Dinaphthotetrathienoacenes: Synthesis, Characterization, and Applications in Organic Field-Effect Transistors

The charge transport of crystalline organic semiconductors is limited by dynamic disorder that tends to localize charges. It is the main hurdle to overcome in order to significantly increase charge carrier mobility. An innovative design that combines a chemical structure based on sulfur-rich thienoacene with a solid-state herringbone (HB) packing is proposed and the synthesis, physicochemical characterization, and charge transport properties of two new thienoacenes bearing a central tetrathienyl core fused with two external naphthyl rings: naphtho[2,3-b]thieno-[2''',3''':4'',5'']thieno[2″,3″:4',5']thieno[3',2'-b]naphtho[2,3-b]thiophene (DN4T) and naphtho[1,2-b]thieno-[2''',3''':4'',5'']thieno[2'',3'':4',5']thieno[3',2'-b]naphtho[1,2-b]thiophene are presented. Both compounds crystallize with a HB pattern structure and present transfer integrals ranging from 33 to 99 meV (for the former) within the HB plane of charge transport. Molecular dynamics simulations point toward an efficient resilience of the transfer integrals to the intermolecular sliding motion commonly responsible for strong variations of the electronic coupling in the crystal. Best device performances are reached with DN4T with hole mobility up to μ = 2.1 cm² V^-1 s^-1 in polycrystalline organic field effect transistors, showing the effectiveness of the electronic coupling enabled by the new aromatic core. These promising results pave the way to the design of high-performing materials based on this new thienoacene, notably through the introduction of alkyl side-chains.

Divanillin-Based Polyazomethines: Toward Biobased and Metal-Free π-Conjugated Polymers

Divanillin was synthesized in high yield and purity using Laccase from Trametes versicolor. It was then polymerized with benzene-1,4-diamine and 2,7-diaminocarbazole to form polyazomethines. Polymerizations were performed under microwave irradiation and without transition-metal-based catalysts. These biobased conjugated polyazomethines present a broad fluorescence spectrum ranging from 400 to 600 nm. Depending on the co-monomer used, polyazomethines with molar masses of around 10 kg·mol^-1 and with electronic gaps ranging from 2.66 to 2.85 eV were obtained. Furthermore, time-dependent density functional theory (TD-DFT) calculations were performed to corroborate the experimental results.

Molecular Semiconductors for Logic Operations: Dead-End or Bright Future?

The field of organic electronics has been prolific in the last couple of years, leading to the design and synthesis of several molecular semiconductors presenting a mobility in excess of 10 cm² V^-1 s^-1 . However, it is also started to recently falter, as a result of doubtful mobility extractions and reduced industrial interest. This critical review addresses the community of chemists and materials scientists to share with it a critical analysis of the best performing molecular semiconductors and of the inherent charge transport physics that takes place in them. The goal is to inspire chemists and materials scientists and to give them hope that the field of molecular semiconductors for logic operations is not engaged into a dead end. To the contrary, it offers plenty of research opportunities in materials chemistry.

Triaryl-1,4-diamine-based polysquaraines: effect of co-solvent and monomer insertion on optoelectronic properties

Emission of the synthesized polysquaraine (left) and CIE 1931 color space chromaticity diagram of the corresponding OLED (right).

Synthesis of squaraine-based alternated π-conjugated copolymers: from conventional cross-coupling reactions to metal-free polycondensation

Low band-gap π-conjugated copolymers based on squaraine units can be synthesized through classical Suzuki and Stille cross-coupling reactions (in blue), or through a metal-free polycondensation (in green).