A research team led by Dong Qingfeng from Jilin University and Fang Yanjun from Zhejiang University published a research paper titled "In-line tempering eliminates the domain boundary in perovskite single crystals for high–energy resolution ionizing radiation detectors" in the journal Science Advances. Xueying Yang is the first author, and Dong Qingfeng and Fang Yanjun are co-corresponding authors.
Key Highlight: This paper proposes an online tempering strategy at the critical phase transition temperature to alleviate microstrain and homogenize the domain orientation of methylammonium lead iodide (MAPbI3) perovskite SCs. A gamma-ray spectrometer detector utilizing these strain-relaxed SCs achieved an energy resolution of 7.2% at 59.5 keV using a 241Am gamma-ray source, and a 25-pixel device exhibited high uniformity under concentrated current distribution.

In recent years, metal halide perovskite single crystals (SCs) have emerged as promising candidates for ionizing radiation detection. During crystal growth, physical hindrance from the hard substrate and stress induced by the lattice mismatch between the SC and the substrate also contribute to the formation of randomly oriented ferroelastic domains. These double-domain boundaries negatively impact carrier recombination under solar cell operating conditions. This effect is particularly pronounced in low-flux pulsed-mode radiation detection, where the gamma photon flux is very low. Furthermore, due to the randomly oriented domains in SCs, the fabrication of high-performance radiation detectors remains crucially dependent on careful crystal selection. This is due to significant residual stress, which significantly limits the yield of detector-grade perovskite SC wafers.
Based on this, the research team led by Qingfeng Dong of Jilin University and Yanjun Fang of Zhejiang University proposed an online annealing strategy to alleviate microstrain and homogenize domain orientation in methylammonium lead iodide (MAPbI3) perovskite SCs. By removing ferroelastic domain walls, the gradual strain release during the in-situ phase transition significantly improves the crystallinity and optoelectronic properties of MAPbI3 SCs. As a result, gamma-ray spectrometers utilizing these strain-relaxed SCs achieved an energy resolution of 7.2% at 59.5 keV from a 241Am gamma-ray source. The 25-pixel device exhibited highly uniform current distribution under concentrated current distribution. Furthermore, even with a simple packaging scheme, they displayed consistent and stable photon responses for over six months under ambient conditions.
This study employed a temperature gradient to reorient domains in MAPbI3 SCs. The resulting crystals exhibited single orientation and no domain walls, demonstrating excellent optoelectronic properties with reduced trap density, enhanced carrier transport, and improved sensitivity. Spatial uniformity was significantly improved in the context of large-area SCs, and in-line annealing treatment resulted in a more stable response and a more concentrated current distribution. These findings highlight the significant potential of SCs for scalable fabrication and their potential for low-cost, high-performance, and stable photon counting imaging applications. This paves the way for their implementation in high-resolution radiation spectroscopy.