Single Perovskite or Double Perovskite: What’s the Difference?
Julian Steele a, Masoumeh Keshavarz b, Elke Debroye b, Haifeng Yuan b, Johan Hofkens b, Maarten Maarten a
a Centre for Surface Chemistry and Catalysis, KU Leuven, Celestijnenlaan 200F, Leuven, 3001, Belgium
b Department of Chemistry, KU Leuven, Celestijnenlaan 200F, Leuven, 3001, Belgium
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference on Perovskite and Organic Photovoltaics and Optoelectronics (IPEROP19)
Kyōto-shi, Japan, 2019 January 27th - 29th
Organizers: Hideo Ohkita, Atsushi Wakamiya and Mohammad Nazeeruddin
Oral, Julian Steele, presentation 072
Publication date: 23rd October 2018

The room-temperature charge carrier mobility and excitation-emission properties of metal halide perovskites are governed by the electronic band structure and intrinsic lattice phonon scattering mechanisms. Establishing how charge carriers interact within this scenario will have far-reaching consequences for developing high-efficiency materials for optoelectronic applications [1]. In this presentation, we evaluate the charge carrier scattering properties and conduction band environment of the double perovskite Cs2AgBiBr6 through a combinatorial approach; single crystal X-ray diffraction, optical excitation and temperature dependent emission spectroscopy, resonant and non-resonant Raman scattering, further supported by first principles calculations. We identify deep conduction band energy levels and that scattering from longitudinal optical phonons – via the Frӧhlich interaction – dominates electron scattering at room temperature, manifesting within the nominally non-resonant Raman spectrum as multiphonon processes up to the fourth order (Figure 1). We measure a Frӧhlich coupling constant nearing 230meV[2], which is inferred from a temperature dependent emission linewidth analysis. When compared to other more popular lead halide perovskites (40 - 60 meV [3]), the value measured here is giant, highlighting the fundamentally different nature of the two “single” and “double” perovskite materials branches.

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