Lattice Dynamics and Electron-Phonon Coupling in Lead-Free Cs2AgIn1-xBixCl6 Double Perovskite Nanocrystals.

Recently, lead free all-inorganic double perovskites have revolutionized the photovoltaic research, showing promising light emitting efficiency and tunability via modification of inherent structural and chemical properties. Here, we report a combined experimental and theoretical study on the variation of carrier-lattice interaction and optoelectronic properties of Cs2AgIn1-xBixCl6 double perovskite nanocrystals with varying alloying concentrations. Our UV-vis study confirms the parity allowed first direct transition for x ≤ 0.25. 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 (one for translational motion of ‘Cs’ and other for octahedral breathing), 1 Eg and 1 A1g mode for various stretching of Ag-Cl octahedra. Ab-initio simulation reveals dominant carrier-phonon scattering via Frohlich mechanism near room temperature, with longitudinal optical phonons being effectively act...