Abstract
POLYPHON challenges how modifications in the lattice dynamics of organic semiconductors (OSC) reflect in a change of their electronic properties. POLYPHON exploits a robust synergic approach between precise structure definition, lattice dynamics and electronic transport, always combining experiments and theoretical modelling. Such a knowledge is of significant value because of the lack of predictive understanding of the inter-relationship between solid-state packing and performance of the device. Thus, despite OSC are attractive candidates as active layers in several new technologies, their use is currently hampered. In fact, different crystal structures (i.e. polymorphs) are available for the same molecular compound. Different polymorphs also have different vibrational patterns, which return different electron-phonon coupling (EPC), shaping the transport behaviour. Thus, polymorphism has a deep, but yet unpredictable, impact on OSC electronic properties. POLYPHON tackles its ambitious goals by addressing classes of molecules (further detailed in part B) like variably substituted, also asymmetric, BTBT, DNTT, TIPS and TMTES; and charge transfer compounds like (BTBT)(F -TCNQ/TCNNQ). x Each class will be first investigated by XRD in bulk as pre-screening, in mutual assessment with Raman, to fasten the subsequent work on thin films. The latter, necessary for most of real-world OSC applications, will be studied by identifying the actual substrate-selected polymorphs, including mixed phases, for the proper evaluation of the EPC, and via transport experiments in FET, Hall effect and van der Paw geometries, also with alternated current up to 1 GHz. Characterizations at different temperatures will enable to explore the polymorph landscape and phase diagram. Inhomogeneous mixed phases will receive special attention, the boundaries between different polymorphs will be investigated, mainly computationally, and included in the transport simulations, with continuous mutual feedback with the experiments. Transport simulations will follow a semiclassical approach developed by the PI (github.com/PatrizioGraziosi/ELECTRA) where the EPC can be fully considered in the anisotropic evaluation of the atomistic scattering rates, and where extrinsic effects, like mixed phases, can be included. POLYPHON’s comprehensive approach will allow to: i) achieve fundamental and transferrable knowledge on how the polymorphism impacts on the electronic properties with the possibility to be predictive on how a change in the lattice dynamics will reflect in a change in the electronic properties; ii) disentangle molecular structure, solid-state packing, nature and quantity of polymorphs, nature of the boundary between polymorphs, in respect of the electronic properties; iii) recognize how the substrate nature selects metastable polymorphs; iv) release to the community open-source simulation tools for the data analysis and the modelling of polymorphic OSC.
Dettagli del progetto
Responsabile scientifico: Elisabetta Venuti
Strutture Unibo coinvolte:
Dipartimento di Chimica Industriale "Toso Montanari"
Coordinatore:
CNR - Consiglio Nazionale delle Ricerche(Italy)
Contributo totale Unibo: Euro (EUR) 67.473,00
Durata del progetto in mesi: 24
Data di inizio
28/09/2023
Data di fine:
28/02/2026
