Electronic properties of silver-bismuth iodide rudorffite nanoplatelets

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.