Side-chain engineering of organic semiconductor single crystal for high-resolution low-dose X-ray imaging

Organic semiconductor single crystals are considered promising materials for X-ray detection due to their tissue equivalence and low fabrication cost. However, due to the inherently weak intermolecular interactions of organic semiconductor single crystals, they generally exhibit relatively low carrier mobility, which limits the further improvement of their X-ray detection performance. Here, we obtain centimeter-sized anthracene-based 9,10-diphenylanthracene (9,10-DPA) organic semiconductor single crystals via a side-chain engineering strategy to enhance the carrier mobility of anthracene. Compared with anthracene crystals, the π-π interaction between the phenyl side groups and the anthracene backbone of 9,10-DPA crystals achieves an electron mobility of 6.83 cm² V⁻¹ s⁻¹ and an α particle energy resolution of 33.06%. The enhanced carrier transport and collection properties endow the 9,10-DPA detectors with improved detection capabilities. Meanwhile, under low X-ray dose rates, hole trapping by defects induces the injection of additional free electrons, thus realizing photocurrent amplification with a maximum gain of 2000%. Therefore, the 9,10-DPA detector exhibits outstanding comprehensive X-ray detection performance, with sensitivity as high as 1246 μC Gy_air⁻¹ cm⁻² and detection limit as low as 8.74 nGy_air s⁻¹. Consequently, the detectors can realize high-resolution X-ray imaging with a spatial resolution of 4.8 lp mm⁻¹ at a relatively lower dose rate (0.67 μGy_air s⁻¹). This work provides crucial support for the development of organic detectors in low-dose medical X-ray imaging.