• Johnston, Michael B.
• Lal, Snigdha
• Jin, Heon
• Putland, Benjamin W. J.
• Righetto, Marcello
• Snaith, Henry J.
• Motti, Silvia Genaro
• Sansom, Harry C.
• Herz, Laura M.

Abstract

Silver-bismuth-based perovskite-inspired materials (PIMs) are increasingly being explored as non-toxic materials in photovoltaic applications. However, many of these materials exhibit an ultrafast localization of photogenerated charge carriers that is detrimental for charge-carrier extraction. In this work, such localization processes are explored for thermally evaporated thin films of compositions lying along the (AgI) x (BiI 3 ) y series, namely BiI 3 , AgBi 2 I 7 , AgBiI 4 , Ag 2 BiI 5 , Ag 3 BiI 6 , and AgI, to investigate the impact of changing Ag + /Bi 3+ content. A persistent presence of ultrafast charge-carrier localization in all mixed compositions and BiI 3 , together with unusually broad photoluminescence spectra, reveal that eliminating silver will not suppress the emergence of a localized state. A weak change in electronic bandgap and charge-carrier mobility reveals the resilience of the electronic band structure upon modifications in the Ag + /Bi 3+ composition of the mixed-metal rudorffites. Instead, chemical composition impacts the charge-carrier dynamics indirectly via structural alterations: Ag-deficient compositions demonstrate stronger charge-carrier localization most likely because a higher density of vacant sites in the cationic sublattice imparts enhanced lattice softness. Unraveling such delicate interplay between chemical composition, crystal structure, and charge-carrier dynamics in (AgI) x (BiI 3 ) y rudorffites provides crucial insights for developing a material-by-design approach in the quest for highly efficient Bi-based PIMs.

Topics

• density
• perovskite
• impedance spectroscopy
• photoluminescence
• silver
• mobility
• thin film
• extraction
• chemical composition
• band structure
• Bismuth