Face‑/edge‑shared 3D perovskitoid single crystals with suppressed ion migration for stable X‑ray detector

As X-ray detection plays an indispensable role in industrial inspection, medical diagnosis, and security checks, the search for high-performance detection materials has never been more critical. Traditional three-dimensional (3D) metal halide perovskites show great promise for direct X-ray detection, yet their inherent ion migration severely undermines detector stability—hindering commercialization. Now, a collaborative team of researchers from institutions including Henan University, Shenzhen Institute of Advanced Technology (Chinese Academy of Sciences), and Shaanxi Normal University has developed a game-changing solution: face-/edge-shared 3D heterometallic glycinate hybrid perovskitoid single crystals (SCs) with suppressed ion migration. Their findings, published in Nano-Micro Letters, offer a new pathway for stable, high-sensitivity X-ray detection.

Why These 3D Perovskitoid SCs Stand Out

The core innovation lies in the unique design of the perovskitoid crystals, which addresses the long-standing ion migration issue of traditional perovskites while preserving key detection capabilities:

• Synergistic Ion Migration Suppression: The crystals (formula: Pb₂​CuGly₂​X₄​, where Gly=−O₂​C−CH₂​−NH₂​ and X=Cl/Br) feature a robust structure: large-sized Cu(Gly)₂​ pillars link adjacent lead halide layers, while a face-/edge-shared inorganic skeleton (composed of [PbX₅​O₃​]₉− dodecahedrons) adds rigidity. Together, these components boost the ion migration activation energy (Ea​) to 1.06 eV for the Cl-based variant—far higher than that of conventional 3D perovskites—effectively curbing ion movement.
• Ultra-Low Dark Current Drift: Under harsh conditions (120 V mm⁻¹ electric field and 2.86 Gy continuous X-ray irradiation), the Pb₂​CuGly₂​Cl₄​ SC detector exhibits an extremely low dark current drift of 1.20×10⁻⁹ nA mm⁻¹ s⁻¹ V⁻¹. This stability ensures consistent response signals, a critical requirement for long-term operation.
• High Sensitivity & Detection Efficiency: The Pb₂​CuGly₂​Cl₄​ SC detector delivers a sensitivity of 9250 μC Gy⁻¹ cm⁻²—over 21 times higher than commercial α-Se detectors (which require a much stronger electric field of 15,000 V mm⁻¹). Its detection efficiency for 50 keV X-rays reaches 145%, outperforming the Br-based counterpart (∼124%).

Key Design, Synthesis, and Performance Details

1. Crystal Structure & Synthesis

The team synthesized high-quality Pb₂​CuGly₂​X₄​ SCs via a simple water evaporation method:

• Precursor solutions (containing PbX₂​, CuX₂​, and glycine) were stirred at 100 °C, then rapidly evaporated to form seed crystals.
• Slow evaporation of supersaturated solutions (50 °C for 14 days) yielded large-sized SCs: Pb₂​CuGly₂​Br₄​ (dark blue, ~4 mm × 3 mm × 1.2 mm) and Pb₂​CuGly₂​Cl₄​ (light blue, ~3 mm × 2 mm × 0.7 mm).
• XRD analysis confirmed the crystals’ high crystallinity, with the Cl-based SC showing smaller lattice constants and lower microstrain (0.02 vs. 0.07 for the Br-based SC)—indicating fewer defects and better structural quality.

2. Optoelectronic Advantages

Density functional theory (DFT) calculations and experimental characterizations revealed additional strengths:

• Both SCs are direct semiconductors (band gaps: 3.12 eV for Cl, 2.94 eV for Br) with a broad absorption range (visible to near-infrared), enabled by

• transitions of Cu²⁺.
• The Pb₂​CuGly₂​Cl₄​ SC has a higher resistivity (2.18×10¹² Ω cm) and lower trap density (2.1×10¹⁰ cm⁻³) than its Br-based counterpart. These properties reduce noise and enhance charge collection, as reflected in its higher carrier mobility-lifetime product (μτ=3.65×10⁻⁴ cm² V⁻¹).

3. Toward Practical Imaging: TFT Array Detector

To enable real-world X-ray imaging, the team developed a scalable thin-film transistor (TFT) array detector:

• Pb₂​CuGly₂​Cl₄​ nanocrystals were dispersed in water to form a paste, which was blade-coated onto a 64×64 pixel TFT array (200×200 μm² per pixel) and annealed at 100 °C.
• The resulting detector achieved a spatial resolution of 2.2 lp mm⁻¹—sufficient to clearly image the internal circuits of a network cable plug. While its sensitivity (4490 μC Gy⁻¹ cm⁻² at 100 V mm⁻¹) is lower than the SC-based detector (due to film defects), it demonstrates the feasibility of low-cost, large-area imaging devices.

Future Outlook & Significance

This work addresses a core challenge in perovskite-based X-ray detection: balancing sensitivity with stability. The amino acid ligand-metal cross-linking strategy not only expands the library of 3D perovskitoid materials but also provides a general design principle for suppressing ion migration in ionic semiconductors.

Looking ahead, the team aims to optimize the quality of Pb₂​CuGly₂​Cl₄​ thin films to further boost the TFT array detector’s sensitivity. Additionally, exploring other metal-amino acid combinations could unlock even higher-performance materials for next-generation X-ray imaging systems—from medical radiography to industrial non-destructive testing.

Stay tuned for more innovations from this collaborative team, as they continue to bridge materials design and practical detection applications!