Moreover, the emission intensity of BTD-HeBr remains > 96% under repeated X-ray excitation for 50 min (57 on-off circles), highlighting its good photostability. In addition, the average luminescence decay time of BTD-HeBr (excited using an X-ray pulse) is fitted as 3.43 ns (Supplementary Fig. ), which is consistent with the PL decay time (3.74 ns). Furthermore, the RL intensity of BTD-HeBr was linear response to the X-ray dose rate in the range 0.401-570.1 μGy s -1 (Fig. ). Additionally, the detection limit is a measure of the response linearity at low excitation levels and can be defined as the dose rate at which the signal-to-noise ratio (SNR) equals 3. The detection limit was 84.6 nGy s -1 for BTD-HeBr films, which is significantly below the minimum X-ray dose rate requirement for medical X-ray imaging (5.5 μGy s -1 ) , demonstrating the highly potential of medical radiography applications. Fig. | RL performance characterizations of the HLCT scintillators. a, X-ray absorption spectra of BTD-FL, BTD-FLBr, and BTD-HeBr emitters measured as a function of X-ray energy . b, Images of these HLCT emitters taken under X-ray irradiation (X-ray tube voltage, 50 kV; dose rate, 2.023 mGy s -1 ). c, RL spectra of these HLCT emitters with an optimal thickness (X-ray tube voltage, 50 kV; dose rate, 2.023 mGy s -1 ). d, The RL emission photostability for the BTD-HeBr versus continuous irradiation (top) and repeated on-off cycles of X-rays (bottom) at a dose rate of 2.023 To achieve high performance and good processability of the HLCT scintillation films for X-ray imaging, glassy neat films are fabricated by melting the HLCT emitters at a relatively low temperature of 120°C for X-ray correlated measurements due to their low glass transition temperatures (Supplementary Fig. ). The thickness-dependent RL of BTD-HeBr shows significantly high intensity with an optimal thickness at 180 μm (Supplementary Fig. ). In addition, the transmittance of the BTD-HeBr glassy film exceeds 93% within the wavelength range of 500-800 nm, encompassing the entire emission spectrum (Supplementary Fig. ). This feature can enhance the photon collection efficiency during optical characterization and may realize high resolution for X-ray imaging. The ultra-high X-ray imaging resolution of 40.5 lp mm -1 was achieved at a modulation transfer function (MTF) of 0.2 for BTD-HeBr scintillation screen, according to the MTF calculation of standard X-ray edge images (Fig. ). As far as we know, such a high imaging resolution exceeds those of all reported organic scintillators (Fig. and Supplementary Table ), which supports the high practical potential of using through-space heavy atom-π interactions for efficient X-ray imaging scintillators in HLCT emitters. To further verify this value, we took X-ray images of a standard X-ray test pattern plate. A bright-field photograph was shown in Supplementary Fig. , and the X-ray image (Fig. ) demonstrates that the line pair notches at 33.3 lp mm -1 were clearly detectable and the line pair notches at 50.0 lp mm -1 were roughly detectable. Furthermore, we performed imaging tests using BTD-HeBr scintillators to demonstrate their practical value. Spring-loaded pens, positioned between an X-ray source and a BTD-HeBr film (Figure ), allowed the otherwise invisible springs to be distinctly captured on the film, with the plastic casing appearing almost transparent. Furthermore, X-ray contrast imaging facilitated the examination of the intricate internal structure of an electronic chip, which is typically impenetrable to the naked eye (Figure ). The intricate architecture of the electronic chip was vividly revealed using a BTD-HeBr scintillating screen. These results demonstrate the promising potential of the HLCT scintillators with through-space heavy atom-π interactions in medical radiography. and an electronic chip (e) before and after X-ray exposure (dose rate, 2.023 mGy s -1 ).