Scintillators, the core components in X-ray detection systems, are a class of materials that can convert high-energy radiation into visible or near-visible light. Efficient scintillators require high photoluminescence yield, high energy resolution, swift response time, sensitive ionization detection, and outstanding mechanical and chemical stability.

Manganese (Mn)-based inorganic-organic hybrid metal halide scintillators with superior thermal stability, mechanical strength and processability have applications in nuclear medicine, radiation detection and industrial testing. However, there is a significant lack of research on the effects of temperature on Mn-based scintillators, especially in terms of the mechanisms of luminescence and scintillation.

In a study published in Laser & Photonics Reviews, a research group led by Prof. GUO Guocong from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences conducted a detailed study of Mn-based inorganic-organic hybrid metal halide scintillators with rare anomalous thermally excited excitons, and developed a Mn-based organic-metal halide hybrid nanoscintillator Mn-1 NCs ((mtpp)₂MnCl₄) with high luminescence efficiency which can be prepared on a large scale.

Mn-1 NCs exhibited a decrease in photoluminescence intensity with increasing temperature within the range of 77 to 150 K. This is due to the fact that the excitation electrons of Mn²⁺ ions cannot overcome the trap energy level in this temperature interval, following the Dexter energy transfer process. 

In contrast, within the temperature range of 150 to 350 K, the photoluminescence intensity of Mn-1 NCs increased with rising temperature, even surpassing the intensity observed at 77 K. This is because the increase in temperature assists the trapped charge carriers in escaping the trap layer and returning to the luminescent center of Mn²⁺ ions through an energy inversion process, partially compensating for the luminescence loss caused by the temperature increase.

The scintillation intensity of Mn-1 NCs surpasses that of the commercial scintillator Bi₄Ge₃O₁₂, with a detection limit of 1.01 μGy_air/s, which is lower than the standard diagnostic dose rate in medical imaging (5.5 μGy_air/s). 

Mn-1 NCs exhibited superior radiation resistance, solvent stability, and air stability. Flexible scintillating films based on Mn-1 NCs allow for the clear visualization of the internal structures of objects such as utility knives and headphones, achieving an imaging spatial resolution of 11.3 lp/mm.

This study elucidates the luminescence mechanism of organic-inorganic hybrid metal halide scintillating materials, opening up new avenues for the design of high-performance scintillators.