【Adv.Mater.】江西师范大学罗军华等|灵敏度达9645.2！超窄间距3.09 Å极性无铅钙钛矿解锁自驱动X射线探测新纪录
文章标题：Ultranarrow‐Spaced Polar Green Aromatic Dion–Jacobson Hybrid Perovskite Enables Highly Sensitive and Stable Self‐Powered X‐Ray Detection
通讯作者：Panpan Yu, Zeng-Kui Zhu, Junhua Luo
Inserting a 4AMPY aromatic organic diamine cation into 3D centrosymmetric HP Cs2AgBiBr6 to construct 2D polar green aromatic DJ-type HP (4AMPY)2AgBiBr8.
文章概要
引言
极性晶体材料由于内部正负电荷中心不重合，能产生自发极化并形成内置电场。在光照或射线辐射下，这种内置电场可直接驱动光生载流子发生定向分离，从而实现无需外加偏压的自驱动光伏效应。这种特性在低功耗、低噪声的X射线探测领域具有巨大的应用潜力。然而，传统的极性材料往往面临制备工艺复杂、晶体生长困难且成本高昂等挑战。近年来，二维狄翁-杰各布森（DJ）型杂化钙钛矿因其层间距短、能有效抑制离子迁移而成为研究热点。但在以往研究中，多数DJ型钙钛矿仍依赖有毒的铅元素，且采用的脂肪族胺具有较低的介电常数，限制了电荷传输效率。开发新型、环境友好且兼具高稳定性的极性芳香族DJ型无铅钙钛矿探测材料，一直是该领域亟待突破的瓶颈。
(a) High-quality large crystal photo of 1. (b) Analysis diagram of strong hydrogen bonding forces in the structure. (c) Hirshfeld surface analyses of the 4AMPY2+ cations, and the light red dots represent N-H···Br and C-H···Br hydrogen bonds. (d) The corresponding 2D fingerprint plots analyzed. (e) The interlayer distance of 1. (f) Comparison of interlayer distance and density with other double perovskites. FPEA, R-MPA, CPA, PA, DFPD, HA, BDA represent (FPEA)4AgBiBr8 [32], (R-MPA)4AgBiI8 (R-MPA = R-β-methylphenethylammonium) [38], (CPA)4AgBiBr8 (CPA = chloropropylammonium) [39], (PA)4AgBiBr8 [34], (DFPD)4AgBiI8 (DFPD = 4,4-difluoropiperidinium) [40], (HA)4AgBiBr8 [33], (BDA)4AgBiBr8 (BDA = 1, 4-butanediamine) [41].
主要实验及结论
研究人员通过在经典的三维双钙钛矿框架中引入芳香族双胺阳离子（4AMPY），成功诱导结构重构，制备出具有极性空间群的二维DJ型无铅杂化钙钛矿单晶。结构表征与理论计算表明，该晶体内部形成了极其紧密的层间氢键网络，有效消除了层间范德华间隙，使其层间距达到了极窄的3.09 Å。这种独特的芳香族阻挡层结构不仅大幅增强了晶格刚性，还赋予了材料高达8.64×10¹⁰ Ω·cm的电阻率和低至1.17×10¹⁰ cm⁻³的缺陷态密度，在晶体内部搭建了极其平滑且高效的电荷传输通道。
(a) The absorption coefficient of crystal 1 at different wavelengths and the calculated optical band gap (inset). (b) The density functional theory (DFT) calculations of 1. (c) The resistivity of 1. (d) The defect density of 1 was measured by the SCLC method. (e, f) SEM and AFM images of 1.
(a) The absorption spectra of 1, Si, α-Se, (HIS)2AgSbBr8, and (HIS)2AgBiBr8. (b) Attenuation efficiency of 50 keV X-ray photons under different thicknesses for 1, Si, α-Se, (HIS)2AgSbBr8, and (HIS)2AgBiBr8. (c) The 𝜇𝜏 product values of 1. (d) Photovoltage of device 1 measured under different X-ray irradiation doses. (e, f) The X-ray response intensity of device 1 under 0 V bias and 100 V bias. (g) The dependence of the response intensity of device 1 on dose rate under different biases. (h) The sensitivity of device 1 obtained by fitting under different biases. (i) Detection limit of device 1 under 0 V bias.
在探测性能测试中，该材料由于其固有的非中心对称结构与自发极化效应，在X射线照射下展现出显著的大块光伏效应，产生了0.68 V的内置光电压。得益于优异的载流子收集与传输效率，该单晶器件在0 V和100 V偏压下分别实现了661.4和9645.2 µC Gy⁻¹ cm⁻²的超高灵敏度，并获得了12.3 nGy s⁻¹的极低探测极限。此外，晶体内部高达0.87 eV的离子迁移活化能有效抑制了高压下的缺陷漂移，使器件在无封装状态下暴露空气三个月后，仍能保持96%以上的初始灵敏度，展现出卓越的辐射耐受性与长期储存稳定性。
(a) PXRD patterns of 1 after being left unpackaged for 1 and 3 months, respectively. (b) The initial _I_drift value of sample 1 and the value after being left unpackaged for 3 months. (c) The _I_drift values of device 1 compared with other HP materials. (d) Compare the X-ray response of device 1 with the initial value after three months. (e) Compare the detection sensitivity of device 1 with the initial value after three months. (f) Compare the detection limit of device 1 with the initial value after three months. (g) The radiation resistance stability of device 1.
总结及展望
这项研究通过精妙的材料结构设计，成功将强刚性的芳香族双胺分子嵌入无铅双钙钛矿体系中，不仅实现了晶体由中心对称向极性结构的转变，还兼顾了极高的探测效率与环境稳定性。超窄的层间距与强大的层间氢键相互作用，共同赋予了该材料在自驱动模式下打破历史纪录的探测灵敏度，以及远超商业化非晶硒材料的超低探测下限。这一成果为设计下一代环保、低功耗且高灵敏度的极性杂化钙钛矿辐射探测器提供了全新的创制思路，未来有望在临床医学影像、安全检查以及低功耗智能传感等领域发挥重要的产业应用价值。