Abstract
Bandgap bowing has recently been emerged as an effective strategy toward band-engineering in metal halide perovskites. In this work, we report extensive studies on the bowing phenomenon in Cs2NaBiCl6 double perovskite upon alloying with silver at the sodium site. Through optical spectroscopy, composition-dependent bandgap in Cs2Na1−x Ag x BiCl6 (0 ⩽ x ⩽ 1) evidenced bandgap bowing with an upward-concave nature. Further from the quadratic fit, the bowing coefficient (b = 0.74 eV) turned out to be independent of composition and is close to the theoretically predicted value. From scanning tunneling spectroscopy and associated studies on band-energies, we have observed that the bandgap-lowering originated from a significant change of the valence-band position. The behavior of band-energies has been explained through the orbital-contributions of the constituent elements responsible in forming the two bands. Formation of an internal type-I band-alignment between the two end-members, namely Cs2NaBiCl6 and Cs2AgBiCl6 could be visualized. Based on experimental evidences, we could infer that the bow-like evolution of bandgap in Cs2Na1−x Ag x BiCl6 alloys is principally dominated by structural distortions in the Cs2NaBiCl6 host-lattice upon incorporation of silver.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
