Dimensionality-tailored pure organic semiconductor with high hole mobility for low-dose x-ray imaging

Pure-organic semiconductors have attracted broad interest in tissue-equivalent and biocompatible X-ray sensors, while their low-dose X-ray imaging capability still suffers from poor charge transport properties. Here, we report a dimensionality tailoring method to enhance hole transport in pure-organic semiconductors, enabling highly stable and low-dose X-ray detection and imaging without toxic elements such as Pb or Hg. By substituting the -CN group in 4-hydroxycyanobenzene (4HCB, HO-C₆H₄-CN) with a -COOCH₃ group, we transform the two-dimensional (2D) structure into a three-dimensional (3D) 4-methyl hydroxybenzoate (4MHB, HO-C₆H₄-COOCH₃) crystal featuring enhanced intermolecular π-π stacking. This structural reconfiguration yields a high hole mobility of 19.91 cm² V^-1 s^-1 and an ultralow dark current drift of 1.14 × 10^-10 nA cm^-1 s^-1 V^-1 at 100 V mm^-1. The superior charge transport facilitated by stronger π-π interactions enables stable X-ray detection with a detection limit as low as 4.22 nGy_air s^-1 and high-resolution imaging at 1.6 lp mm^-1 under low-dose irradiation (58.76 μGy_air s^-1). This work demonstrates a molecular tailoring strategy to modulate the structural dimensionality and the charge transport path of pure-organic semiconductors, advancing tissue-equivalence and biocompatible X-ray imagers toward high-resolution and low-dose operation.