Formamidinium dopant effects on double perovskite Cs₂AgBiBr₆

Abstract

The optoelectronic properties of formamidinium CH(NH2)2+ (FA) doped double perovskite Cs2AgBiBr6 with corresponding formula Cs1.875FA0.125AgBiBr6 were investigated based on electronic structures and supercell models. The dopant formation energies, tolerance and octahedral factors support the doped structures are stable. FA dopant increases band gap about 0.15 eV without introducing dopant states in gap, but also increases the reduced effective masses, exciton binding energies, and elastic constants. However, it decreases exciton energies and charge carrier mobilities. Though the energy barriers among the different FA orientations in Cs1.875FA0.125AgBiBr6 are quite small (<30 meV), FA orientations in doped systems can remarkably impact on electron and hole mobilities.