17 research outputs found
Molecular weight tuning of organic semiconductors for curved organicâinorganic hybrid Xâray detectors
Curved X-ray detectors have the potential to revolutionize diverse sectors due to benefits such as reduced image distortion and vignetting compared to their planar counterparts. While the use of inorganic semiconductors for curved detectors are restricted by their brittle nature, organicâinorganic hybrid semiconductors which incorporated bismuth oxide nanoparticles in an organic bulk heterojunction consisting of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) are considered to be more promising in this regard. However, the influence of the P3HT molecular weight on the mechanical stability of curved, thick X-ray detectors remains less well understood. Herein, high P3HT molecular weights (>40 kDa) are identified to allow increased intermolecular bonding and chain entanglements, resulting in X-ray detectors that can be curved to a radius as low as 1.3 mm with low deviation in X-ray response under 100 repeated bending cycles while maintaining an industry-standard dark current of <1 pA mmâ2 and a sensitivity of â 0.17 ÎŒC Gyâ1 cmâ2. This study identifies a crucial missing link in the development of curved detectors, namely the importance of the molecular weight of the polymer semiconductors used
Ultraâlow dark current organicâinorganic hybrid Xâray detectors
Organicâinorganic hybrid semiconductors are an emerging class of materials for direct conversion Xâray detection due to attractive characteristics such as high sensitivity and the potential to form conformal detectors. However, existing hybrid semiconductor Xâray detectors display dark currents that are 1000â10 000Ă higher than industrially relevant values of 1â10 pA mmâ2. Herein, ultraâlow dark currents of <10 pA mmâ2, under electric fields as high as â4 V ”mâ1, for hybrid Xâray detectors consisting of bismuth oxide nanoparticles (for enhanced Xâray attenuation) incorporated into an organic bulk heterojunction consisting of pâtype Poly(3âhexylthiopheneâ2,5âdiyl) (P3HT) and nâtype [6,6]âPhenyl C71 butyric acid methyl ester (PC70BM) are reported. Such ultraâlow dark currents are realized through the enrichment of the hole selective pâtype organic semiconductor near the anode contact. The resulting detectors demonstrate broadband Xâray response including an exceptionally high sensitivity of â1.5 mC Gyâ1 cmâ2 and <6% variation in angular dependence response under 6 MV hard Xârays. 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