Ultra-low voltage driven high-resolution perovskite gamma spectroscopy detector

Radiation detectors are widely used in important fields such as medical imaging, safety inspection, deep space exploration and security and national defense, and can be divided into indirect detectors based on scintillators and direct detectors based on optosemiconductors according to the working principle of the device. Direct detection technology has higher energy conversion efficiency and significantly improved energy resolution, and is a new generation of radiation detection technology with great application prospects. The basis of direct detection technology is high-quality detection-grade semiconductor single crystals. In recent years, metal halide perovskite materials have made great progress in the field of radiation detection, and pure inorganic perovskite single crystals grown by high-temperature melting method have approached commercial zinc-cadmium tellurium (CZT) materials in terms of energy-resolved detector performance, showing great application potential of perovskite materials. However, the experimental and inorganic hybrid perovskite crystals prepared by the solution method with a simpler and cheaper preparation process still have a big gap in radiation detection performance and the properties of commercial CZT materials, mainly because it is still challenging to grow low defect density, large size and high uniformity crystals by solution method. At the same time, to achieve energy spectrum detection, efficient single-photon charge conversion and collection are required, which requires extremely high crystal quality and comprehensive performance of devices, and the current commercial high-performance ray spectrum detectors still need a high driving voltage of nearly 1,000 volts to obtain better energy spectral performance, which also limits its application range.

Recently, a joint research team composed of Professor Dong Qingfeng’s research group of Jilin University, researcher Fang Yanjun of Academician Yang Deren’s team of Zhejiang University, and Li Liansheng, senior engineer of Beijing Institute of Control Engineering, realized the stress regulation of perovskite crystal growth process by constructing a fluorine-containing soft gel (F-gel) interface between the crystal and substrate, and grew a high-quality, high-quality, domain-scale uniformity through the inverse temperature confinement method of the solution process. Wafer-sized detection grade CH3NH3PbI3 (MAPbI3) perovskite single wafers, and ultra-low voltage driven high-resolution gamma ray spectroscopy detectors were prepared.

Figure 1. Gel base growth crystals

Compared with the traditional hard contact, the crystal-substrate soft contact interface constructed by F-gel can eliminate the lattice mismatch between the crystal and the substrate, alleviate the physical obstacles caused by the hard substrate during the growth of crystals by the space-confined method, and reduce the crystal defect density. In addition, the low surface energy of perfluorinated molecular chains can inhibit interfacial chemical interactions and eliminate stress between crystals and substrates, thereby providing a growth environment close to open systems, favoring large-size and high-quality crystal growth. (Figure 1)

Figure 2. Near-infrared polarizing light microscopy probes the internal structure of the crystal

In addition, the authors developed a method to observe internal defects and domains of crystals using an infrared polarized light imaging system. As shown in Figure 2, crystals grown on the F-gel substrate have highly uniformly arranged domains, higher crystallinity and lower crystal defect density, which provides a material basis for the realization of high-performance radiation detectors.

Figure 3. Perovskite single crystal radiation detector performance

Figure 3a shows a schematic diagram of a radiation detector device prepared from the above high-quality crystals. The device prepared from this crystal exhibits excellent stability, and the photocurrent remains consistent with the initial state after 7 months of storage in air (Figure 3b); In addition, the device exhibits a low dark current and a stable dark current baseline at a high electric field of 1000 V cm-1, which greatly improves the signal-to-noise ratio of the device under irradiation and results in a more stable output signal (Figure 3c). The authors compared the sensitivity and dark current drift properties of radiation detectors prepared by various perovskite materials that have been reported so far, and found that the three-dimensional perovskite single crystal prepared based on this method has high sensitivity (3×105 μC Gy-1air cm-2) while maintaining the low current drift properties similar to low-dimensional perovskite single crystal (Figure 3d), which provides the possibility of single-photon energy resolution. Finally, under the ultra-low operating voltage driving condition of 5 V, an energy resolution of 4.9% was obtained under the standard gamma source of 241Am, which is the optimal value of the radiation detector prepared by the solution method in the same energy range, and its energy resolution is also very close to the level of commercial CZT detectors driven by high voltage of thousands of volts (Figure 3e-f).

The growth of perovskite crystals by solution method can greatly reduce the preparation cost of detection grade crystals. At the same time, the ultra-low working voltage driven γ ray spectroscopy detection technology provides a new ray spectroscopy detection path, which is of great significance for future medical imaging and industrial radiation detection applications. In addition, the solution growth method proposed by the soft contact gel substrate provides a promising strategy for the direct preparation of large-size perovskite single wafers, which is also helpful for the development of other optoelectronic devices based on perovskite single crystals, such as solar cells, light-emitting diodes and photodetectors.

The result is titled “Detector-Grade Perovskite Single Crystal Wafers via Stress-· Free Gel-Confined Solution Growth Targeting High-Resolution Ionizing Radiation Detection” was published in Light: Science & Applications. (Source: LightScience Applications WeChat public account)

Related paper information:‍-023-0‍1129-y

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