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

Abstract

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.

Centimeter‐Sized Single Crystals of Two‐Dimensional Hybrid Iodide Double Perovskite (4,4‐Difluoropiperidinium)4AgBiI8 for High‐Temperature Ferroelectricity and Efficient X‐Ray Detection

“…This situation also occurs in similar compounds, such as (C 3 H 9 NI) 4 AgBiI 8 , [ 19 ] Cs 3 Bi 2 I 9 , [ 20 ] and (H 2 MDAP)BiI 5 . [ 21 ] In addition, the PDOS disclose that the valence band and conduction band origin is derived from I‐5p states, Bi‐6p and Ag‐4p, respectively (Figure S6, Supporting Information).…”

Halide perovskites: A dark horse for direct X‐ray imaging

“…Although the single crystal had a high bulk resistivity of 10 10 Ω cm and even better X-ray attenuation capacity than CZT, the detector generated a low sensitivity of 1 μC Gy air −1 cm −2 , probably as a result of the relatively high trap density (10 11 cm −3 ) and relatively low carrier mobility (1.42 cm 2 V −1 s −1 ). 83 Similarly, 1D (DMEDA) BiI 5 (DMEDA is N,N 0 -dimethylethanediamine) was developed. By applying an extremely high electrical field of 494 V mm −1 perpendicular to the chain of BiI 6 octahedra that isolated by DMEDA cations, the detector showed a sensitivity of 72.5 μC Gy air −1 cm −2 and dark current of 30 nA cm −2 .…”

“…For example, Tao et al reported a single‐crystalline (H 2 MDAP)BiI 5 (H 2 MDAP denotes N‐methyl‐1,3‐diaminopropanium) based X‐ray detector. Although the single crystal had a high bulk resistivity of 10 10 Ω cm and even better X‐ray attenuation capacity than CZT, the detector generated a low sensitivity of 1 μC Gy air −1 cm −2 , probably as a result of the relatively high trap density (10 11 cm −3 ) and relatively low carrier mobility (1.42 cm 2 V −1 s −1 ) 83 . Similarly, 1D (DMEDA)BiI 5 (DMEDA is N,N′‐dimethylethanediamine) was developed.…”

Lead-free halide perovskite Cs3Bi2Br9 single crystals for high-performance X-ray detection

“…[19] reported a solution-grown 0D MA 3 Bi 2 I 9 SC with an X-ray detection S as high as 10,620 μC Gy air −1 cm −2 . Furthermore, hybrid perovskite (BA) 2 CsAgBiBr 7 SCs (2D) and (H 2 MDAP)BiI 5 SCs (1D) have been successfully grown from a solution, and S of 4.2 and 1 μC Gy air −1 cm −2 were obtained, respectively [20,21].…”

“…In addition to the high S for X-ray detection, bismuth-halide perovskites with low dimensional structures exhibit high resistivity and very low ionic migration. This results in extremely low dark currents at the pA level and no drift, which is beneficial for an extremely low detectable dose rate [20][21][22][23]25]. (45), and is only slightly smaller than that of (NH 4 ) 3 Bi 2 I 9 (48.3) and Cs 3 Bi 2 I 9 (57.7).…”