Lead Free Alloyed Double Perovskites: An Emerging Class of Materials from Many-Body Perturbation Theory

The discovery of lead free all-inorganic alloyed double perovskites have revolutionized photovoltaic research, showing promising light emitting efficiency and its tunability. However, detailed studies regarding optical, exciton, polaron and transport properties remain unexplored. Here, we report a theoretical study on the variation of carrier-lattice interaction and optoelectronic properties of pristine as well as alloyed Cs$_2$AgInCl$_6$ double perovskites. We have employed many-body perturbation theory (G$_0$W$_0$@HSE06) and density functional perturbation theory (DFPT) to compute exciton binding energy (E$_\textrm{B}$) and exciton lifetime of different alloyed double perovskites. We find that phonon scattering limits charge-carrier mobilities and thus, plays an important role in the development of high-efficiency perovskite photovoltaics. In view of this, dominant carrier-phonon scattering is observed via Fr\"{o}hlich mechanism near room temperature. Moreover, we observe a noticeable increase in hole and electron mobilities on alloying. We believe that our results will be helpful to gain a better understanding of the optoelectronic properties and lattice dynamics of these double perovskites.