Speaker
Description
Halide perovskite semiconductors for direct X- and gamma-ray detection have currently attracted enormous attentions due to the bright prospects in various scenarios, such as medical imaging and nuclear nonproliferation in homeland security and high energy physics. Halide perovskites featuring excellent charge transport properties, low cost in preparation, and versatile processing method may offer a competitive opportunity compared to the conventional room-temperature semiconductors. As previously evidenced, the hole carriers in perovskite semiconductors have superior transport properties than electrons carriers. The unipolar sensing strategy could eliminate the such challenge induced by the electron trapping issue. However, the development of unipolar detectors for perovskite semiconductors is still at an early stage where substantial efforts are requested upon the device optimization. Here, our progresses on the perovskite CsPbBr3 detectors were reported with the configuration of pixelated and virtual Frisch grid type aiming at their deployment for the high energy resolution gamma-ray spectroscopy, ~1%@662 keV. The thickness of single-crystal detectors varied from ~3 to 20 mm which were grown by melt method. The unipolar design as indicated adequately restrained signal induction region of the hole carrier, which in turn eliminated the depth of interaction dependency between the signal amplitude partially. The carrier transport and collection dynamic was simulated in consideration of the radiation-matter interaction, charge transport and signal induction. The relationship of the carrier drift time and the signal amplitude in various detector configuration were analyzed to estimate the charge transport properties of hole carrier. The energy resolution was determined based on the signal amplitude analysis. The issues in achieving high energy resolution by unipolar perovskite semiconductors were also analyzed. Furthermore, we also demonstrated that balances charge transport for both electron and hole carriers can also be achievable through zone refining processing facilitating impurity segregation to achieve a high purity level of ~6N. Notably, a champion energy resolution of 1.3% with an outstanding photopeak-to-Compton ratio of ~5.3 was attained in an ambipolar planar detector. Such improved strategy also enables the superior reproducibility and uniformity for spectroscopic-grade CsPbBr3 crystals. We anticipate that this work shall expedite scalable manufacturing and practical applications of CsPbBr3 detectors.
