Karakus Melike, Jensen Søren A, D'Angelo Francesco, Turchinovich Dmitry, Bonn Mischa, Cánovas Enrique
Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
J Phys Chem Lett. 2015 Dec 17;6(24):4991-6. doi: 10.1021/acs.jpclett.5b02485. Epub 2015 Dec 4.
The nature of the photoconductivity in solution-processed films of methylammonium lead iodide perovskite is investigated by determining the variation of the photoconductive response with temperature. Ultrabroadband terahertz (THz) photoconductivity spectra in the 0.3-10 THz range can be reproduced well by a simple Drude-like response at room temperature, where free charge carrier motion is characterized by an average scattering time. The scattering time determined from Drude fits in the 0.3-2THz region increases from ∼4 fs at 300 K (tetragonal phase; mobility of ∼27 cm(2) V(-1) s(-1)) to almost ∼25 fs at 77 K (orthorhombic phase, mobility of ∼150 cm(2) V(-1) s(-1)). For the tetragonal phase (temperature range 150 < T < 300 K) the scattering time shows a ∼T(-3/2) dependence, approaching the theoretical limit for pure acoustic phonon (deformation potential) scattering. Hence, electron-phonon, rather than impurity scattering, sets the upper limit on free charge transport for this perovskite.
通过测定光电导响应随温度的变化，研究了溶液法制备的甲脒碘化铅钙钛矿薄膜中的光电导性质。在室温下，0.3 - 10太赫兹（THz）范围内的超宽带太赫兹光电导光谱可以通过简单的类德鲁德响应很好地再现，其中自由电荷载流子的运动由平均散射时间表征。从0.3 - 2太赫兹区域的德鲁德拟合确定的散射时间从300 K（四方相；迁移率约为27 cm² V⁻¹ s⁻¹）时的约4飞秒增加到77 K（正交相，迁移率约为150 cm² V⁻¹ s⁻¹）时的近25飞秒。对于四方相（温度范围150 < T < 300 K），散射时间呈现出约T⁻³/²的依赖性，接近纯声学声子（形变势）散射的理论极限。因此，对于这种钙钛矿，电子 - 声子相互作用而非杂质散射决定了自由电荷传输的上限。
