Cs 2 PbI 2 Cl 2, All-Inorganic Two-Dimensional Ruddlesden-Popper Mixed Halide Perovskite with Optoelectronic Response

Transcription

1 Supporting Information Cs 2 PbI 2 Cl 2, All-Inorganic Two-Dimensional Ruddlesden-Popper Mixed Halide Perovskite with Optoelectronic Response Jiangwei Li,,, Qin Yu,, Yihui He, Constantinos C. Stoumpos, Guangda Niu, Giancarlo G. Trimarchi, Hang Guo, Guifang Dong, Dong Wang, *, Liduo Wang, and Mercouri G. Kanatzidis *, Department of Chemistry, Tsinghua University, Beijing , China Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information Huazhong University of Science and Technology, Wuhan , China S1

2 Table of Contents Experimental Details Synthesis and crystal growth Characterizations Theoretical Calculation methods Solid State Synthesis Figure S1 (Schematic view of 2D all-inorganic perovskite structures) Figure S2 (Powder XRD patterns of the solid state synthesis products) Figure S3 (Powder XRD and UV-Vis absorption of Cs 2 PbI 2 Cl 2 samples) Figure S4 (2-cycle DTA measurements of Cs 2 PbI 2 Cl 2 ) Figure S5 (Powder XRD and UV-Vis absorption before and after DTA) Figure S6 (PL properties of Cs 2 PbI 2 Cl 2 single crystals) Crystallographic Data of Cs 2 PbI 2 Cl 2 Table S1 (Crystal data and structure refinement) Table S2 (Atomic coordinates and equivalent isotropic displacement parameters) Table S3 (Anisotropic displacement parameters) Table S4 (Selective bond lengths and bond angles) Details of Theoretical Calculations Table S5 (Calculated E Total of all phases) Table S6 (Summary of Calculated H d ) Table S7 (Comparison of calculated unit cell parameters from different models) Table S8 (Calculated structural parameters of 2D perovskites) Table S9 (Calculated m e * and m h * in different direction) Figure S7 (PDOS analysis of Cs 2 PbI 2 Cl 2 and Cs 2 PbCl 2 I 2 ) Supplementary Data of Electrical Resistivity, Photo- and α-particle-response Measurements Figure S8 (Powder XRD pattern of the cleavage facets of Cs 2 PbI 2 Cl 2 single crystals) Figure S9 (Emission spectrum of the UV light source) Figure S10 (On-off cycling tests under UV light at low frequencies) Figure S11 (Response time analysis) Figure S12 (Supplementary α-particle-response results) Composition variations (Cs 2 SnI 2 Cl 2 and Rb-substituted case) Table S10 (Crystal structure comparison between Cs 2 PbI 2 Cl 2 and Cs 2 SnI 2 Cl 2 ) Figure S13 (Powder XRD of Rb 2 PbI 2 Cl 2 sample) Reference S2

3 Experimental Details Materials. PbCl 2 (99.999%), PbBr 2 (99.99%), PbI 2 (99.999%), CsCl (99.999%) CsBr (99.9%) and CsI (99.999%) were purchased from Sigma-Aldrich Inc. and used as received. Synthesis and Crystal Growth. The synthesis of Cs 2 PbI 2 Cl 2 polycrystalline raw material was performed with a solid state method. Stoichiometric mixtures of 2CsI (519.6 mg, 2 mmol) and PbCl 2 (278.1 mg, 1 mmol) or 2CsCl (336.8 mg, 2 mmol) and PbI 2 (461.0 mg, 1 mmol) were loaded in a 9 mm Pyrex tube (~15 cm) in a N 2 glovebox. The tube was then evacuated to 10-3 mbar and flame-sealed with liquid N 2 protection. The sealed tube was subsequently transferred to a tube furnace, heated to 500 ºC at a speed of 80 ºC/h, maintained at 500 ºC for 24 h, and then cooled down to room temperature over a period of 24 h. The completion of reaction gave an apparently pale white ingot with black impurity for most of the times. Crystals suitable for X-ray diffraction were picked up under microscope with a transparent plate-like shape. Large single crystals of Cs 2 PbI 2 Cl 2 were prepared from stoichiometric melt of 2CsCl (3.368 g) and PbI 2 (4.610 g) by the vertical Bridgman method. The temperature was set to be 500 C for the hot zone and 350 C for the cold zone. Before the growth process, the ampule was held in the hot zone for 24 h for complete melting. The ampule was then translated from the hot zone to the cold zone at a speed of 0.7 mm/h. Since Cs 2 PbI 2 Cl 2 is a fragile layered compound, a slow cooling process is preferred to alleviate the cracks of ingots induced by thermal stress. Normally, there are black CsPbI 3 secondary phases separated outside the ingots, leaving the transparent Cs 2 PbI 2 Cl 2 single crystals inside. Thinner single-crystalline flakes could further be obtained by mechanically cleaving. Single-Crystal X-ray Diffraction. Frames were collected using a STOE IPDS 2 diffractometer with graphite-monochromatized Mo Kα radiation (λ = Å), operating at 50 kv and 40 ma under N 2 flow. Integration and numerical absorption corrections were performed using the STOE X-AREA program suite. All structures were solved by direct methods and refined by full-matrix least-squares on F 2 using the OLEX2 package. Powder X-ray Diffraction. Powder XRD analysis was performed using a Rigaku Miniflex600 powder X-ray diffractometer (Cu Kα graphite, λ = Å) operating at 40 kv/15 ma with a Kβ foil filter. 1 Optical Spectroscopy. Optical diffuse-reflectance measurements were performed at room temperature using a Shimadzu UV-3600 UV vis-nir spectrometer from 200 to 1500 nm. BaSO 4 was used as the reflectance reference. The reflectance versus wavelength data were used to estimate the band gap of the material by converting reflectance to absorption data according to the Kubelka-Munk equation: F(R) = (1-R) 2 /2R, where R is the reflectance. 2 Photoluminescence spectra. Steady-state photoluminescence (PL) and temperature-dependent PL spectra were recorded using Horiba JobinYvon, LabRAM HR800 spectrometer and excited with a 340 nm laser using a liquid helium cooler. The PL emission (PLE) spectra were measured using a Hitachi F-7000 FL Spectrophotometer with a settled emission wavelength of 412 nm. It should be mentioned that due to the weak PL intensity of Cs 2 PbI 2 Cl 2, the excitation and emission splits were set to be relatively wide (5 nm here), and with a strong reflection of the excitation light from the single crystal facets, the PLE intensities near the emission position increased too much to be reliable. So we cut off the wavelength range at 402 nm where a seemingly PLE peak appeared (near the bandgap of ~3.04 ev) and the PL signals afterward were basically covered by the excitation light. The time-resolved PL (TRPL) spectra were measured using an Edinburgh Instruments FLS920 spectrometer by the time correlated single photon counting technique. An EPL nm pulsed diode laser with a ps pulse width was used for excitation and the emission wavelength was set at 412 nm. A peak intensity of 10 4 was reached to ensure the reliability of lifetime. IRF spectra were measured and a deconvolution fit mode with three lifetime parameters was used to fit the final decay curve. All measurements were performed using single crystal samples. Thermal analysis. Differential thermal analysis (DTA) were performed on a Shimadzu DTA-50 thermogravimetric analyzer in aluminum boats using α-al 2 O 3 as reference. Ground materials ( 30 mg) were S3

4 flame-sealed in a silica ampule evacuated to 10 3 mbar. Samples were heated and cooled at a speed of 10 C/min with a soaking time of 10 min when reaching the high or low temperature limits. Thermal gravimetric analysis (TGA) were performed using a platinum foil bucket and measured under a constant flow of nitrogen at a speed of 10 C/min. Photo Responsivity and Electrical Resistivity Measurements. Cs 2 PbI 2 Cl 2 single crystal with a dimension of mm 2 (plane) 1.5 mm was used. The interdigitated Au electrodes were deposited on the surface of Cs 2 PbI 2 Cl 2 with a thickness of 50 nm, composing of 20 channels with a size of 30 µm (width) 2 mm. UV light with a main emission peak at 365 nm was generated by a UV light source (MUA-165, MEJIRO GENOSSEN, emission spectrum shown in Figure S9), and the light intensity was calibrated by a hand-hold irradiatometer. The time dependent photocurrent curves were measured using a Keithley 4200 Semiconducting System with the LED light source (Model: T6, nm) controlled by a RIGOL (DG4162) Function/Arbitrary Waveform Generator. Alpha-Particle Responsivity Measurements. Cs 2 PbI 2 Cl 2 single crystal with a dimension of mm 2 (plane) 1.6 mm (thickness) was used. Two 50 nm Au patterns were deposited on the surface of Cs 2 PbI 2 Cl 2 ( mm 2 ) with a channel width of 1.6 mm and length of 3 mm (a scheme of electrode pattern is shown in Figure S12 inset). The α-particles source employed here was 1 µci 241 Am α-particles source with a kinetic energy of 5.49 MeV. During the measurement, the Cs 2 PbI 2 Cl 2 detectors were enclosed in a metal shielding box connecting to the ev-550 preamplifier. A positive bias was applied on the bottom contact while the α-particles were irradiated from the top cathode contact. The transient signals from the preamplifier were further amplified and shaped by the ORTEC amplifier (Model 572A) with a gain of and a shaping time of 1-10 µs. Then the signals were subsequently evaluated by a dual 16 K input multichannel analyzer (Model ASPEC-927) and read into the MAESTRO-32 software, which generated and displayed the response spectrum. Theoretical Calculation Methods Crystal structure optimization and electronic structure calculation were performed based on density function theory (DFT). The projector augmented-wave (PAW) method, as implemented in the Vienna ab initio simulation package 5.4 (VASP5.4), 3,4 was employed when dealing with ion-electron interaction. The lattice parameters and atomic coordinates were optimized until the calculated forces on each atom were smaller than 0.01 ev/a with a k-mesh of The energy convergence criterion and the energy cutoff of the plane-wave basis set were set to 10-5 ev and 600 ev, respectively. The band structure was calculated by using both Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional and HSE06 hybrid functional. 5 The spin-orbit coupling (SOC) was considered throughout the calculations. S4

5 Solid State Synthesis Figure S1 Schematic view of <100>-oriented (RP phase) 2D halide perovskites (right panel). The spacer and interlayer cations are both Cs + for all-inorganic RP phase, while for hybrid one, spacer cation A are long-chain organic amines and interlayer cation A are methylammonium, formamidinium or Cs +. S5

6 Figure S2 Experimental powder XRD results of solid state synthesis with the chemical composition of (a) Cs 2 PbCl 4, (b) Cs 2 PbBr 4, (c) Cs 2 PbI 4, (d) Cs 2 PbBr 2 Cl 2 and (e) Cs 2 PbI 2 Br 2. All the reactions generate products of CsPbX 3 + Cs 4 PbX 6 (X = Cl, Br, I or mixture of two neighboring halogen ions). Figure S3 (a) powder XRD patterns and (b) UV-Vis absorption of two typical Cs 2 PbI 2 Cl 2 samples obtained from solid state synthesis. Inset is the powder sample image. Impurities of CsPbI 3 and Cs 4 PbI 6 are always observed in the reaction products. S6

7 Figure S4 Two-cycle DTA measurement of Cs 2 PbI 2 Cl 2. Figure S5 (a) powder XRD patterns and (b) UV-Vis absorption before and after DTA measurement of Cs 2 PbI 2 Cl 2. S7

8 Figure S6 (a) Temperature-dependent PL, (b) PLE and (c) TRPL spectra of Cs 2 PbI 2 Cl 2 single crystals. S8

9 Crystallographic Data of Cs 2 PbI 2 Cl 2 Table S1. Crystal data and structure refinement for Cs 2 PbI 2 Cl 2. Empirical formula Cs 2 PbI 2 Cl 2 Formula weight Temperature 293(2) K Wavelength Å Crystal system Tetragonal Space group I4/mmm a = (8) Å, α = 90 Unit cell dimensions b = (8) Å, β = 90 c = (4) Å, γ = 90 Volume 600.2(2) Å 3 Z 2 Density (calculated) g/cm 3 Absorption coefficient mm -1 F(000) 664 Crystal size x x mm 3 θ range for data collection to Index ranges -7<=h<=7, -7<=k<=7, -25<=l<=22 Reflections collected 2382 Independent reflections 280 [R int = ] Completeness to θ = % Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 280 / 0 / 13 Goodness-of-fit Final R indices [I > 2σ(I)] R obs = , wr obs = R indices [all data] R all = , wr all = Extinction coefficient (2) Largest diff. peak and hole and e Å -3 R = Σ F o - F c / Σ F o, wr = {Σ[w( F o 2 - F c 2 ) 2 ] / Σ[w( F o 4 )]} 1/2 and w=1/[σ 2 (Fo 2 )+(0.0326P) P] where P=(Fo 2 +2Fc 2 )/3 S9

10 Table S2. Atomic coordinates (x10 4 ) and equivalent isotropic displacement parameters (Å 2 x10 3 ) for Cs 2 PbI 2 Cl 2 with estimated standard deviations in parentheses. Label x y z Occupancy * U eq Pb(01) (1) Cs(00) (1) 1 52(1) I(003) (1) 1 57(1) Cl(04) (2) * U eq is defined as one third of the trace of the orthogonalized U ij tensor. Table S3. Anisotropic displacement parameters (Å 2 x10 3 ) for Cs 2 PbI 2 Cl 2 with estimated standard deviations in parentheses. Label U 11 U 22 U 33 U 12 U 13 U 23 Pb(01) 19(1) 19(1) 41(1) Cs(00) 52(1) 52(1) 50(1) I(003) 65(1) 65(1) 42(1) Cl(04) 69(4) 17(2) 80(4) The anisotropic displacement factor exponent takes the form: -2π 2 [h 2 a *2 U hka * b * U 12 ]. Table S4. Selective bond lengths and bond angles for Cs 2 PbI 2 Cl 2 with estimated standard deviations in parentheses. Label Distances (Å) Label Angles ( ) Pb(01)-I(003) 3.171(2) I(003)-Pb(01)-I(003) Pb(01)-Cl(04) (4) I(003)-Pb(01)-Cl(04) 90.0 I(003)-Cs(00) 3.781(3) Cl(04)-Pb(01)-Cl(04) Pb(01)-Cl(04)-Pb(01) S10

11 Details of Theoretical Calculations Table S5. Crystal structures, GGA-PBE calculated total energies (E Total ) of all-inorganic RP phase lead halide perovskites and possible secondary phases. Compound Crystal system Space group E Total (ev/f.u.) Dataset ID α Cs 2 PbCl 4 tetragonal I4/mmm Cs 2 PbBr 4 tetragonal I4/mmm Cs 2 PbI 4 tetragonal I4/mmm Cs 2 PbBr 2 Cl 2 tetragonal I4/mmm Cs 2 PbI 2 Cl 2 tetragonal I4/mmm Cs 2 PbI 2 Br 2 tetragonal I4/mmm β-cs 2 PbBr 2 Cl 2 tetragonal I4/mmm β-cs 2 PbI 2 Cl 2 tetragonal I4/mmm β-cs 2 PbI 2 Br 2 tetragonal I4/mmm CsCl cubic Pm-3m sd_ CsBr cubic Pm-3m sd_ CsI cubic Pm-3m sd_ PbCl 2 orthorhombic pnma sd_ PbBr 2 orthorhombic pnma sd_ PbI 2 trigonal P-3m sd_ CsPbCl 3 cubic Pm-3m sd_ CsPbBr 3 orthorhombic pnma sd_ CsPbI 3 orthorhombic pnma sd_ Cs 4 PbCl 6 trigonal R-3c sd_ Cs 4 PbBr 6 trigonal R-3c sd_ Cs 4 PbI 6 trigonal R-3c sd_ α. Inorganic Solid Phases, SpringerMaterials (online database), Springer, Heidelberg (ed.) Springer Materials. S11

12 Table S6. Summary of the Calculated H d of nine possible RP phase lead halide perovskites (n = 1). Compound Decomposition Pathway H d (mev/f.u.) Cs 2 PbCl 4 Cs 2 PbBr 4 Cs 2 PbI 4 Cs 2 PbBr 2 Cl 2 Cs 2 PbI 2 Cl 2 Cs 2 PbI 2 Br 2 β-cs 2 PbBr 2 Cl 2 β-cs 2 PbI 2 Cl 2 β-cs 2 PbI 2 Br 2 2 CsCl + PbCl 2 (A) 452 2/3 CsPbCl 3 + 1/3 Cs 4 PbCl 6 (B) CsBr + PbBr 2 (A) 411 2/3 CsPbBr 3 + 1/3 Cs 4 PbBr 6 (B) CsI + PbI 2 (A) -44 2/3 CsPbI 3 + 1/3 Cs 4 PbI 6 (B) CsCl + PbBr 2 (A-1) CsBr + PbCl 2 (A-2) 505 2/3 CsPbCl 3 + 1/3 Cs 4 PbBr 6 (B-1) 43 2/3 CsPbBr 3 + 1/3 Cs 4 PbCl 6 (B-2) 2 2 CsCl + PbI 2 (A-1) CsI + PbCl 2 (A-2) 568 2/3 CsPbCl 3 + 1/3 Cs 4 PbI 6 (B-1) 111 2/3 CsPbI 3 + 1/3 Cs 4 PbCl 6 (B-2) 39 2 CsBr + PbI 2 (A-1) CsI + PbBr 2 (A-2) 526 2/3 CsPbBr 3 + 1/3 Cs 4 PbI 6 (B-1) -5 2/3 CsPbI 3 + 1/3 Cs 4 PbBr 6 (B-2) CsCl + PbBr 2 (A-1) CsBr + PbCl 2 (A-2) 347 2/3 CsPbCl 3 + 1/3 Cs 4 PbBr 6 (B-1) /3 CsPbBr 3 + 1/3 Cs 4 PbCl 6 (B-2) CsCl + PbI 2 (A-1) CsI + PbCl 2 (A-2) 85 2/3 CsPbCl 3 + 1/3 Cs 4 PbI 6 (B-1) /3 CsPbI 3 + 1/3 Cs 4 PbCl 6 (B-2) CsBr + PbI 2 (A-1) -6 2 CsI + PbBr 2 (A-2) 247 2/3 CsPbBr 3 + 1/3 Cs 4 PbI 6 (B-1) /3 CsPbI 3 + 1/3 Cs 4 PbBr 6 (B-2) -316 S12

13 Table S7. Comparison of calculated unit cell parameters from different models for Cs 2 PbI 2 Cl 2. Cell parameter Experimental Calculated from Cs 2 PbI 2 Cl 2 Calculated from K 2 NiF 4 Value Error (%) Value Error (%) a (Å) b (Å) c (Å) α ( ) β ( ) γ ( ) E Total (ev/f.u.) Table S8. Calculated unit cell parameters and lead halide bond length (Å) of all-inorganic RP phase lead halide perovskites from the model of Cs 2 PbI 2 Cl 2. In-plane Out-of-plane Compound a b c Pb-Cl Pb-Br Pb-I Pb-Cl Pb-Br Pb-I Cs 2 PbCl Cs 2 PbBr Cs 2 PbI Cs 2 PbBr 2 Cl Cs 2 PbI 2 Cl Cs 2 PbI 2 Br β-cs 2 PbBr 2 Cl β-cs 2 PbI 2 Cl β-cs 2 PbI 2 Br Table S9. Calculated effective mass of hole and electron for Cs 2 PbI 2 Cl 2 along different direction. Type Direction m*/m 0 a h b c a e b c S13

14 Figure S7 PBE+SOC calculated PDOS and charge density distribution of VBM and CBM of (a,b) Cs 2 PbI 2 Cl 2 and (c,d) β-cs 2 PbI 2 Cl 2. In (b) and (d), the color temperature represents different charge density, i.e. charge density increases from green to yellow to red. (e) Schematic comparison of the orbital coupling between Pb 6s - I 5p and Pb 6s Cl 3p. Higher orbital energy of I 5p results in higher antibonding states compared to Pb 6s and Cl 3p. S14

15 Supplementary Data of Electrical Resistivity, Photo- and α-particle-response Measurements Figure S8 (a) XRD measurement on the naturally exfoliated facet of Cs 2 PbI 2 Cl 2 single crystal, indicating a strong (00l) preference of in-plane growth as shown in (b) within a unit cell. Figure S9 Emission spectrum of the UV light source (MUA-165, MEJIRO GENOSSEN) used in the photo response measurements ( access Jan., 2018). S15

16 Figure S10 UV light On-off response tests of Cs 2 PbI 2 Cl 2 single crystal under 10 V in-plane bias voltage at different low frequencies. Figure S11 Response time analysis of the Cs 2 PbI 2 Cl 2 UV-light detector using a typical on-off cycle at different frequencies. T rise and T decay represent the time when the output current rises to 90% and decays to 10% of the saturated photocurrent, respectively. S16

17 Figure S12 In-plane measurement of 241 Am α-particle (E k = 5.49 MeV) response of Cs 2 PbI 2 Cl 2 single crystal under 40 V bias voltage shows a weak counting signal. Inset shows the in-plane configuration with Au electrode patterns. It should be mentioned that the distance between the electrodes is identical to the thickness of the detector. S17

18 Table S10. Crystal structure comparison between Cs 2 PbI 2 Cl 2 and Cs 2 SnI 2 Cl 2. 6 Empirical formula Cs 2 PbI 2 Cl 2 Cs 2 SnI 2 Cl 2 Temperature 293(2) K Wavelength Å Crystal system Tetragonal Space group I4/mmm a = b (Å) (8) (3) c (Å) (4) (1) α = β = γ ( ) 90 Volume (Å 3 ) Composition variations (Cs 2 SnI 2 Cl 2 and Rb-substituted case) Figure S13 powder XRD pattern of Rb 2 PbCl 2 I 2 sample, showing a composition of RbPbI 3 and Rb 3 PbI 5. Reference 1. Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A.; Puschmann, H. J Appl. Crystallogr. 2009, 42, (2), Kortüm, G.; Braun, W.; Herzog, G. Angew. Chem. Int. Edit 1963, 2, (7), Kresse, G.; Furthmuller, J. Phys. Rev. B Condens. Matter. 1996, 54, (16), Kresse, G.; Furthmüller, J., Comp. Mater. Sci. 1996, 6, (1), Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996, 77, (18), Li, J.; Stoumpos, C. C.; Trimarchi, G. G.; Chung, In; Mao, L.; Chen, M.; Wasielewski, M. R.; Wang, L.; Kanatzidis, (Submitted). S18