Decreasing Structural Dimensionality of Double Perovskites for Phase Stabilization toward Efficient X‑ray Detection

Halide
double perovskites have attracted substantial attention
for optoelectronic applications owing to their low toxicity and high
stability. However, double perovskites have strict requirements in
terms of the halide type, thus rendering many of their properties
unchangeable, including the band gap, atomic number, and carrier transport.
By introducing long-chain organic amines, the chloride site of double
perovskites can be completely replaced by bromide. Using this strategy,
two dimensions silver–indium–bromide double perovskites
(PEA)4AgInBr8 and (i-BA)4AgInBr8 were successfully synthesized [(PEA)+ = C6H5(CH2)2NH3+, (i-BA)+ = CH­(CH3)2CH2NH3+]. Density
functional theory calculations and spectroscopy characterizations
were performed to unveil the semiconducting behaviors and photoluminescence
properties of the title compounds. Electrical characterization confirms
their good carrier-transport property (μτ product: 2.0
× 10–3 cm2 V–1) and low dark current. Moreover, the presence of heavy atoms, together
with the ultrastable baseline contributes to a high X-ray detection
sensitivity (185 μC Gyair–1 cm–2), greater than that of most previous double-perovskite
detectors. Our work lays the foundation for broadening the family
of potential double perovskites, creating a new path for the realization
of long-sought perovskites with low toxicity and high stability that
retain good optoelectronic performance.