings along the angular coordinate χ. (G) Comparison of orientation distribution function using the normalized scattering intensity of the (002) DS ring with respect to χ in lamellar and drop-casted solids.

  • Fig. 2 Comparison of photophysical properties between CQW solution and solids.

    (A) Photographs under UV excitation (top) and emission spectra under 370-nm excitation (bottom) for MA lamellar solids with different n values. (B) Absolute ηPL as a function of n in solution, lamellar solid, and drop-casted film of MA samples. (C) Absolute ηPL and emission wavelength (λPL) as a function of CQW concentration. (D) TRPL of n = 3 MA samples under a low pumping energy P, highlighting an inverse correlation between τe and ηPL. (E) Extracted monoexponential lifetime as a function of initial carrier density in n = 3 MA samples, showing weak dependence on initial carrier concentration n0.

  • Fig. 3 Multiscale analysis of n = 3 MA CQWs in solution and lamellar solid.

    (A) Computer-generated molecular models (brown, carbon; light pink, hydrogen; green, bromine; light blue, nitrogen; gray, lead; violet, carbon in toluene) of individual CQW in toluene (top) and in aggregated CQWs (lamellar solid; bottom) with n = 3 MA compound. (B) Three-dimensional schematics of the orientation of each organic cation (blue arrow corresponding to the N-C axis) defined by a spherical coordinate system with polar axis along the z direction, as well as in-plane azimuthal (φ) and polar (θ) angles. Orientational distribution contour maps (φ, θ) of surface MA cations in (C) toluene solution and (D) lamellar solid. (E) Brillouin zone of bulk (faint blue) and N-layer (faint orange) perovskite QW lattice in an orthorhombic cell. Symmetry points at boundaries of the zone where the bandgap is direct change from R (in bulk) to M (in N-layers). kz is oriented perpendicular to the QW surface. (F) Calculated band structures of n = 3 MA QWs with different orientations of surface MA cations, along [111], [010], [011], and [100] directions. The most indirect bandgap is observed for the [011] with a wave vector difference Δky relative to the M point. The most direct bandgap is observed for the [100] with no relative displacement along ky. (G) Magnification of the bands around the M point for small kx and ky, highlighting the change in the band edges for the different MA configurations. Top and bottom panels show the conduction and valence bands, respectively, highlighted with filled points. Labels follow those in (F).

  • Fig. 4 Demonstration of the ultrapure green emission through DC using n = 7 MA CQW solid.

    (A) Schematic setup (left) and photographs (right) for the LED device that yields pure green emission pumped by blue GaN LED chips (456 nm). (B) Electroluminescence (EL) spectra before (black) and after CQW solid DC (orange). Emission spectra for a commercial green InGaN LED (blue) are also attached for comparison. (C) Calculated luminous efficacy as a function of luminance for the two green LEDs considered.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/12/eaaq0208/DC1

    text S1. Blue DC LEDs.

    text S2. ASE experiments.

    fig. S1. Photoluminescence properties of perovskite CQWs in solution.

    fig. S2. Optical absorption of perovskite CQW samples.

    fig. S3. Photoluminescence properties of FAPbBr3 CQWs.

    fig. S4. TRPL analysis of MAPbBr3 perovskite CQWs.

    fig. S5. Synchrotron GIWAXS pattern of lamellar solid composed of n = 1 MAPbBr3 CQWs.

    fig. S6. Morphology analysis of perovskite CQWs by means of STEM.

    fig. S7. SEM analysis of the film morphology.

    fig. S8. The orientation distribution map of bulk MA cations in n = 3 CQW.

    fig. S9. Surface MA cation orientation with 75% ligand coverage.

    fig. S10. Electronic band structures projected on states of Pb atoms (left column), Br atoms (middle column), and CH3NH3 molecules (right column).

    fig. S11. Charge density difference plots with different configurations.

    fig. S12. Final geometries after relaxation.

    fig. S13. CIE chromaticity coordinates of green (n = 7 to 10) and blue (n = 3) CQW solid phosphor-based DC-LEDs.

    fig. S14. Driving current (I) and luminance (L) as a function of voltage (V).

    fig. S15. Luminous efficacy as a function of luminance for commercial blue GaN LED as pumping source.

    fig. S16. Demonstration of blue DC emission using n = 3 MA CQW solid.

    fig. S17. Operational stability of n = 7 to 10 MA CQW downconverting film.

    fig. S18. Observation of ASE.

    fig. S19. The threshold behavior for the intensity of the ASE band.

    table S1. Ligand volumes.

    table S2. Absolute ηPL summary.

    movie S1. Ab initio MD of the n = 1 geometry viewed along the 001 axis.

    movie S2. Ab initio MD of the n = 1 geometry viewed along the 100 axis.

    movie S3. Ab initio MD of the n = 1 geometry viewed along the 010 axis.

    References (6568)

  • Supplementary Materials

    This PDF file includes:

    • text S1. Blue DC LEDs.
    • text S2. ASE experiments.
    • fig. S1. Photoluminescence properties of perovskite CQWs in solution.
    • fig. S2. Optical absorption of perovskite CQW samples.
    • fig. S3. Photoluminescence properties of FAPbBr3 CQWs.
    • fig. S4. TRPL analysis of MAPbBr3 perovskite CQWs.
    • fig. S5. Synchrotron GIWAXS pattern of lamellar solid composed of n = 1 MAPbBr3 CQWs.
    • fig. S6. Morphology analysis of perovskite CQWs by means of STEM.
    • fig. S7. SEM analysis of the film morphology.
    • fig. S8. The orientation distribution map of bulk MA cations in n = 3 CQW.
    • fig. S9. Surface MA cation orientation with 75% ligand coverage.
    • fig. S10. Electronic band structures projected on states of Pb atoms (left column), Br atoms (middle column), and CH3NH3 molecules (right column).
    • fig. S11. Charge density difference plots with different configurations.
    • fig. S12. Final geometries after relaxation.
    • fig. S13. CIE chromaticity coordinates of green (n = 7 to 10) and blue (n = 3) CQW solid phosphor-based DC-LEDs.
    • fig. S14. Driving current (I) and luminance (L) as a function of voltage (V).
    • fig. S15. Luminous efficacy as a function of luminance for commercial blue GaN LED as pumping source.
    • fig. S16. Demonstration of blue DC emission using n = 3 MA CQW solid.
    • fig. S17. Operational stability of n = 7 to 10 MA CQW downconverting film.
    • fig. S18. Observation of ASE.
    • fig. S19. The threshold behavior for the intensity of the ASE band.
    • table S1. Ligand volumes.
    • table S2. Absolute ηPL summary.
    • Legends for movies S1 to S3
    • References (65–68)

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    Other Supplementary Material for this manuscript includes the following:

    • movie S1 (.mp4 format). Ab initio MD of the n = 1 geometry viewed along the 001 axis.
    • movie S2 (.mp4 format). Ab initio MD of the n = 1 geometry viewed along the 100 axis.
    • movie S3 (.mp4 format). Ab initio MD of the n = 1 geometry viewed along the 010 axis.

    Files in this Data Supplement:

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