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Screening in crystalline liquids protects energetic carriers in hybrid perovskites

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Science  23 Sep 2016:
Vol. 353, Issue 6306, pp. 1409-1413
DOI: 10.1126/science.aaf9570
  • Fig. 1 Time-dependent PL spectra revealing long-lived hot carriers.

    (A) SEM image and selected area electron diffraction pattern (inset) of a single-crystal MAPbBr3 microplate. Scale bar: 10 μm. (B) Pseudocolor (intensity) plot of TR-PL spectra from a single-crystal MAPbBr3 microplate at room temperature under 3.08-eV excitation and an excitation density of 1.7 μJ cm−2. (C) PL intensity decay kinetics at 2.3 eV (red) and 2.6 eV (blue) and single exponential fits (solid). The PL intensity at 2.6 eV has been multiplied by a factor of 1500. (D) PL spectra (squares) at indicated delay times and fits (colored curves) to the two-temperature model. The black solid and dashed curves show components in the fit to the spectrum at 50 ps. (E) Extracted electronic temperature from the hot-carrier distribution as a function of delay time. The data points are average values from three independent microplate samples. The red curve is a single exponential fit to the first 0.5 ns, which gives a hot-carrier relaxation time constant of 150 ± 30 ps.

  • Fig. 2 Time-dependent PL spectra from FAPbBr3 and CsPbBr3 showing hot PL emission only from the former.

    (A and B) Pseudocolor plot of TR-PL spectra for a single-crystal FAPbBr3 microplate (A) and a single-crystal CsPbBr3 microplate (B). The excitation photon energy is 3.08 eV, and the excitation density is 1.7 μJ cm−2. (C and D) PL spectra at indicated delay times for FAPbBr3 microplate (C) and CsPbBr3 microplate (D). The experimental conditions are identical to those for MAPbBr3 in Fig. 1.

  • Fig. 3 Time-resolved optical Kerr effect (TR-OKE) transients.

    (A to C) The transients reveal liquid-like reorientational dynamics in (B) MAPbBr3 or (C) FAPbBr3, but not in (A) CsPbBr3. The pump-probe cross correlation (CC) is depicted with gray (70 fs full width at half maximum). The red curve in (A) is an exponential fit (convoluted with the pump-probe CC), which gives a decay time constant of 140 ± 10 fs. The labels of different components (1 to 4) are detailed in the text.

  • Fig. 4 Time-dependent PL spectra from MAPbBr3 at two temperatures, showing hot PL emission at 180 K but not at 77 K.

    (A and B) Pseudocolor plot of TR-PL spectra for a single MAPbBr3 microplate at 180 K (A) and at 77 K (B) under 3.08-eV excitation at an excitation density of 1.7 μJ cm−2. (C and D) PL spectra at indicated delay times for MAPbBr3 microplate at 180K (C) and at 77 K (D). See Fig. 1 for spectra from the same sample at 293 K.

Supplementary Materials

  • Screening in crystalline liquids protects energetic carriers in hybrid perovskites

    Haiming Zhu, Kiyoshi Miyata, Yongping Fu, Jue Wang, Prakriti P. Joshi, Daniel Niesner, Kristopher W. Williams, Song Jin, X.-Y. Zhu

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Supplementary Text
    • Figs. S1 to S12
    • Table S1
    • References