Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session X8: Organic Inorganic Perovskite SpintronicsFocus
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Sponsoring Units: DMP GMAG Chair: Oana Jurchescu, Wake Forest University Room: 304 |
Friday, March 18, 2016 8:00AM - 8:36AM |
X8.00001: Organometal Trihalide Perovskite Spintronics Invited Speaker: Dali Sun The family of organometal trihalide perovskite (OTP), CH3NH3PbX3 (where X is halogen) has recently revolutionized the photovoltaics field, and shows promise in applications such as solar energy harnessing, light emitting diodes, field effect transistors and laser action. The OTP spin characteristic properties are influenced by the large spin-orbit-coupling of the Pb atoms, and thus may offer a new class of semiconductors for spin-based applications. In this talk we will summarize the `magnetic field effect' on photocurrent and electroluminescence in OTP optoelectronic devices, and photoluminescence from OTP films [1]; and report more recent studies of pure spin-current and spin-aligned carrier injection in OTP spintronics devices using `spin-pumping' and `spin-injection', respectively. We measured relatively large inverse-spin-Hall effect using pulsed microwave excitation in OTP devices at resonance with a ferromagnetic (FM) layer, and giant magnetoresistance in OTP-based spin-valves. Our studies launch the field of OTP spintronics. [1] C. Zhang et al. Nat. Phys. 11, 427-434 (2015) [Preview Abstract] |
Friday, March 18, 2016 8:36AM - 8:48AM |
X8.00002: Magneto-optical properties of hybrid organic-inorganic perovskites Zhi-Gang Yu In semiconductors the k.p Hamiltonian played a central role in understanding material properties because the model parameters are directly related to experimental measurable properties. Here we construct a 8-band k.p Hamiltonian for tetragonal perovskites from both perturbation and group theories and determine the parameters from first-principles band-structure calculations and experiments. This Hamiltonian is then used to study conduction- and valence-band states as well as excitons under an arbitrary magnetic field. The calculated electron and hole g-factors can explain the exciton g-factors measured by magneto-absorption and magneto-luminescence and the field-dependent exciton energies are consistent with the high-field magneto-absorption experiment, which has been used to accurately determine the exciton binding energy. [Preview Abstract] |
Friday, March 18, 2016 8:48AM - 9:00AM |
X8.00003: Studies of Gilbert magnetization damping in NiFe/organometallic trihalide perovskite bilayers investigated by broadband ferromagnetic resonance Matthew Groesbeck, Dali Sun, Ryan McLaughlin, Chuang Zhang, Haoliang Liu, Zeev Valy Vardeny Organo-metallic trihalide perovskites (OTP) have recently been suggested as promising candidates for spintronics applications, motivated by the presence of strong spin-orbit coupling, and recent studies of spin dynamics in CH$_3$NH$_3$PbI$_3$. To help elucidate the spin transport properties in these materials, we have studied the Gilbert magnetization damping parameter in NiFe ferromagnetic films related to spin-pumping into adjacent OTP layers under ferromagnetic resonance (FMR) excitation conditions, using a broadband FMR detection system. We found an increase of the damping parameter associated with spin-pumping into the OTP. The obtained thickness-dependent results are compared to those of NiFe/Cu and NiFe/Pt bilayer structures, where spin transport characteristics are well-known. [Preview Abstract] |
Friday, March 18, 2016 9:00AM - 9:12AM |
X8.00004: Optical Generation of Ballistic and Diffusive Spin Currents in Organic-Inorganic Lead Halide Perovskites Junwen Li, Paul Haney Organic-inorganic halide perovskite solar cells have attracted enormous attention in recent years due to their remarkable photovoltaic power conversion efficiency. These materials should exhibit interesting spin-dependent properties as well, owing to the strong spin-orbit coupling and the broken inversion symmetry present at room temperature. In this work, we consider the spin-dependent optical response of CH$_3$NH$_3$PbI$_3$ on two distinct time scales. We first use density functional theory to compute the ballistic spin current injected by absorption of linearly polarized light. This spin current persists on a time scale of the momentum relaxation time. We then consider diffusive transport of photogenerated charge and spin for a thin perovskite layer with a passivated surface and an Ohmic, non-selective back contact. The spin densities and spin currents are evaluated by solving the drift-diffusion equations for a 3-dimensional Rashba model. We comment on the applications of optically excited spin densities and spin currents in these materials. [Preview Abstract] |
Friday, March 18, 2016 9:12AM - 9:24AM |
X8.00005: \textbf{Exciton spin dynamics in MAPbI}$_{\mathrm{\mathbf{3}}}$\textbf{ measured by Hanle effect} William Talmadge, Ruizhi Wang, Patrick Odenthal, Nathan Gundlach, Chuang Zhang, Dali Sun, Zeev Valy Vardeny, Yan (Sarah) Li The organic-inorganic hybrid perovskites have emerged as a highly promising class of semiconductors for photovoltaic applications. The properties responsible for the high photoconversion efficiency are under extensive investigation. There have; however, been fewer investigations of spin-dependent effects in this class of materials. We present energy dependent photoinduced Faraday rotation in polycrystalline thin film CH$_{\mathrm{3}}$NH$_{\mathrm{3}}$PbI$_{\mathrm{3}}$, which benefit from the band structure and optical selection rules. The Faraday rotation spectrum follows the exciton absorption band at low temperatures, indicating its excitonic origin. Through the Hanle effect, based on Faraday rotation, we found the coexistence of two spin components at 4 K, which was confirmed through time resolved measurements. [Preview Abstract] |
Friday, March 18, 2016 9:24AM - 9:36AM |
X8.00006: Photoexcited carrier spin dynamics in CH$_{\mathrm{3}}$NH$_{\mathrm{3}}$PbI$_{\mathrm{3}}$ Patrick Odenthal, Nathan Gundlach, William Talmadge, Ruizhi Wang, Chuang Zhang, Dali Sun, Zeev Valy Vardeny, Yan (Sarah) Li Metal halide perovskites have shown great promise for the field of spintronics due to their large tunable spin-orbit coupling, spin dependent optical selection rules and predicted electrically tunable Rashba band. The spin sensitive optical transitions allow optical spin orientation of carriers using circularly polarized light, and detection of the spin polarization via optical Faraday rotation measurement. We study carrier spin dynamics on solution-processed polycrystalline CH$_{\mathrm{3}}$NH$_{\mathrm{3}}$PbI$_{\mathrm{3}}$ films using time-resolved Faraday rotation (TRFR). TRFR reveals unexpected long spin lifetimes exceeding 1ns at 4K. This is significant given that Pb and I exhibit large spin-orbit coupling, which usually lead to fast spin relaxation. [Preview Abstract] |
Friday, March 18, 2016 9:36AM - 9:48AM |
X8.00007: Composition, Temperature, and Electric Field Dependence of Magneto-Optical Properties of Lead Halide Perovskites Ryan McLaughlin, Chuang Zhang, Dali Sun, Z. Valy Vardeny Organometallic Perovskites have received much attention in recent years due to their remarkable efficiency in photovoltaic cells, along with their highly tunable optical and electrical properties. It is an important goal to quantify and understand the effects of Spin-Orbit Coupling in Perovskite-based optoelectronic devices, which can be characterized by magneto-optical properties such as Kerr rotation and Faraday rotation. Here we use the Verdet constant to investigate the tunability of the Spin-Orbit coupling parameters of Organometallic Perovskites as a function of chemical composition, temperature, and electric field. [Preview Abstract] |
Friday, March 18, 2016 9:48AM - 10:00AM |
X8.00008: ABSTRACT WITHDRAWN |
Friday, March 18, 2016 10:00AM - 10:12AM |
X8.00009: \textbf{Neutron and X-Ray Scattering Studies of Hybrid Perovskites for Photovoltaic Applications} Michael Crawford, Pamela Whitfield, Niina Jalarvo, Georg Ehlers, Madhusudan Tyagi, Norman Herron, Lynda Johnson, William Guise, Ivan Milas, Yongqiang Cheng, Luke Daemen, Anibal Ramirez-Cuesta, Katharine Page, Xiaoping Wang, Feng Ye Hybrid perovskites (ABX$_{3})$ have attracted a great deal of attention recently as light absorbers for photovoltaics. In these materials the A site is occupied by organic cations, for example methyl ammonium (MA) or formamidinium (FA) cations, the B site is occupied by metals, for example Pb or Sn, and the X anions are halogens (I, Br, or Cl). Typical of perovskites, these materials exhibit a series of structural phase transitions involving rotations or tilts of the BX$_{6}$ octahedra, but with the added complexity that the inorganic framework is coupled to order-disorder transitions of the organic cations. We have used neutron scattering techniques to characterize the structures and dynamics of several of these compounds as a function of temperature. In addition, high resolution synchrotron x-ray diffraction measurements have been performed to investigate the structural phase transitions. These studies yield a detailed picture of the structures, dynamics, and structural phase transitions of these compounds, and provide a firm basis for understanding their excellent photovoltaic properties. [Preview Abstract] |
Friday, March 18, 2016 10:12AM - 10:24AM |
X8.00010: Electric Field Effects on Photoconductivity and Photoluminescence in MAPbI$_{\mathrm{3}}$ Perovskite Chuang Zhang, Dali Sun, Zeev Valy Vardeny The origin of ``hysteresis behavior'' in I-V response of MAPbI$_{\mathrm{3}}$ perovskite devices is still under debate. We characterized this electric field induced hysteresis by monitoring the changes of photoconductivity (E-PC) and photoluminescence (E-PL) from the MAPbI$_{\mathrm{3}}$ film deposited on inter-digital electrodes. Interestingly, we observed a ``sign change'' in both E-PC and E-PL effects, depending on the applied field and temperature. The E-PC/E-PL could be ``frozen'' when cooling the device under external field to lower temperature. These results reveal multiple possible reasons for the intrinsic hysteresis behavior in MAPbI$_{\mathrm{3}}$ perovskite devices. This work was supported by the Utah NSF-MRSEC program DMR 1121252. [Preview Abstract] |
Friday, March 18, 2016 10:24AM - 10:36AM |
X8.00011: Nanoimprinting Perovskite by Hot Stamping for Improved Crystallinity and Morphology Balasubramaniam Balachandran, Ross Haroldson, Yixin Ren, Anvar Zakhidov, Wenchuang Hu, Julia Chan We present an innovative approach of using thermal nanoimprinting lithography (NIL by hot embossing) to pattern hybrid perovskites into ordered micro and nanostructures with improved crystallinity and morphology. The spin-coated thin films of organic-inorganic perovskite CH3NH3PbI3 have been embossed by large area stamps of highly periodic nanopatterns at the scale of 200 to 600 nm. XRD shows the larger and aligned grains, while SEM reveals much improved film morphology with no pin-holes and much less grain boundaries. The obtained ordered periodic micro- and nanostructures show iridescent coloration due to Bragg scattering in planar perovskite photonic crystals. [Preview Abstract] |
Friday, March 18, 2016 10:36AM - 10:48AM |
X8.00012: Spatially resolved optoelectronic characterization of perovskite lead iodide nanostructures Rui Xiao, Xingyu Peng, Yasen Hou, Dong Yu The high power conversion efficiency of organo-lead halide perovskite-based solar cells has attracted world-wide attention over the past few years. The high efficiency was believed to originate from the unusual properties including long carrier lifetimes and consequent long carrier diffusion lengths in these materials. Ion drift, ferroelectricity, and charge traps have been proposed to account for the efficient charge separation and photocurrent hysteresis. However, it remains unclear which mechanism is dominating. We fabricate field effect transistors (FETs) incorporating single nanoplates/nanowires of organic perovskite and perform scanning photocurrent microscopic (SPCM) measurements to extract carrier diffusion lengths as a function of gate voltage, source-drain bias. Spatially resolved optoelectronic investigations of single crystalline perovskite nanostructures provide valuable information and key evidence on distinguishing the dominating charge transport/separation mechanism. [Preview Abstract] |
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