7 October 2014 Fabrication of an x-ray detector based on molecular plastic electronics
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We present an organic X-ray detector with an active layer deposited from a novel semiconducting ink formulation. The precursor ink consists of blended poly(3-hexylthiophene-2,5-diyl) (P3HT), phenyl-C61-butyric acid methyl ester (PCBM) and the organometallic nanostructure copper(II) 2,2'-bipyridine (Cu(II)BPY). The use of ligands like 2,2' byripidine with cationic species such as Cu(II) improves their solubility in organic solvents. The purpose of the organometallic complex Cu(II)BPY is twofold: to achieve a homogeneous semiconducting ink with P3HT:PCBM blends and to enhance the X-ray interaction with the organic layer through the Cu(II) cation. Our X-ray displays consist of several pixels, each with vertical structures comprising a bendable PET/ITO substrate with a spin-coated semiconducting ink of P3HT:PCBM:Cu(II)BPY (60 nm), followed by thermal evaporation of Al (100 nm) contacts. To the best of our knowledge, this is the first example where an organic X-ray detector includes the organometallic complex Cu(II)BPY in P3HT:PCBM blends, and the electrical characterization of the detector is carried out by impedance spectroscopy (IS). In order to test the devices, each pixel is exposed to X-ray energies ranging from 0 keV to 35 keV and characterized by impedance spectroscopy (IS). Impedance spectra were recorded at frequencies between 20 Hz and 20 kHz and at a modulating signal of 50 mV. Analysis of IS measurements revealed a linear dependence between impedance and X-ray energy. IS analysis is more sensitive compared with standard photocurrent-voltage characteristics.
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Beynor A. Paez-Sierra, Beynor A. Paez-Sierra, Hernán Rodríguez, Hernán Rodríguez, Juan M. Sánchez, Juan M. Sánchez, Miguel A. Rodríguez, Miguel A. Rodríguez, Leon D. Pérez, Leon D. Pérez, } "Fabrication of an x-ray detector based on molecular plastic electronics", Proc. SPIE 9185, Organic Field-Effect Transistors XIII; and Organic Semiconductors in Sensors and Bioelectronics VII, 91851P (7 October 2014); doi: 10.1117/12.2062261; https://doi.org/10.1117/12.2062261


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