Pure organic TPB single crystal for direct X-ray detection

• Published in: CrystEngComm 2024-04, Vol.26 (17), p.2241-2247
• Main Authors: Jiang, Kai, Xu, Lingyan, Shang, Rongjin, Liang, Lu, Wang, Yingming, Qin, Zhentao, Jie, Wanqi
• Format: Article
• Language: English
• Subjects: Alpha particles; Alpha rays; Crystal growth; Electrons; Energy resolution; Gamma rays; Mathematical analysis; Nucleation; Organic compounds; Scintillation counters; Single crystals; Spectral sensitivity
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/d4ce00200h

For a long time, single crystals of the organic compound TPB (1,3,5-triphenylbenzene) have been viewed as a scintillator material for indirect X-ray detection. We here attempt to explore their potential for direct detection. A TPB single crystal with a size of up to 20 × 6 × 4 mm 3 and without obvious growth steps was obtained using a solvent volatilization method. It has an orthorhombic structure with a high-quality FWHM of as low as 0.059 and preferred grown orientations along (131) and (220). AFM images clarify the two-dimensional nucleation growth mechanism. The fitted bandgap of the as-grown crystal is about 3.65 eV. TPB detectors with vertical and coplanar electrodes with a resistivity of 2.56 × 10 13 Ω cm and 6.68 × 10 13 Ω cm, respectively, were prepared. The mobilities for electrons ( μ e ) and holes ( μ h ) for the coplanar device were calculated to be 1.12 cm 2 V −1 s −1 and 1.02 cm 2 V −1 s −1 , respectively. Under a 50 kV X-ray beam, the detection limit is as low as 0.35 μGy s −1 , and the sensitivity reaches 2.72 μC Gy −1 cm −2 . The TPB devices have the ability to detect 241 Am@5.49 MeV α particles, showing the full-energy peak collected from the holes with an energy resolution of 39.13% at 700 V. The mobility lifetime product of the TPB devices for electrons ( μτ ) e and holes ( μτ ) h were calculated to be up to 2.24 × 10 −5 cm 2 V −1 and 4.04 × 10 −5 cm 2 V −1 , respectively. The TPB detector could present a spectral response to 241 Am@59.5 keV γ-rays from the holes with an energy resolution of 44.25% at 1000 V, which shows the potential for both direct and indirect detection of high-energy radiation. High-quality TPB single crystals were obtained without obvious step-like growth morphology. The TPB devices could present α-particle and γ-ray spectral responses with high energy resolution, showing potential for direct radiation detection.