Novel Spin Physics in<scp>Organic–Inorganic</scp>Perovskites

Zhang, Chuang; Sun, Dali; Vardeny, Z. Valy

doi:10.1002/9783527800766.ch4_01

Cited by 3 publications

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“…The exceptionally high efficiency of thin-film solar cells based on lead halide perovskites (LHPs) − has triggered intense research activities on the physical mechanisms that give rise to their unusual material properties like long carrier lifetimes, − nontrivial spin dynamics, − and light-induced structural dynamics. − Accurate models of the underlying microscopic processes rely on precise measurements of material parameters such as the optical constants. However, measurement results spread widely, even for parameters as essential as the optical band gap of the prototypical LHP methylammonium lead iodide (CH 3 NH 3 )PbI 3 .…”

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Looking beyond the Surface: The Band Gap of Bulk Methylammonium Lead Iodide

et al. 2020

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Despite the intense research on photovoltaic lead halide perovskites, reported optical properties as basic as the absorption onset and the optical band gap vary significantly. To unambiguously answer the question whether the discrepancies are a result of differences between bulk and “near-surface” material, we perform two nonlinear spectroscopies with drastically different information depths on single crystals of the prototypical (CH3NH3)PbI3 methylammonium lead iodide. Two-photon absorption, detected via the resulting generation of carriers and photocurrents (2PI–PC), probes the interband transitions with an information depth in the millimeter range relevant for bulk (single-crystal) material. In contrast, the transient magneto-optical Kerr effect (trMOKE) measured in a reflection geometry determines the excitonic transition energies in the region near (hundreds of nm) the surface which also determine the optical properties in typical thin films. To identify differences between structural phases, we sweep the sample temperature across the orthorhombic–tetragonal phase transition temperature. In the application-relevant room-temperature tetragonal phase (at 170 K), we find a bulk band gap of 1.55 ± 0.01 eV, whereas in the near-surface region excitonic transitions occur at 1.59 ± 0.01 eV. The latter value is consistent with previous reflectance measurements by other groups and considerably higher than the bulk band gap. The small band gap of the bulk material explains the extended infrared absorption of crystalline perovskite solar cells, the low-energy bands which carry optically driven spin-polarized currents, and the narrow bandwidth of crystalline perovskite photodetectors making use of the spectral filtering at the surface.

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confidence: 99%

Looking beyond the Surface: The Band Gap of Bulk Methylammonium Lead Iodide

et al. 2020

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“…Интерес к данным материалам обусловлен набором особенных оптических и фотоэлектрических характеристик, которыми обладают МОП. В первую очередь это оптимальная, перестраиваемая в зависимости от состава перовскита, ширина запрещенной зоны, высокий коэффициент поглощения, нетривиальная динамика спина [10][11][12][13], индуцированная светом структурная динамика [14][15][16][17][18][19] и длительные времена жизни носителей заряда [20][21][22][23][24].…”

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Спектры пропускания монокристаллов гибридных перовскитов MAPbI-=SUB=-3-=/SUB=- вблизи края фундаментального поглощения

Аникеева¹,

Болдырев²,

Семенова³

et al. 2022

Оптика И Спектроскопия

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The paper presents the transmission spectra of hybrid perovskite MAPbI3 single crystals near the fundamental absorption edge in a wide temperature range. The absorption coefficient α of the single crystal samples is estimated at a temperature T = 150 K for the light with a photon energy E = 1.6 eV and at T = 40 K for E = 1.8 eV. The obtained values turned out to be several orders of magnitude smaller than the values of α for thin-film samples known from the literature. A sharp shift of the fundamental absorption edge by ~ 100 meV was observed at a temperature T1 = 160 K of the structural phase transition from the tetragonal to the orthorhombic phase. The temperature hysteresis of the shift of the fundamental absorption edge near T1 was recorded, which is characteristic of a first-order phase transition.

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