Lim Vincent J-Y, Righetto Marcello, Farrar Michael D, Siday Thomas, Snaith Henry J, Johnston Michael B, Herz Laura M
Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, U.K.
School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, U.K.
ACS Energy Lett. 2025 Aug 28;10(9):4589-4595. doi: 10.1021/acsenergylett.5c02283. eCollection 2025 Sep 12.
Tin-halide perovskites currently offer the best photovoltaic performance of lead-free metal-halide semiconductors. However, their transport properties are mostly dominated by holes, owing to ubiquitous self-doping. Here we demonstrate a noncontact, optical spectroscopic method to determine the effective mass of the dominant hole species in FASnI, by investigating a series of thin films with hole densities finely tuned through either SnF additive concentration or controlled exposure to air. We accurately determine the plasma frequency from mid-infrared reflectance spectra by modeling changes in the vibrational response of the FA cation as the plasma edge shifts through the molecular resonance. Our approach yields a hole effective mass of 0.28 for FASnI and demonstrates parabolicity within ∼100 meV of the valence band edge. An absence of Fano contributions further highlights insignificant coupling between the hole plasma and FA cation. Overall, this approach enables noncontact screening of thin-film materials for optimized charge-carrier transport properties.
卤化锡钙钛矿目前在无铅金属卤化物半导体中具有最佳的光伏性能。然而，由于普遍存在的自掺杂现象，它们的输运特性大多由空穴主导。在此，我们展示了一种非接触式光谱方法，通过研究一系列通过SnF添加剂浓度或控制空气暴露来精细调节空穴密度的薄膜，来确定FASnI₃中占主导的空穴种类的有效质量。我们通过对FA阳离子的振动响应变化进行建模，从红外反射光谱中准确确定等离子体频率，因为等离子体边缘通过分子共振发生移动。我们的方法得出FASnI₃的空穴有效质量为0.28me，并且在价带边缘约100meV范围内显示出抛物线特性。不存在法诺贡献进一步突出了空穴等离子体与FA阳离子之间的微弱耦合。总体而言，这种方法能够对薄膜材料进行非接触式筛选，以优化电荷载流子的输运特性。
