X‐ray Detectors With Ultrahigh Sensitivity Employing High Performance Transistors Based on a Fully Organic Small Molecule Semiconductor/Polymer Blend Active Layer

The implementation of organic semiconductor (OSC) materials in X-ray detectors provides exciting new opportunities for developing a new generation of biocompatible devices with high potential for the fabrication of sensitive and low-cost X-ray imaging systems. Here, the fabrication of high performance organic field-effect transistors (OFETs) based on blends of 1,4,8,11-tetramethyl-6,13-triethylsilylethynyl pentacene (TMTES) with polystyrene is reported. The films are printed employing a low cost and high-throughput deposition technique. The devices exhibit excellent electrical characteristics with a high mobility and low density of hole traps, which is ascribed to the favorable herringbone packing (different from most pentacene derivatives) and the vertical phase separation in the blend films. As a consequence, an exceptional high sensitivity of (4.10 ± 0.05) × 1010 µCGy–1cm–3 for X-ray detection is achieved, which is the highest reported so far for a direct X-ray detector based on a tissue equivalent full organic active layer, and is higher than most perovskite film-based X-ray detectors. As a proof of concept to demonstrate the high potential of these devices, an X-ray image with sub-millimeter pixel size is recorded employing a 4-pixel array. This work highlights the potential exploitation of high performance OFETs for future innovative large-area and highly sensitive X-ray detectors for medical dosimetry and diagnostic applications.
This work was funded by the Spanish Government within: research projects GENESIS PID2019-111682RB-I00 and RTI2018-095460-B-I00, the “Severo Ochoa” Programme for Centers of Excellence in R&D (FUNFUTURE CEX2019-000917-S) and the “María de Maeztu” program for Spanish Structures of Excellence (MDM-2017-0767). Funding was also provided by the Generalitat de Catalunya (2017-SGR-918, 2017-SGR13). A.T. acknowledges his FPU fellowship and is enrolled in the UAB Materials Science PhD program. C.M-D. acknowledges her Juan de la Cierva grant (ref. FJC2019-042161-I) from Ministerio de Ciencia e Innovación. I.F., A.C., B.F. and L.B. acknowledge funding from INFN through the CSN5 FIRE project. All the authors acknowledge Giuliana Tromba and Diego Dreossi at ELETTRA synchrotron in Trieste for hardware and software technical support during the experiments, in particular for the acquisition of X-ray image. R.S. acknowledges funding from MINECO under grant agreement CTQ2017-87773-P/AEI/FEDER.
With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).