卤化铅钙钛矿单晶异质结以其独特的高灵敏度、高分辨率、高稳定性和低检出限的特点，在X射线探测中受到了广泛关注。然而，这些钙钛矿异质结中Pb的毒性限制了它们的实际应用。
近日，山东大学张国栋教授等人在Science China Materials发表研究论文，采用降温结晶法构建了第一个面积为20 × 20 mm2的全无机无铅Cs2AgBiBr6/Cs3Bi2Br9单晶异质结。
本文要点
1) 3D Cs2AgBiBr6单晶薄膜在2D Cs3Bi2Br9单晶衬底上的外延结晶需要更大的驱动力，因此通过大的冷却速率使其生长模式从Volmer-Weber过渡到逐层生长。2) Cs2AgBiBr6/Cs3Bi2Br9单晶异质结探测器在100 keV硬X射线探测下，室温下灵敏度高达1390 μC Gyair−1 cm−2，75°C下增加到2075 μC Gyair−1 cm−2，且高温稳定性优异。此外，该探测器具有37.48 nGyair s−1的低检测限和长达90天的优异稳定性。Figure 1. (a) Schematic apparatus for the epitaxial growth of CABB SC films on CBB substrates. (b) Illustration of the lattice match between the CABB (111) and CBB (001) crystallographic planes. (c) Temperature-dependent solubility curve of CABB in HBr solution. Photographs of (d) CABB SC, (e) CBB substrate, and (f) CABB/CBB heterostructure SC.Figure 2. (a) SEM image of CABB crystals with a slow cooling rate of 0.067 °C h−1. SEM images of CABB nucleation at (b) 50 °C and (c) 42 °C on the CBB substrate with a rapid cooling rate of 9 °C h−1. (d) Surface-energy values plotted for each surface: CBB (001) and CABB (111). (e) Contact angle measurement of diiodomethane (top) and glycerol (bottom) on CBB (001) and CABB (111). (f) Gibbs free energy variation on the CBB (001) and CABB (111) surfaces. (g) Schematic diagram of the heteroepitaxial nucleation process on the CBB (001).![]()
Figure 3. (a) Energy-band schematic diagram of the heterojunction device. (b) Surface potential mapping of the interface of the CABB/CBB heterojunction. (c) I-V curve of the heterojunction device measured in the dark. (d) Bias-dependent photoconductivity of the devices based on the heterojunction and CABB SC. (e) Normalized TRMC decays of the heterojunction and CABB SC. (f) Comparison of dark-current drifts for the heterojunction and CABB SC at 660 V mm−1. Temperature-dependent ionic conductivity measurements of (g) CABB SC, (h) CBB SC, and (i) heterojunction SC.![]()
Figure 4. (a) Structure of the SC heterojunction X-ray detector. (b) Time-dependent X-ray responses of the heterojunction detector under the electric field of 660 V cm−1 for 100 keV. (c) Dose-rate-dependent current density of heterojunction X-ray detectors under different electric fields. (d) Sensitivities of the heterojunction detector for 40- and 100-keV X-rays under different electric fields. (e) Dose-rate-dependent X-ray current density of the heterojunction detector at different temperatures. (f) Time-dependent current response and (g) dose-rate-dependent SNR of heterojunction detectors. (h) Comparison of X-ray detection performance of some lead-free perovskite detectors. (i) X-ray response stability of the CABB/CBB heterojunction detectors at room temperature.Hongjie Liu, Xue Sun, Jiaxin Liu, Xiang Li, Yunqiu Hua, Zhongjie Yue, Jian Song, Xilong Wang, Yujie Yang, Qianqian Lin, Zhongjun Zhai, Xutang Tao, Guodong Zhang. Lead-free perovskite Cs2AgBiBr6/Cs3Bi2Br9 single-crystalline heterojunction X-ray detector with enhanced sensitivity and ultra-low detection limit. Sci. China Mater. (2024).https://doi.org/10.1007/s40843-024-3159-8
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