Purely organic 4HCB single crystals exhibiting high hole mobility for direct detection of ultralow-dose X-radiation
Precise detection of low-dose X-radiation using purely organic direct detectors is vital for tissue-equivalent dosimeters and safety control in medical radiation treatment, but it still remains a challenge. Here, we report a promising organic radiation detector based on 4-hydroxycyanobenzene (4HCB, C7H5NO) single crystals. Plate-like 4HCB single crystals up to 18 × 15 × 1.2 mm3 in size are obtained by an optimized solvent evaporation method, thanks to the clarification of the two-dimensional nucleation growth mechanism. After post surface treatment, the leakage current of the 4HCB detector is no larger than 0.1 pA under an electric field of 600 V cm−1. The fabricated detectors show a capability of detecting 241Am 5.49 MeV α particles with a well resolved full energy peak. The calculated hole mobility (μh) and hole mobility lifetime product (μτ)h are 3.40 cm2 V−1 s−1 and 8.50 × 10−5 cm2 V−1, respectively. Simultaneously, under a 50 kVp X-ray beam, a detection limit as low as 0.29 μGyair s−1 with a high sensitivity of 10 μC Gyair−1 cm−2 is achieved in the bias range of 40–100 V, contributing to a superior X-ray imaging capability with a spatial resolution of 0.9 lp mm−1 at a low-dose rate (below 150 μGyair s−1) of exposure.
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