Ultra-Low Dark Current Organic–Inorganic Hybrid X-Ray Detectors

Abstract

Organic-inorganic hybrid semiconductors are an emerging class of materials for direct conversion X-ray detection due to attractive characteristics such as high sensitivity and the potential to form conformal detectors. However, existing hybrid semiconductor X-ray detectors display dark currents that are 1000–10 000× higher than industrially relevant values of 1–10 pA mm−2. Herein, ultra-low dark currents of <10 pA mm−2, under electric fields as high as ≈4 V µm−1, for hybrid X-ray detectors consisting of bismuth oxide nanoparticles (for enhanced X-ray attenuation) incorporated into an organic bulk heterojunction consisting of p-type Poly(3-hexylthiophene-2,5-diyl) (P3HT) and n-type [6,6]-Phenyl C71 butyric acid methyl ester (PC70BM) are reported. Such ultra-low dark currents are realized through the enrichment of the hole selective p-type organic semiconductor near the anode contact. The resulting detectors demonstrate broadband X-ray response including an exceptionally high sensitivity of ≈1.5 mC Gy−1 cm−2 and <6% variation in angular dependence response under 6 MV hard X-rays. The above characteristics in combination with excellent dose linearity, dose rate linearity, and reproducibility over a broad energy range enable these detectors to be developed for medical and industrial applications.