- Dynamic Optical Properties of CH3NH3PbI3 Single Crystals As Revealed by One- and Two-Photon Excited Photoluminescence Measurements
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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.
- Yamada, Yasuhiro,Yamada, Takumi,Phuong, Le Quang,Maruyama, Naoki,Nishimura, Hidetaka,Wakamiya, Atsushi,Murata, Yasujiro,Kanemitsu, Yoshihiko
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- Colorimetric polarity chemosensor based on a organometal halide perovskite functional dye
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We have investigated polarity sensing of organometal halide CH3NH3PbI3 perovskite functional dye based on hydrogen bonds between alcohols and polar units in perovskite. Upon exposure of alcohol solvents, perovskite film showed a drastic visible color change with different changing time depending on the polarities of alcohols. From the kinetic study of the reaction between perovskite dye and alcohols having different polarities, efficiency of hydrogen-bonding interactions between them were clearly revealed to be the main sensing mechanism, which enables effective discrimination of polarities by naked eyes. This study suggests a novel and practical sensing platform for highly sensitive colorimetric polarity chemosensors.
- Kim, Jong H.,Kim, Sung-Hoon
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- On the Demystification of “HPbI3” and the Peculiarities of the Non-innocent Solvents H2O and DMF
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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”.
- Daub, Michael,Hillebrecht, Harald
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- Random lasing in organo-lead halide perovskite microcrystal networks
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We report optically pumped random lasing in planar methylammonium lead iodide perovskite microcrystal networks that form spontaneously from spin coating. Low thresholds (2) and narrow linewidths (Δλ 100 μm and spatially overlap with one another, resulting in chaotic pulse-to-pulse intensity fluctuations due to gain competition. These results demonstrate this class of hybrid organic-inorganic perovskite as a platform to study random lasing with well-defined, low-level disorder, and support the potential of these materials for use in semiconductor laser applications.
- Dhanker,Brigeman,Larsen,Stewart,Asbury,Giebink
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- Cs/MAPbI3 composite formation and its influence on optical properties
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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.
- Pawar, Vani,Kumar, Manish,Jha, Priyanka A.,Gupta,Jha, Pardeep K.,Singh, Prabhakar
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- Loading of mesoporous titania films by CH3NH3PbI3 perovskite, single step vs. sequential deposition
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Infiltration of mesoporous TiO2 scaffolds by CH3NH3PbI3 is more complete when using sequential compared to single step deposition processing and avoids formation of disordered capping layers affording greatly im
- Yantara, Natalia,Sabba, Dharani,Yanan, Fang,Kadro, Jeannette M.,Moehl, Thomas,Boix, Pablo P.,Mhaisalkar, Subodh,Gr?tzel, Michael,Gr?tzel, Carole
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- Orientation of organic cations in hybrid inorganic-organic perovskite CH3NH3PbI3 from subatomic resolution single crystal neutron diffraction structural studies
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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.
- Ren, Yixin,Oswald, Iain W. H.,Wang, Xiaoping,McCandless, Gregory T.,Chan, Julia Y.
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- Ultra-high Seebeck coefficient and low thermal conductivity of a centimeter-sized perovskite single crystal acquired by a modified fast growth method
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A centimeter-sized organic-inorganic hybrid lead-based perovskite CH3NH3PbI3 (MAPbI3) single crystal was obtained by using a modified fast and inverse-temperature growth method. The optical properties of this single crystal at room and low temperatures were studied in terms of optical absorption and photoluminescence measurements. The single crystal exhibited optical properties with a band-gap of 1.53 eV, which is comparable to a reported value. The temperature-dependent UV-vis spectra of this perovskite single crystal showed a unique structural phase transition as the temperatures varied. The thermoelectric properties of this MAPbI3 single crystal were studied, showing that the Seebeck coefficient of 920 ± 91 μV K?1 almost remained unchanged from room temperature to 330 K and it progressively increased with the increase in temperature and reached 1693 ± 146 μV K?1 at 351 K. In contrast, there was no very clear trend for thermal conductivities with changes in temperature. The thermal conductivities were maintained between 0.30 and 0.42 W m K?1 in the temperature range of 298-425 K. These thermoelectric characteristics would be useful for potential thermoelectric applications if the electrical conductivity of this crystal is improved by tuning its composition.
- Ye, Tao,Wang, Xizu,Li, Xianqiang,Yan, Alex Qingyu,Ramakrishna, Seeram,Xu, Jianwei
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p. 1255 - 1260
(2017/02/10)
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- Effects of annealing temperature on stability of methylammonium lead iodide perovskite powders
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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.
- Padchasri, Jintara,Yimnirun, Rattikorn
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- Towards toxicity removal in lead based perovskite solar cells by compositional gradient using manganese chloride
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We report synthetic steps towards a lead free manganese based perovskite MAPbxMn1-xI1+2xCl2-2x (nominal x = 0.1-1.0), photovoltaic material via a solid state reaction. Further application as an excellent panchromatic light harvester involves the fabrication of a cell with an inverted planar architecture at low processing temperature. This novel perovskite material offers an outstanding Voc of 1.19 V with fill factor of 87.9%.
- Singh, Pallavi,Rana, Prem Jyoti Singh,Dhingra, Pankul,Kar, Prasenjit
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supporting information
p. 3101 - 3105
(2016/05/10)
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- Chemical decoration of CH3NH3PbI3 perovskites with graphene oxides for photodetector applications
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A facile in situ solution method was developed for chemical decoration of CH3NH3PbI3 perovskites with reduced graphene oxides (rGOs) to significantly improve the photodetector performance. Such CH3NH3PbI3/rGO molecular hybrids show a 6 times higher ON/OFF ratio and notably faster response speed than neat CH3NH3PbI3.
- He, Minhong,Chen, Yani,Liu, Hui,Wang, Jialin,Fang, Xiaosheng,Liang, Ziqi
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supporting information
p. 9659 - 9661
(2016/01/09)
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- Properties of CH3NH3PbX3 (X = I, Br, Cl) powders as precursors for organic/inorganic solar cells
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CH3NH3PbX3 (X = Cl, Br, I) perovskites were prepared by a self-organization processes using different precursor solutions. The XRD analysis indicates the formation, at room temperature, of a tetragonal structure (space group I4/mcm) for X = I, of a cubic structure (space group Pm3m) for X = Br, and of centro-symmetric cubic structure (space group Pm3m) for X = Cl, respectively. The structural analysis revealed the formation of CH3NH3Cl as secondary phase in the Cl-containing system. The morphological investigation revealed the formation of rhombo-hexagonal dodecahedra crystallite for X = I, Br, whereas cube-like aggregates were observed for X = Cl. The thermogravimetric analysis performed in air did not reveal any loss until 250 °C for X = I and 300 °C for X = Br, respectively, whereas the differential thermal analysis (DTA) detected two endothermic thermal events (at 336 and 409 °C) for X = I and one only (379 °C) for X = Br, respectively. The infrared spectra (IR) of the powders conformed to the 3-fold symmetry of the methylammonium ion which rotates around the C-N axis. Optical absorption measurements indicated that the CH3NH3PbX3 systems behave as direct-gap semiconductors with energy band gaps of 1.53 eV for X = I, 2.20 eV for X = Br, and 3.00 eV for X = Cl, respectively, at room temperature. The direct-gap semiconductivity for X = I and X = Br was confirmed by the photoluminescence emission measurements, whereas the compound for X = Cl is inactive. I-containing powders were dissolved in an organic solvent (dimethyl-formamide, DMF). The dispersion (100-300 μL) was dropped on glassy substrates on which thick films were obtained by spin-coating and thermal treatment at 120 °C for ca. 5 min. The preparation of the layers was performed in air at room temperature.
- Dimesso,Dimamay,Hamburger,Jaegermann
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p. 6762 - 6770
(2015/02/18)
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- Systematic studies on chain lengths, halide species, and well thicknesses for lead halide layered perovskite thin films
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Two-dimensional layered perovskite compounds, (CnH 2n+1NH3)2(CH3NH3) m-1PbmX3m+1 (n = 2, 3, 4, 6, and 10; X = Cl, Br, and I; m = 1, 2, and 3) were systematically prepared. The influences of the barrier-size, halide species, and well thickness of the perovskite thin films on the quantum confinement structures were investigated. The layered perovskite films showed a strong and clear absorption peak due to excitons confined in inorganic quantum-wells. The exciton peak shifted to lower energy as the halide species was changed from Cl to Br and I. Furthermore, fine multilayer perovskite compound films were prepared by varying the spin-coating conditions.
- Takeoka, Yuko,Asai, Keisuke,Rikukawa, Masahiro,Sanui, Kohei
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p. 1607 - 1613
(2007/10/03)
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- Comparative study on the excitons in lead-halide-based perovskite-type crystals CH3NH3PbBr3 CH3NH 3PbI3
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Optical absorption and magnetoabsorption spectra of the lead-halide-based perovskite-type crystals, CH3NH3PbX3 (X = Br, I) have been investigated. The lowest-energy excitons in these crystals are normal three-dimensional Wannier-type excitons. Bohr radii, binding energies, reduced masses, effective g factors, and oscillator strengths of the excitons have been determined with satisfactory accuracy. A larger bandgap and more tightly bound nature of the excitons in CH3NH3PbBr 3 compared to those in CH3NH3PbI3 are a natural consequence of the halogen substitution.
- Tanaka, Kenichiro,Takahashi, Takayuki,Ban, Takuma,Kondo, Takashi,Uchida, Kazuhito,Miura, Noboru
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p. 619 - 623
(2008/10/08)
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- Electronic structures of lead iodide based low-dimensional crystals
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The electronic structures of three-dimensional and two-dimensional lead-halide-based crystals CH3NH3PbI3 and (C4H9NH3)2PbI4 are investigated by photoelectron spectroscopy and band calculations using the linear combination of atomic orbitals within the density-functional theory. For both crystals, the top of the valence band is found to consist mainly of the ?-antibonding states of Pb 6s and I 5p orbitals, and the bottom of the conduction band to be composed primarily of the ?-antibonding states of Pb 6p and I 5s orbitals. Photoelectron spectra of the valence-band region indicate that the electronic structures change depending on the dimensionality of the crystals. Based on the calculation results, the differences observed in the spectra are rationalized in terms of narrowing bandwidth as the dimensionality decreases from three to two dimensions. It is shown that the bandwidth narrowing of the two-dimensional crystal is due to zero dispersion in the vertical direction and the Jahn-Teller effect in the layered structure. These effects lead to a wideband gap and high exciton stability in (C4H9NH3)2PbI4.
- Umebayashi, T.,Asai, K.,Kondo, T.,Nakao, A.
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- Calorimetric and IR spectroscopic studies of phase transitions in methylammonium trihalogenoplumbates (II)
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Heat capacities of CH3NH3PbX3 (X = Cl, Br, I) were measured between 13 and 300 K (365 K for the iodide). Two anomalies were found in the chloride and the iodide, and three in the bromide. All the phase transitions were of
- Onoda-Yamamuro, Noriko,Matsuo, Takasuke,Suga, Hiroshi
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p. 1383 - 1396
(2008/10/08)
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- ALKYLAMMONIUM LEAD HALIDES. PART 1. ISOLATED PbI64- IONS IN (CH3NH3)4PbI6*2H2O
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The yellow (HH3NH3)4PbI6*2H2O (P21/n, a=10.421(3) Angstroem, b=11.334(2) Angstroem, c=10.668(2) Angstroem β=91.73(2) deg, Z=2) contains isolated PbI64- octahedra, CH3NH3+ cations of two types and H2O molecules.The cations and water molecules are hydrogen-bonded to form cat1...H2O...cat2 units arranged in centrosymmetric (cat1...H2O...cat2)24+ pairs; the centres of these composite units and the Pb atoms form a distorted NaCl-type lattice.The Pb-I bond length in the PbI64- anions are compared with those in ε complexes containing shared I atoms and the effect of sharing on the bond lengths is discussed.A scheme is proposed for the extensive three-dimensional hydrogen bonding in the structure.
- Vincent, Beverly R.,Robertson, Kaerine N.,Cameron, T. Stanley,Knop, Osvald
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p. 1042 - 1046
(2007/10/02)
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- Dynamic disorder in methylammoniumtrihalogenoplumbates (II) observed by millimeter-wave spectroscopy
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The temperature-dependent structure of crystalline methylammoniumtrihalogenoplumbates (II)-CH3NH+3 PbX-3 (X = Cl, Br, I)-as determined by x-ray diffraction, is compared with measurements of the temperature-dependent complex permittivity at frequencies of 50-150 GHz.The dielectric measurements reveal a picosecond relaxation process which corresponds to a dynamic disorder of the methylammonium group in the high-temperature phases of the trihalogenoplumbates.
- Poglitsch, A.,Weber, D.
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p. 6373 - 6378
(2007/10/02)
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