Anisotropic Optoelectronic Properties of

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1 1 Supporting Information Anisotropic Optoelectronic Properties of Melt-Grown Bulk CsPbBr 3 Single Crystal Peng Zhang, Guodong Zhang*, Lin Liu, Dianxing Ju, Longzhen Zhang, Kui Cheng, Xutang Tao* 1. Synthesis and purification of CsPbBr3 polycrystals High-purity CsBr (5N, g) and PbBr2 (5N, g) with a stoichiometric ratio were sealed in a quartz tube in vacuation. Polycrystalline CsPbBr3 was successfully synthesized at 600 ºC for 24 h in a temperature controlled well furnace. Then the polycrystalline CsPbBr3 was refined by repeated directional crystallization with prior removal of dirty to obtain the high-pure CsPbBr3. The obtained orange product was identified as pure phase CsPbBr3 by powder XRD measurement as shown in Figure S1. Figure S1. The power XRD pattern of the polycrystalline CsPbBr3.

2 2 2. CsPbBr3 single crystal growth and orientation 170 g polycrystalline CsPbBr3 were sealed into a quartz ampoule (24 mm ID). Then the ampoule was moved to the 2-zone Bridgman furnace for single crystal growth. The high temperature zone is 600 C and low temperature zone is 200 C. The temperature gradient of the furnace was about C/cm. After heating at the high temperature zone for 12 h, the ampoule dropped slowly with a speed of 1 mm/h. Finally, the furnace temperature cooled down to room temperature through 3 days, an ultra-large crack-free CsPbBr3 single crystal was obtained. The crystal was oriented by the X-ray Laue back diffraction technique, and the diffraction patterns of (100), (010), and (001) plane were shown in Figure S2. The welldefined reflections confirm the orientation and the high quality of the three planes. Figure S2. (a), (b) and (c) is the X-ray Laue back diffraction patterns of (100), (010), and (001) plane, respectively. 3. Calculation of the mobility measured by the SCLC method In all of the current-voltage (I V n ) curves, the Ohmic (n = 1), trap-filling (n > 3) and Child (n = 2) regions were observed with the increase of bias voltages. When operating in the trap-free space charge limit current (SCLC) regime (n=2), the dark current was well fitted (Figure 3, yellow line) by the Mott-Gurney law: J D = 9εε 0μV 2 8L 3, where JD is the current density, ε is the relative dielectric constant, ɛ0 is vacuum permittivity, μ is the charge mobility, V is the applied voltage and L is the thickness of

3 3 the sample. Then it is easy to obtain the equation: μ = 8J DL 3 2. By transforming the 9εε 0 V equation μ = 8J DL 3 9εε 0 V 2 to lg μ = lg 8J DL 3 2 lg V, which exhibit a linear relationship, 9εε 0 the value of the mobility (μ) can be calculated when the value of 2 lg V is zero. A simple way is to take the value of the intercept of Child region on the Y axis for the current (I), then the JD can be calculated by the equation: J D = I s, where s is the area of the electrode. Taking a direction of sample 1 as an example, I = A, s = 18 mm 2, L = 1.1 mm, ɛ = 22.9, ɛ0 is the vacuum permittivity ( F/m). So, it is easy to calculate the mobility value of 3.54 cm 2 /Vs for a direction of sample The simulated pattern of the gold interdigital electrode In the photoresponse measurement, gold interdigital electrode was integrated to collect the current, with each electrode consisting of a group of 5 fine Au wires (2 mm in length, and 0.25 mm in width). The simulated pattern of the gold interdigital electrode was shown in Figure S3. The effective illuminated area was calculated to 8.25 mm 2. Figure S3. The simulated pattern of the gold interdigital electrode 5. The light excitation measurements from 365 nm to 555 nm The light excitation measurements were applied by a xenon lamp with a fixed light

4 4 power density of 30 μw. The measurement results were shown in Figure S4, and the optimal excitation wavelength was determined about 532 nm for all three devices. Figure S4. (a), (b) and (c) is the light excitation measurement by a xenon lamp from 365 nm to 555 nm for (100), (010), and (001) plane, respectively. Figure S5. (a), (b) and (c) is the irradiation light power density dependence of the R and EQE under 10V bias for (100), (010), and (001), respectively. (d), (e) and (f) is the irradiation light power density dependence of the D* under 10V bias for (100), (010), and (001), respectively. 6. Detail of the measurements X-ray powder diffraction (XRD) patterns of polycrystalline CsPbBr 3 powder and crystal planes were carried out on a Bruker-AXS D8 Advance X-ray diffractometer. X- ray Laue back diffraction of the crystal planes were performed by a Laue diffractometer (MWL 120, MULTIWIRE LABORATORIES, Ltd). Ultraviolet-visible absorption spectrum was measured using a conventional UV/Vis spectrometer (Hitachi U-4100) equipped with an integrating sphere over the spectral range nm.

5 5 Photoluminescence spectrum measurements was carried out by the 410 nm excitation light from a monochromator with Xenon lamp (50 W) as light source was focused on the sample through an optical chopper (SRS 540). Time-resolved photoluminescence spectra measurement was performed on a FLS920 Combined Fluorescence Lifetime and Steady State Spectrometer (Edinburgh, U.K.). The Ultraviolet photoelectron spectroscopy were measurement by the Kratos Axis Ultra DLD. SCLC measurements were carried out by Keithley 4200 semiconductor parameter analyzer. The CsPbBr3 crystal planes with the thickness of about 1.1 mm and all of them were deposited with Ti conduction film as the electrodes. Photoresponse measurement for the photodetector were collected by a Keithley 4200 with a source meter of a 532 nm wavelength laser. All above measurements were carried out at room temperature.