Effects of Fluorinated Aromatic Spacer in Ag–Bi Double Perovskite for X‑ray Detector

Silver–bismuth halide double perovskites have
recently emerged
as one of the most promising green candidates for X-ray detection.
However, their sensitivity still leaves behind the lead-based counterparts
owing to the poor intrinsic optoelectronic properties and challenging
crystal growth. Therefore, we conducted the space cation engineering
by introducing fluorinated aromatic spacers to silver–bismuth
perovskites, and the large (FPEA)4AgBiBr8 (FPEA+ is 4-fluorophenethyl­ammonium) single-crystals were
synthesized for the first time. The p−π coupling, large
dielectric constant, and strong interlayer binding were revealed by
ab initio calculation in this system. These effects further lead to
better crystal quality and electrical properties, which was confirmed
by the experimental characterizations. Consequently, X-ray detector
based on (FPEA)4AgBiBr8 single-crystal exhibits
low dark current as well as noise level and a good sensitivity of
27 μC Gyair–1 cm–2. This work reveals the effects of fluorinated aromatic spacer in
Ag–Bi double perovskite and offers an inspiring strategy for
materials design.