The emission of stable and efficient blue light is a major issue in organic technologies.
Our works have made it possible not only to obtain new highly efficient organic semiconductors (Angew. Chem. 2015, Adv. Funct. Mater 2018) but also to shed new light on fundamental concepts such as the impact of molecular arrangement on the evolution of the energy of frontier orbital and singlet and triplet states (Acc. Chem. Res. 2018, Chem. Comm. 2019-Feature article). Thus, by modifying the intensity of the electronic coupling between two π-conjugated fragments by steric and / or electronic effects, we have shown that it was possible to selectively modulate the energies of the frontier orbitals while keeping a very high level of energy of the triplet state, essential property for an application as a host matrix in a PhOLED (ACS Appl. Mater. Interfaces, 2017).
These works allow today the creation of very efficient molecular systems for organic semiconductors.
The group is today a leading group in the design of host materials for PhOLEDs and works in collaboration with recognized teams in the development of electronic devices (University of Shoochow-China, LPICM / École Polytechnique-France).
Since 2013, we have been developing new families of electron acceptors built on various organic skeletons: oligophenylenes and indacenothiophenes (ACS Appl. Mater. Interfaces, 2017) and bithiazolidinylidene-tetrathione and birhodanins (J. Mater. Chem. C 2015) .
In particular, in the case of bithiazolidinylidene-tetrathiones, we obtained mobilities of up to 0.29 cm2 V-1 s-1.
The various structural modifications made to this family of acceptors and their studies within devices have made it possible to identify the importance of chalcogen ∙∙∙ chalcogen interactions on the great stability of these devices in air (J. Mater. Chem . C 2017).
These acceptors can also generate charge transfer complexes with different donors such as pyrene, perylene and coronene. Within devices, these complexes have ambipolar properties dependent on interchain interactions (CrystEngCom. 2019).
This work is the subject of a sustained collaboration with Pr T. Mori of the Tokyo Institute of Technology (TITech).
Single-component molecular conductors
We have also developed a family of stable radicals, such as the dithiolene complexes of neutral free radical gold [Au (dithiolene)2] • (ρ = 1) obtained by oxidation of anionic complexes d8 with closed layer [Au (dithiolene)2]- . These dithiolene complexes form unidimensional one-dimensional chains with high conductivities (Chem. Eur. J. 2017) and behave like Mott insulators with very small gap (Phys. Rev. B 2018). We have shown that the use of physical pressure or short electrical pulses makes it possible to generate a resistive switching between two states, an initial insulating state (state '0') and a metallic state (state '1') (J. Phys. Chem. C 2015), a property that can be valued in electronic memories of the "Resistive Random Access Memories" (RRAM) type. Different structural modifications have been developed in order to better understand the structure / organization / property relationships. The first radical molecular dithiolene complex which behaves like a metal at ambient pressure has thus been obtained ([Au (Me-thiazdt) 2] •, J. Am. Chem. Soc. 2018).