Text-Embedding-Assisted Design of Rigid Molecular Cations for Suppressing Ion Migration in Hybrid Single-Crystal X-ray Detectors.
Authors
Affiliations (7)
Affiliations (7)
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education; Shaanxi Key Laboratory for Advanced Energy Devices; Shaanxi Engineering Lab for Advanced Energy Technology; International Joint Research Center of Shaanxi Province for Photoelectric Materials Science; Institute for Advanced Energy Materials; School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, China.
- Key Laboratory of Photoelectric Conversion and Utilization of Solar Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, Liaoning, China.
- Shanghai Artificial Intelligence Laboratory, Shanghai 200032, China.
- Semiconductor Research Center, Hon Hai Research Institute, Taipei 114, China.
- School of Materials Science and Engineering, Xi'an University of Science and Technology, Xi'an 710054, China.
- Hong Kong Institute of AI for Science (HKAI-Sci), City University of Hong Kong, Hong Kong 999077, SAR, China.
- Department of Materials Science and Engineering, Hong Kong Institute for Clean Energy, City University of Hong Kong, Hong Kong 999077, SAR, China.
Abstract
Hybrid single crystals exhibit remarkable optoelectronic properties that make them highly promising for photovoltaic devices and radiation detectors. However, ion migration-induced instability represents a critical barrier to their commercial viability. By integrating large language models (LLMs) with k-Nearest Neighbor (kNN) algorithms, we develop a machine-learning model that identifies rigid organic cations as effective modulators for perovskite crystal stiffness, thereby suppressing ion migration. Guided by the analysis, we replaced the flexible alkyl chains in (HDA)BiI<sub>5</sub> (HDA = 1,6-hexanediamine) with rigid carbon rings to synthesize a highly stable (CHDA)BiI<sub>5</sub> single crystal (CHDA = trans-1,4-diaminocyclohexane). Density functional theory (DFT) calculations revealed that the rigid CHDA molecule exhibits ordered vibrations and stronger interactions with the inorganic framework compared to the disordered vibrations of HDA. Solid-state nuclear magnetic resonance (SSNMR) spin-lattice relaxation measurements further confirmed enhanced lattice rigidity, with the relaxation rate decreasing from 1.29 s<sup>-1</sup> to 0.15 s<sup>-1</sup>, enhancing lattice rigidity. Consequently, the ion migration activation energy increased substantially from 0.42 to 0.61 eV. The resulting (CHDA)BiI<sub>5</sub> X-ray detector achieved an exceptional sensitivity of 8209 μC·Gy<sub>air</sub><sup>-1</sup>·cm<sup>-2</sup> at 175 V/mm and a low detection limit of 4.7 nGy s<sup>-1</sup>. This study underscores the pivotal role of organic cation rigidity in optimizing the structural stability and functional performance of low-dimensional hybrid semiconductors.