Sergi Riera-Galindo1,Raphael Pfattner1,2,Jinghai Li1,Elena Laukhina2,Rossella Zaffino1,Nuria Aliaga-Alcalde1,Marta Mas-Torrent1,2,Vladimir Laukhin1,Jaume Veciana1,2
Materials Science Institute of Barcelona (ICMAB-CSIC)1,Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN)2
Sergi Riera-Galindo1,Raphael Pfattner1,2,Jinghai Li1,Elena Laukhina2,Rossella Zaffino1,Nuria Aliaga-Alcalde1,Marta Mas-Torrent1,2,Vladimir Laukhin1,Jaume Veciana1,2
Materials Science Institute of Barcelona (ICMAB-CSIC)1,Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN)2
The first BEDT-TTF=bis(ethylenedithio)-tetrathiafulvalene based quasi two-dimensional organic superconductor β-(BEDT-TTF)<sub>2</sub>I<sub>3</sub> was reported back in 1984.<sup>[1]</sup> Soon it became clear that ion radical salts derived from BEDT-TTF exhibit tunable electronic band structures. Therefore, such molecules are excellent building blocks for engineering a rich and diverse family of organic crystalline metals and semiconductors. Such systems can be further tuned by choosing the nature of the IRSs enabling high sensitivity towards strain, pressure, humidity, temperature or even contact-less radiation sensing <i>i.e.</i> bolometers.<sup>[2</sup><sup>-4</sup><sup>] </sup>Composites exhibit unique synergistic properties emerging when components with different properties are combined. The tuning of the energy bandgap in the electronic structure of the material allows designing tailor-made systems with desirable mechanical, electrical, optical, and/or thermal properties.<sup>[5]</sup> Here, we discuss an emergent insulator−metal transition at room temperature in thin-films comprised of polycarbonate/molecular-metal composites. Temperature-dependent resistance measurements allow monitoring of the electrical bandgap, which is in agreement with the optical bandgap extracted by optical absorption spectroscopy. The semiconductor-like properties of our films, made with bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF or ET) α-ET<sub>2</sub>I<sub>3</sub> (nano)microcrystals as two-dimensional molecular conductor on one side and insulator polycarbonate as a second ingredient, are attributed to an emergent phenomenon equivalent to the transition from an insulator to a metal. This made it possible to obtain semiconducting films with tunable electrical/optical bandgaps ranging from 0 to 2.9 eV. A remarkable aspect is the similarity close to room temperature of the thermal and mechanical properties of both composite components, making these materials ideal candidates to fabricate flexible and soft sensors for stress, pressure, and temperature aiming at applications in wearable human health care and bioelectronics.<br/><br/>References:<br/>E. B. Yagubskii, I. F. Shchegolev, V. N. Laukhin, et.al., JETP Lett., (1984), 39, 12.<br/>E. Laukhina, R. Pfattner, L. R. Ferreras, et. al., Adv. Mater., (2009), 21, 1-5.<br/>R. Pfattner, V. Lebedev, E. Laukhina, et.al., Adv. Electron. Mater., (2015), 1, 1500090.<br/>R. Pfattner, E. Laukhina, L. Ferlauto, et.al, ACS Appl. Electron. Mater., (2019), 1, 1781.<br/>R. Pfattner, E. Laukhina, J. Li, et.al, ACS Appl. Electron. Mater. (2022), 4, 2432.