A Lead-Free Hybrid Iodide with Quantitative Response to X‑ray Radiation

Single crystals of
lead halide hybrid perovskites (e. g., CH3NH3PbI3 and CsPbBr3) have
been developed as promising candidates for X-ray detection, owing
to their excellent attributes including low trap density, high X-ray
absorption cross section, and high carrier mobility. The toxicity
of lead, however, is a potential bottleneck that hinders their device
application toward green and sustainable competitors. Herein, we reported
a new lead-free bismuth-iodide hybrid of (H2MDAP)­BiI5 (1, H2MDAP = N-methyl-1,3-diaminopropanium),
adopting one-dimensional (1D) metal-halogen frameworks, which behaves
as a potential alternative for X-ray detection. Large-size single
crystals of 1 with sizes up to 9 × 7 × 4 mm3 were successfully grown via top-seeded solution growth method.
The as-grown crystal exhibits notable semiconducting properties, including
a narrow bandgap of 1.83 eV, trap density of 3.6 × 1011 cm–3, carrier mobility of 1.42 cm2 V–1 s–1, and high X-ray absorption
coefficient. Consequently, the fabricated crystal-based X-ray photoconductor
enables the conversion of X-ray to electrical signals with a sensitivity
of ∼1.0 μC Gyair–1 cm–2. These results throw light on further exploration
on X-ray-sensitive materials based on the lead-free metal halogen
hybrids.