Structural and Photophysical Properties of Methylammonium Lead Tribromide (MAPbBr3) Single Crystals

Abstract

The structural and photophysical characteristics of MAPbBr₃ single crystals prepared using the inverse temperature crystallization method are evaluated using temperature-dependent X-ray diffraction (XRD) and optical spectroscopy. Contrary to previous research reports on perovskite materials, we study phase transitions in crystal lattice structures accompanied with changes in optical properties expand throughout a wide temperature range of 300-1.5 K. The XRD studies reveal several phase transitions occurred at ~210 K, ~145 K, and ~80 K, respectively. The coexistence of two different crystallographic phases was observed at a temperature below 145 K. The emission peaks in the PL spectra are all asymmetric in line shape with weak and broad shoulders near the absorption edges, which are attributed to the Br atom vacancy on the surface of the crystals. The time-resolved PL measurements reveal the effect of the desorption/adsorption of gas molecules on the crystal surface on the PL lifetimes. Raman spectroscopy results indicate the strong interplays between cations and different halide atoms. Lastly, no diamagnetic shift or split in emission peaks can be observed in the magneto-PL spectra even at an applied magnetic field up to 5 T and at a temperature as low as 1.5 K.

Figure 1

(a) Powder and (b) single-crystal XRD patterns of MAPbBr₃ single crystal at 300 K. The inset displays an optical image of the single crystal grown by the ITC method.

Figure 2

(a) UV-Vis absorption and PL spectra of the solution grown MAPbBr₃ single crystal excited at 405 nm at room temperature (b) fitting of the PL spectrum by peaks 1 and 2. X_c1, X_c2, W₁, W₂, I₁, and I₂ represent the peak positions, bandwidths at FWHM, and normalized intensity of peaks 1 and 2, respectively. Inset shows the onset of the absorption at ~2.21 eV.

Figure 3

Transient PL curves recorded (a) under ambient conditions and (b) in a vacuum at an excitation wavelength of 405 nm at room temperature. The respose time of the system is ~1 ns.

Figure 4

(a) Photo image of the as-synthesized MAPbCl₃ single crystal and Raman spectra of MAPbBr₃ and MAPbCl₃ single crystals cover from (b) 200–400 cm⁻¹ (c) 800–2000 cm⁻¹ and (c) 2000–4000 cm⁻¹.

Figure 5

Single-crystal XRD spectra of the (100) and (200) peaks of MAPbBr₃ single crystals at 260–180 K.

Figure 6

(a) PL spectra of MAPbBr₃ single crystal excited at 405 nm at 295–170 K (b) fitting of the representative PL spectrum by peaks 1 and 2. X_c1, X_c2, W₁, W₂, I₁, and I₂ represent the peak positions, bandwidths at FWHM, and normalized intensity of peaks 1 and 2, respectively. (c,d,e) Temperature-dependent peak positions, bandwidths and intensity of peaks 1 and 2 at 295–170 K.

Figure 7

UV-Vis absorption and PL spectra of MAPbBr₃ single crystals excited at 405 nm at (a) 230 K and (b) 180 K. The insets show the fitting of the absorption onset.

Figure 8

Single-crystal XRD spectra of (100) and (200) peaks of MAPbBr₃ single crystals at 160–120 K.

Figure 9

(a) PL spectra of MAPbBr₃ single crystals excited at 405 nm at 170–110 K (b) fitting of the representative PL spectrum by peaks 1 and 2. X_c1, X_c2, W₁, W₂, I₁, and I₂ represent the peak positions, bandwidths at FWHM, and normalized intensity of peaks 1 and 2, respectively. (c,d,e) Temperature-dependent peak positions, bandwidths and intensity of peaks 1 and 2 at 170–110 K.

Figure 10

Single-crystal XRD spectra of (100) and (200) peaks of MAPbBr₃ single crystal at 140–20 K.

Figure 11

(a) PL spectra of MAPbBr₃ single crystals excited at 405 nm at 110–30 K (b) fitting of the representative PL spectrum by peaks 1, 2, 3, and 4. X_c1, X_c2, X_c3, W₁, W₂, W₃, I₁, I₂, and I₃ are the peak positions, bandwidths, and intensity of peaks 1, 2, and 3, respectively. (c,d,e) Temperature-dependent peak positions, bandwidths, and intensity of peaks 1, 2, and 3 at 110–30 K. The inset in (b) shows the fitting of the absorption onset at 30 K.

Figure 12

UV-Vis absorption and PL spectra of MAPbBr₃ single crystals excited at 405 nm at 80 K. Inset shows the fitting of the absorption onset at ~2.25 eV.

Figure 13

Magneto-PL spectra as a function of the magnetic field in Faraday geometry with the field applied (a) parallel and (b) perpendicular to the (100) direction at 1.5 K and scanned magnetic field up to 5 T.