Electronic Properties of Silver–Bismuth Iodide Rudorffite Nanoplatelets

Abstract

Silver−bismuth iodide (Ag−Bi−I) rudorffites are chemically stable and non-toxic materials that can act as a possible lead-free replacement for methylammonium lead halides in optoelectronic applications. We report on a simple route for fabricating Ag−Bi−I colloidal nanoplatelets approximately 160 nm in lateral dimensions and 1−8 nm in thickness via exfoliation of Ag−Bi−I rudorffite powders in acetonitrile. The valence band electronic structure of isolated Ag−Bi−I nanoplatelets was investigated using synchrotron radiation to perform X-ray aerosol photoelectron spectroscopy (XAPS). The ionization energy of the material was found to be 6.1 ± 0.2 eV with respect to the vacuum level. UV−vis absorption and photoluminescence spectroscopies of the Ag−Bi−I colloids showed that the optical properties of the nanoplatelets originate from I 5p to Bi 6p and I 5p to I 5p transitions, which is further confirmed by density functional theory (DFT) calculations. Finally, calculations based on the DFT and k • p theoretical methods showed that the quantum confinement effect is very weak in the system studied.