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- 저자 : Stoumpos, Constantinos C. (검색결과 3 건)
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Stoumpos, Constantinos C.,Frazer, Laszlo,Clark, Daniel J.,Kim, Yong Soo,Rhim, Sonny H.,Freeman, Arthur J.,Ketterson, John B.,Jang, Joon I.,Kanatzidis, Mercouri G. American Chemical Society 2015 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.137 No.21
<P>The synthesis and properties of the hybrid organic/inorganic germanium perovskite compounds, AGeI<SUB>3</SUB>, are reported (A = Cs, organic cation). The systematic study of this reaction system led to the isolation of 6 new hybrid semiconductors. Using CsGeI<SUB>3</SUB> (<B>1</B>) as the prototype compound, we have prepared methylammonium, CH<SUB>3</SUB>NH<SUB>3</SUB>GeI<SUB>3</SUB> (<B>2</B>), formamidinium, HC(NH<SUB>2</SUB>)<SUB>2</SUB>GeI<SUB>3</SUB> (<B>3</B>), acetamidinium, CH<SUB>3</SUB>C(NH<SUB>2</SUB>)<SUB>2</SUB>GeI<SUB>3</SUB> (<B>4</B>), guanidinium, C(NH<SUB>2</SUB>)<SUB>3</SUB>GeI<SUB>3</SUB> (<B>5</B>), trimethylammonium, (CH<SUB>3</SUB>)<SUB>3</SUB>NHGeI<SUB>3</SUB> (<B>6</B>), and isopropylammonium, (CH<SUB>3</SUB>)<SUB>2</SUB>C(H)NH<SUB>3</SUB>GeI<SUB>3</SUB> (<B>7</B>) analogues. The crystal structures of the compounds are classified based on their dimensionality with <B>1</B>–<B>4</B> forming 3D perovskite frameworks and <B>5</B>–<B>7</B> 1D infinite chains. Compounds <B>1</B>–<B>7</B>, with the exception of compounds <B>5</B> (centrosymmetric) and <B>7</B> (nonpolar acentric), crystallize in polar space groups. The 3D compounds have direct band gaps of 1.6 eV (<B>1</B>), 1.9 eV (<B>2</B>), 2.2 eV (<B>3</B>), and 2.5 eV (<B>4</B>), while the 1D compounds have indirect band gaps of 2.7 eV (<B>5</B>), 2.5 eV (<B>6</B>), and 2.8 eV (<B>7</B>). Herein, we report on the second harmonic generation (SHG) properties of the compounds, which display remarkably strong, type I phase-matchable SHG response with high laser-induced damage thresholds (up to ∼3 GW/cm<SUP>2</SUP>). The second-order nonlinear susceptibility, χ<SUB>S</SUB><SUP>(2)</SUP>, was determined to be 125.3 ± 10.5 pm/V (<B>1</B>), (161.0 ± 14.5) pm/V (<B>2</B>), 143.0 ± 13.5 pm/V (<B>3</B>), and 57.2 ± 5.5 pm/V (<B>4</B>). First-principles density functional theory electronic structure calculations indicate that the large SHG response is attributed to the high density of states in the valence band due to sp-hybridization of the Ge and I orbitals, a consequence of the lone pair activation.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2015/jacsat.2015.137.issue-21/jacs.5b01025/production/images/medium/ja-2015-01025x_0013.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja5b01025'>ACS Electronic Supporting Info</A></P>
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Trimethylsulfonium Lead Triiodide: An Air-Stable Hybrid Halide Perovskite
Kaltzoglou, Andreas,Stoumpos, Constantinos C.,Kontos, Athanassios G.,Manolis, Georgios K.,Papadopoulos, Kyriakos,Papadokostaki, Kyriaki G.,Psycharis, Vasilis,Tang, Chiu C.,Jung, Young-Kwang,Walsh, Aro ACS AMERICAN CHEMICAL SOCIETY 2017 Inorganic Chemistry Vol.56 No.11
<P>We report on the synthesis, characterization, and optoelectronic properties of the novel trimethylsulfonium lead triiodide perovskite, (CH3)(3)SPbI3. At room temperature, the air-stable compound adopts a hexagonal crystal structure with a 1D network of face-sharing [PbI6] octahedra along the c axis. UV-vis reflectance spectroscopy on a pressed pellet revealed a band gap of 3.1 eV, in agreement with first-principles calculations, which show a small separation between direct and indirect band gaps. Electrical resistivity measurements on single crystals indicated that the compound behaves as a semiconductor. According to multi-temperature single-crystal X-ray diffraction, synchrotron powder X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry, two fully reversible structural phase transitions occur at -5 and ca. -100 degrees C with reduction of the unit cell symmetry to monoclinic as temperature decreases. The role of the trimethylsulfonium cation regarding the chemical stability and optoelectronic properties of the new compound is discussed in comparison with APbI(3) (A = Cs, methylammonium, and formamidinium cation), which are most commonly used in perovskite solar cells</P>
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Mao, Lingling,Tsai, Hsinhan,Nie, Wanyi,Ma, Lin,Im, Jino,Stoumpos, Constantinos C.,Malliakas, Christos D.,Hao, Feng,Wasielewski, Michael R.,Mohite, Aditya D.,Kanatzidis, Mercouri G. American Chemical Society 2016 Chemistry of materials Vol.28 No.21
<P>Hybrid halide perovskites are emerging semiconducting materials, with a diverse set of remarkable optoelectronic properties. Besides the widely studied three-dimensional (3D) perovskites, two-dimensional (2D) perovskites show significant potential as photovoltaic (PV) active layers while exhibiting high moisture resistance. Here, we report two series of new 2D halide perovskite solid solutions: (HA)Pb1-xSnxI4 and (BZA)(2)Pb1-xSnxI4 (x = 1, 0.75, 0.5, 0.25, 0), where HA stands for the organic spacer histammonium and BZA stands for benzylammonium cations. These compounds are assembled by corner-sharing octahedral [MI6](4-) units stabilizing single-layered, anionic, inorganic perovskite sheets with organic cations filled in between. The optical band gaps are heavily affected by the M-I-M perovksite angles with the band gap steadily decreasing when the angle approaches 180 degrees, ranging from 2.18 eV for (BZA)(2)PbI4 to 2.05 eV for (HA)PbI4. We find an anomalous trend in electronic band gap in the mixed compositions (HA)Pb1-xSnxI4 and (BZA)(2)Pb1-xSnxI4. When Sn substitutes for Pb to form a solid solution, the band gap further decreases to 1.67 eV for (HA)SnI4. The minimum band gap is at x = 0.75 at 1.74 eV. For BZA, the irregular trend is more intense, as all the intermediate compounds (BZA)(2)Pb(1-x)SnxI(4) (x = 0.75, 0.5, 0.25) have even slightly lower band gaps than (BZA)(2)SnI4 (1.89 eV). DFT calculations confirm the pure Pb and Sn compounds are direct band gap semiconductors. Relatively shorter photoluminescence (PL) lifetime in (BZA)2PbI4 than (HA)PbI4 is observed, suggesting faster recombination rates of the carriers. Solution deposited thin films of (HA)PbI4 and (BZA)2PbI4 show drastically different orientations with (HA)PbI4 displaying a perpendicular rather than parallel growth orientation with respect to the substrate, which is more favorable for PV devices. The higher potential in PV applications of the HA system is indicated by device performance, as the champion air stable planar device with the structure ITO/PEDOT:PSS/2D-perovskite/PCBM/Al of (HA)PbI4 achieves a preliminary power conversion efficiency (PCE) of 1.13%, featuring an open-circuit voltage (VOC) of 0.91 V.</P>
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