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Spin-dependent charge transport through 2D chiral hybrid lead-iodide perovskites

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Science Advances  06 Dec 2019:
Vol. 5, no. 12, eaay0571
DOI: 10.1126/sciadv.aay0571
  • Fig. 1 Structure and crystallographic orientation characterization.

    (A) Crystalline structure (30) of chiral perovskite, (R/S-)methylbenzylammonium lead iodide (R/S-MBA)2PbI4. (B to D) Crystallographic orientation characterization of perovskite thin films: 1D (B) and 2D XRD patterns (C and D). Note that layers are highly oriented as only (0 0 2l) peaks are observed. Intense Bragg spots further indicate the layers oriented parallel to the substrates. Inset: Crystallographic orientation of perovskite layers. a.u., arbitrary units.

  • Fig. 2 Morphological and photophysical characterization.

    (A to D) AFM images of (R-MBA)2PbI4 (A) and (S-MBA)2PbI4 (C), respectively. Inset: AFM height profile of the red line drawn in the AFM image. (B) Linear absorption (quartz substrate) and (D) circular dichroism (CD) spectra (quartz substrate). CD spectra display derivative features at 200 to 600 nm, with (R-MBA)2PbI4 and (S-MBA)2PbI4 showing opposite signs.

  • Fig. 3 mCP-AFM measurements.

    Schematic illustration of magnetic conductive-probe AFM (mCP-AFM) measurements (A) and chirality dependence in out-of-plane charge transport (B to D). Room-temperature I-V curves obtained using the mCP-AFM technique of chiral 2D hybrid perovskite thin films (~50 nm thick) for (R-MBA)2PbI4 (B), (S-MBA)2PbI4 (D), and nonchiral perovskite film PEA2PbI4 (C). The tip is magnetized in the north (blue), south (red), and nonmagnetized (black). The I-V response for each 2D film was averaged over 100 scans, and the shaded region around the lines marks the 95% confidence limits for the average results.

  • Fig. 4 MR response of spintronic devices based on chiral perovskites and schematic illustration of the device structure.

    MR(B) response of spintronic devices based on (R-MBA)2PbI4 (A), (S-MBA)2PbI4 (B), and (PEA)2PbI4 (C). The out-of-plane magnetic field was swept from −200 and 200 mT and back. The resistance was measured at an applied forward voltage of 0.5 V and a temperature of 10 K. The interlayer perovskite film thickness was ~60 nm for all devices.

  • Fig. 5 Thickness-dependent MR study and schematic diagram of the spin transport through the 2D chiral perovskite layers.

    The MRmax(d) response is decomposed into two components in spintronic devices based on (S-MBA)2PbI4 with different thicknesses (A). The black squares are experimental MRmax(d), whereas the red circles are simulation of spin relaxation process (exponential decay with thickness, assuming a spin diffusion length of ~40 nm) (39). The difference between the black squares and red circles are represented by the blue triangles, which is a rough estimation of the spin selectivity dependence with the thickness. These two competing effects are illustrated in (B). Spin selectivity occurs through each chiral layer, whereas spin relaxation happens mainly through each inorganic layer that has strong SOC.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/12/eaay0571/DC1

    Fig. S1. 2D XRD patterns for different 2D perovskite thin films.

    Fig. S2. AFM images of different 2D perovskite thin films.

    Fig. S3. Estimation of exciton splitting energy.

    Fig. S4. Raw and averaged I-V curves from the mCP-AFM measurements.

    Fig. S5. Thickness dependence of mCP-AFM studies.

    Fig. S6. Schematic energy diagram of the “half spin valve” device based on the chiral 2D perovskite thin films.

    Fig. S7. Voltage-dependent MR studies based on chiral (R-MBA)2PbI4 and (S-MBA)2PbI4 thin films.

    Reference (40)

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. 2D XRD patterns for different 2D perovskite thin films.
    • Fig. S2. AFM images of different 2D perovskite thin films.
    • Fig. S3. Estimation of exciton splitting energy.
    • Fig. S4. Raw and averaged I-V curves from the mCP-AFM measurements.
    • Fig. S5. Thickness dependence of mCP-AFM studies.
    • Fig. S6. Schematic energy diagram of the “half spin valve” device based on the chiral 2D perovskite thin films.
    • Fig. S7. Voltage-dependent MR studies based on chiral (R-MBA)2PbI4 and (S-MBA)2PbI4 thin films.
    • Reference (40)

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