69507-98-8Relevant articles and documents
Dynamic Optical Properties of CH3NH3PbI3 Single Crystals As Revealed by One- and Two-Photon Excited Photoluminescence Measurements
Yamada, Yasuhiro,Yamada, Takumi,Phuong, Le Quang,Maruyama, Naoki,Nishimura, Hidetaka,Wakamiya, Atsushi,Murata, Yasujiro,Kanemitsu, Yoshihiko
, p. 10456 - 10459 (2015)
The dynamic optical properties of perovskite CH3NH3PbI3 single crystals were studied by means of time-resolved photoluminescence (PL) spectroscopy at room temperature. The PL peak under one-photon excitation exhibits a red-shift with elapsing time, while two-photon PL is time-independent and appears at lower energy levels. The low-energy two-photon PL can be attributed to emissions from the localized states because of strong band-to-band absorption and photon re-absorption of the emitted light in the interior region. We revealed that the PL behaviors can be explained by the diffusion of photocarriers generated in the near-surface region to the interior region. The excitation fluence dependence of the one-photon PL dynamics is also discussed in terms of the electron-hole radiative recombination and carrier diffusion effects.
On the Demystification of “HPbI3” and the Peculiarities of the Non-innocent Solvents H2O and DMF
Daub, Michael,Hillebrecht, Harald
, p. 1393 - 1400 (2018)
Detailed investigations by XRD reveal that the precursor “HPbI3” that was obtained by reaction of aq. conc. hydroiodic acid HI and PbI2 in DMF is (CH3)2NH2PbI3. (CH3)2NH2+ is formed by solvent reaction as already described in the literature but not properly assigned. Attempts to synthesize HPbI3 by gas phase reaction of PbI2 with aq. conc. HI yielded light-yellow crystals of the oxonium salt H18O8Pb3I8 (Pbam, Z = 2, a = 10.075, b = 30.162, c = 4.5664 ?). The crystal structure of H18O8Pb3I8 consists of trimeric ribbons of edge-sharing PbI6 octahedra. These ribbons [Pb3I8]2– are separated by protonated fragments of crystalline ice [H18O8]2+ or (H2O)6(H3O+)2. H18O8Pb3I8 can also be precipitated from PbI2 and aq. conc. HI. H18O8Pb3I8 is not stable at room temperature but transforms within a few days to light-yellow (H3O)2x(H2O)2–2xPb1–xI2 with x ≈ 0.23 (R3m, Z = 3, a = 4.5554, c = 29.524 ?). The crystal structure represents a CdCl2-type layer structure with H2O/H3O+ in between. Charge compensation is achieved by Pb2+ vacancies. Via topotactic reaction (H3O)2x(H2O)2–2xPb1–xI2 releases H2O/HI and forms crystals of the pristine PbI2. All steps were characterized by P-XRD, IR/Raman spectra, and UV/Vis spectra. H18O8Pb3I8 acts as a precursor for the synthesis of MAPbI3 because the reaction with gaseous CH3NH2 yields MAPbI3, so it can mimic a composition “HPbI3”.
Cs/MAPbI3 composite formation and its influence on optical properties
Pawar, Vani,Kumar, Manish,Jha, Priyanka A.,Gupta,Jha, Pardeep K.,Singh, Prabhakar
, p. 935 - 942 (2019)
The stability issue is very critical for organic hybrid perovskite CH3NH3PbI3 to be used in solar cell applications; whereas CsPbI3 is reported to be more stable than that of CH3NH3PbI3. In the present work, we attempt to substitute Cs+ in the organic hybrid perovskite CH3NH3PbI3 matrix to form Csx(CH3NH3)1-xPbI3 with 0 ≤ x ≤ 0.4 in ambient conditions i.e., at room temperature and in air via solid state reaction route. The structural studies reveal presence of both CH3NH3PbI3 (tetragonal, I4/mcm) and CsPbI3 (orthorhombic, Pnma) phases for x > 0. It is appearing that partial solid solution formation has occurred up to x = 0.2 but for x > 0.2, the composite formation dominates. The optical band gap is slightly increased by ～0.02 eV with substitution. These compounds keep the basic feature of parent CH3NH3PbI3 along with stability of CsPbI3.
Orientation of organic cations in hybrid inorganic-organic perovskite CH3NH3PbI3 from subatomic resolution single crystal neutron diffraction structural studies
Ren, Yixin,Oswald, Iain W. H.,Wang, Xiaoping,McCandless, Gregory T.,Chan, Julia Y.
, p. 2945 - 2951 (2016)
We report the crystal growth of well-faceted single crystals of methylammonium lead iodide, CH3NH3PbI3, and detailed single crystal neutron diffraction structural studies aimed at elucidating the orientation of the methylammonium (CH3NH3+) cation in the tetragonal and cubic phases of the hybrid inorganic-organic perovskite. Room temperature experiments reveal a tetragonal structure where the protonated amine substituent (-NH3+) of the cation is disordered in four positions, each preferentially located near the neighboring iodine of the [PbI6] octahedra, while the methyl substituent (-CH3) is disordered in eight positions located near the body position of the unit cell. High temperature experiments show a cubic structure where the cation aligns along the [011] (edge), the [111] (diagonal), and the [100] (face) directions of the unit cell. The resulting site occupancy ratio suggests the CH3NH3+ cation resides primarily along the [011] direction, in agreement with reported DFT calculations. One important feature that was observed for both tetragonal and cubic structures measured at 295 and 350 K, respectively, is the middle point of the C-N bond being located off-center from the high symmetry sites in the crystal structure, induced by the formation of hydrogen bond-like interactions between the -NH3+ substituent of the organic cation and the iodine atoms of [PbI6] octahedra.
Effects of annealing temperature on stability of methylammonium lead iodide perovskite powders
Padchasri, Jintara,Yimnirun, Rattikorn
, p. 63 - 69 (2017/05/31)
The methylammonium lead iodide (CH3NH3PbI3 or MAPbI) material is currently investigated as active material in perovskite solar cells. Its stability, high optical band gap, low processing temperature and abundant elemental constituents provide numerous advantages over most powder absorber materials. In this work, the stability of MAPbI perovskite powders under different annealing temperature conditions was examined. X-ray diffraction (XRD) measurement demonstrated that the direct mixing synthesis method was able to produce a highly crystalline MAPbI material in a tetragonal phase structure. Thermal stability measurement based on the Simultaneous Thermal Analyzer (STA) indicated that the MAPbI was stable below 275 °C. The optical properties were characterized by employing refraction spectroscopy, which confirmed a direct bandgap of 1.53 eV in MAPbI perovskite powders. FT-Raman and XPS spectra confirmed the existence of organic groups. The annealing affected significantly the phase formation and stability of MAPbI. A small amount of lead iodide (PbI2), a product of the degradation, was observed with increasing annealing temperature. Therefore, a suitable annealing temperature should be chosen to produce MAPbI powders, which in turn will result in a high performance perovskite solar cell.
