Supporting Information. Ultralow Self-Doping in 2D Hybrid Perovskite Single. Crystals

Transcription

1 Supporting Information Ultralow Self-Doping in 2D Hybrid Perovskite Single Crystals Wei Peng,,, Jun Yin, Kang-Ting Ho, Olivier Ouellette, Michele De Bastiani, Banavoth Murali,,# Omar El Tall, Chao Shen, Xiaohe Miao, ǁ Jun Pan, Erkki Alarousu, Jr-Hau He, Boon S. Ooi, Omar F. Mohammed, Edward Sargent, and Osman M. Bakr,,,* Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal , Saudi Arabia KAUST Solar Center, King Abdullah University of Science and Technology (KAUST), Thuwal , Saudi Arabia KAUST Catalysis Center, King Abdullah University of Science and Technology (KAUST), Thuwal , Saudi Arabia Division of Computer, Electrical and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal , Saudi Arabia Analytical Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal , Saudi Arabia ǁ Imaging and Characterization Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal , Saudi Arabia Department of Electrical and Computer Engineering, University of Toronto, 10 King s College Road, Toronto, Toronto, Ontario M5S 3G4, Canada * (O.M.B) osman.bakr@kaust.edu.sa 1

2 Figure S1. The as-synthesized 2D perovskite crystals, showing random stack features of the perovskite layers and a rough morphology. Figure S2. XRD of the 2D perovskite single crystal powders (black line) and the calculated powder XRD pattern (blue line) from corresponding single crystal structure data. Figure S3. MAPbI 3 and MAPbBr 3 single crystals using the same device structure show much larger dark currents. Note: the deviation from linearity at biases close to zero could be the result of mobile ions or space charge effects. 2

3 Figure S4. Out-of-plane resistivity measurement of the 2D perovskite single crystals. The data shown here is measured in the PEA 2 PbI 4 single crystal and similar n=2 and 3. Such a large resistivity is mainly the result of the weak van der Waals force among perovskite layers. Indeed, extremely large conductivity anisotropy has been measured before. 1 The large conductivity anisotropy favors the model for our measurement and calculation of the sheet resistivity for 2D perovskite single crystals. Figure S5. a) Calculated band structure of MAPbI 3 in the tetragonal phase. b) Projected density of states of n=1, n=2, and n=3 2D perovskites calculated at GGA/PBE level without account of spin-orbit coupling. Table S1. Calculated effective mass (m*, m 0 ) and deformation potential (E I, ev) of n = 1, n = 2, n = 3, and MAPbI 3. Compounds n=1 n=2 n=3 CH 3 NH 3 PbI 3 Effective mass (m 0 ) Electron (Γ-F) (Γ-F) (Γ-F) Hole (Γ-F) (Γ-F) (Γ-F) (Γ-X) (Γ-Z) (Γ-M) (Γ-X) (Γ-Z) (Γ-M) Deformation Potential (ev) Electron Hole

4 Figure S6. a) Simulation of the conductivity behavior by considering only the carriers from dopants (extrinsic) and band-to-band (intrinsic) thermal excitation and temperature dependence of electronphonon scattering. It is worth noting that the simulation result is not the real conductivity value since a constant related to the real mobility value and other temperature-irrelevant constants are ignored to simplify the calculation of the temperature dependence of conductivity. In the equation (above the graph), N! e!!!!!" is the extrinsic carrier density, where N d is dopant concentration, E a is the dopant activation energy, k is Boltzmann constant, T is temperature. This calculation is just a rough expression of the dopant ionization probability. More precise expression of the free carrier concentration contributed by dopant ionization needs to be obtained from solving the neutrality equation. 2 m m!!! T 300!! !" e!!!!!" is the density of intrinsic carriers, where the density of states for band-to-band excitation is simplified by considering only the excitation of electrons at the valence band top, m is electron effective mass, m! is the electron mass, and E g is the band gap. The factor of T -3/2 describes the temperature dependence of carrier mobility through electron-phonon scattering. b) The ln σ T!! ~ 1 T plot of PEA 2 PbI 4 (n=1) and MAPbI 3. The dopant activation energy extracted from the slope of the linear regimes is also listed. Figure S7. The evolution of XRD patterns (intensity in log scale) of exfoliated PEA 2 PbI 4 crystal surface while storing in the air (50% RH), demonstrating decomposition (the diffraction peaks of the decomposition products were indicated by the arrows). 4

5 Figure S8. The topography images of a) fresh and b) aged exfoliated PEA 2 PbI 4 crystal surface by differential interference contrast optical microscopy. Figure S9. XRD pattern of spin-coated PEA 2 PbI 4 thin film. Figure S10. XRD (intensity in log scale) of spin-coated a) n=2 thin film and b) n=3 thin film and PL spectra of c) n=2 thin film and d) n=3 thin film. In both PL spectra, the major peaks at around nm don t correspond to the PL of n=2 and n=3 2D perovskites. We assume that these emission peaks are resulted from the complex charge carrier transfer and recombination dynamics between MAPbI 3 and 2D perovskites, or possible defect states (ref.). In both characterization techniques, mainly the phases of n=1 and MAPbI 3 are observed, which should result from a much lower solubility of PEA compared to MA, leading to the fast crystallization of n=1 2D perovskites in the beginning. The depletion of PEA cation in the beginning will result in the formation of only MAPbI 3 in the later crystallization process. This 5

6 mechanism can be also used to understand the large MA:PEA ratio (much larger than the stoichiometric ratio of the corresponding 2D perovskite products) in the single crystal growth recipe. Figure S11. I-V curves of spin-coated a) n=2 and b) n=3 thin film. Figure S12. I-V hysteresis behavior of devices based on a) fresh 2D perovskite single crystals, b) 3D perovskite single crystals, c) aged 2D perovskite single crystals, and d) 2D perovskite thin films. 6

7 Figure S13. Time-resolved PL decay of the 2D perovskite single crystals Reference: 1. Hong, X.; Ishihara, T.; Nurmikko, A. V., Photoconductivity and electroluminescence in lead iodide based natural quantum well structures. Solid State Communications 1992, 84 (6), Pierret, R. F., Semiconductor Device Fundamentals. Addison-Wesley: