Screening in crystalline liquids protects energetic carriers in hybrid perovskites by Haiming Zhu, Kiyoshi Miyata, Yongping Fu, Jue Wang, Prakriti P. Joshi, Daniel Niesner, Kristopher W. Williams, Song Jin, and X.-Y. Zhu Science Volume 353(6306):1409-1413 September 23, 2016 Published by AAAS

Fig. 1 Time-dependent PL spectra revealing long-lived hot carriers. 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. Haiming Zhu et al. Science 2016;353:1409-1413 Published by AAAS

Fig. 2 Time-dependent PL spectra from FAPbBr3 and CsPbBr3 showing hot PL emission only from the former. 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. Haiming Zhu et al. Science 2016;353:1409-1413 Published by AAAS

Fig. 3 Time-resolved optical Kerr effect (TR-OKE) transients. 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. Haiming Zhu et al. Science 2016;353:1409-1413 Published by AAAS

Fig. 4 Time-dependent PL spectra from MAPbBr3 at two temperatures, showing hot PL emission at 180 K but not at 77 K. 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. Haiming Zhu et al. Science 2016;353:1409-1413 Published by AAAS