Lattice Dynamics and Electron−Phonon Coupling in Lead-Free Cs2AgIn1−xBixCl6 Double Perovskite
Aftab Alam a, Debjit Manna b, Jiban Kangsabanik a, TK Das b, Aswani Yella b
a IIT Indian Institute of Technology Bombay, India, Powai, Mumbai, Mumbai, India
b Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, India, Powai, Mumbai, Maharashtra, India, Mumbai, India
Proceedings of Online Conference on Perovskites for Energy Harvesting: From Fundamentals to Devices (PERENHAR)
Online, Spain, 2020 November 19th - 20th
Organizers: Dinesh Kabra, Sandheep Ravishankar, Angshuman Nag and Priya Mahadevan
Invited Speaker, Aftab Alam, presentation 055
Publication date: 2nd November 2020

Recently, lead free all-inorganic double perovskites have revolutionized photovoltaic research, showing promising light emitting efficiency and tunability via modification of inherent structural/chemical properties. Carrier-lattice interactions via Frohlich mechanism is known to be the dominant scattering mechanism, dictating carrier mobility near room temperature for these compounds. In this talk, I will present a combined theoretical and experimental study on the variation of carrier-lattice interaction and optoelectronic properties of Cs2AgIn1-xBixCl6 double perovskite with varying alloying concentration. Using a careful analysis of Raman spectra assisted with first-principles simulations, we assign the possible three types of active modes to intrinsic atomic vibrations; 2 T2g modes, 1 Eg and 1 A1g for various stretching of Ag-Cl octahedra. Ab-initio simulation reveals dominant carrier-phonon scattering via Fröhlich mechanism near room temperature, with longitudinal optical phonons being effectively activated around 230 K. We observe a noticeable increase in hole mobility with small Bi alloying (~4 times). This is attributed to the valence band maxima acquiring Bis orbital characteristics, thus increasing its dispersive nature. We believe that our results should help to gain a better understanding of the intrinsic electronic and lattice dynamical properties of similar class compounds. Reference(s):

[3] Debjit Manna, J. Kangsabanik, T K Das, D Das, Aftab Alam, A. Yella, A. Alam, J. Phys. Chem. Lett. 11, 2113-2120 (2020).

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