Study the optical properties of Cs₃CeI₆: First-principles calculations

The band structure, density of states, and optical properties of a novel material, Cs3CeI6 are calculated for the first time using the density functional theory method in first-principles calculations. It is found that Cs3CeI6 possesses a direct bandgap with an energy value of 3.05 eV. Examination of the density of states indicates that the conduction band minimum is primarily composed of Ce-5d and Ce-4f orbitals, while the valence band maximum is mainly contributed by Ce-4f orbitals. Photoluminescence (P.L.) spectroscopy reveals distinctive bimodal emission peaks at 432 and 468 nm, which serve as characteristic signatures of Ce3+ ions. This bimodal emission arises from spontaneous radiative transitions between excited 5d orbitals and the 2F(7/2) and 2F(5/2) states within the 4f orbital, as confirmed by crystal field calculations. The difference between these two emission peaks corresponds to variations in energy levels associated with Ce3+ ions due to crystal field disturbances. Moreover, Cs3CeI6 exhibits an exciton binding energy of 225 meV due to strong localization effects in Ce-4f orbitals and binding properties inherent in its zero-dimensional structure, promoting exciton formation. Such a substantial exciton binding energy offers significant advantages for potential electroluminescence applications. Based on these findings, we anticipate promising prospects for the use of Cs3CeI6 in electroluminescent devices.