Air stability of PTCDI‐C13‐based n‐OFETs on polymer interfacial layers

This Letter reports the novel use of poly(9‐vinylcarbazole) (PVK) as a dielectric interfacial layer for n‐type organic field‐effect transistors (n‐OFETs). With PVK, both the air stability and electron mobility of N,N′‐ditridecylperylene‐3,4,9,10‐tetracarboxylic diimide (PTCDI‐C13)‐based OFETs were improved. Among the PVKs with different weight‐average molecular weight (M_w), PVK with high M_w showed good performance. The high glass transition temperature of PVK enabled thermal post annealing of the active layer, which resulted in a high electron mobility of 0.61 cm²/Vs. This mobility was maintained at 90% and 59% after 4 days and 105 days in air, respectively. The PVK interfacial layer reduced the trapped charges in the PTCDI‐C13‐based n‐OFET for air‐exposure and caused a decrease in the threshold voltage shift.

     

Self-assembly,optical and electrical properties of fork-tailed perylene bisimides

Effect of side-chain length on self-assembly, optical and electrochemical properties of N,N′-di(1-pentylbutyl)perylene-3,4,9,10-tetracarboxylic bisimide and N,N′-di(1-hexylpentyl)perylene-3,4,9,10-tetracarboxylic bisimide has been studied. The photo-physical, thermal and electrochemical properties were studied using UV–Vis and fluorescence, differential scanning calorimetry, and cyclic voltammetry, respectively. The molecules self-assembled as 1D – rods and molecular bundles, self-assembly was studied using SEM, optical and fluorescence microscopic techniques. The results concluded that the compound with short tail exhibits low solubility and self-assembled faster. The photo-physical properties of the compounds were not much affected by varying the alkyl chain length. The compounds geometries were optimized at 6-31G^∗ using DFT and the potentials were correlated with molecular orbitals.     

First principle study of a bimolecular thin film on Ag(1 1 1) surface

The formation of melamine–PTCDI bimolecular networks deposited on Ag(1 1 1) is studied by means of first principle calculations. Emphasis is placed on the interplay of the inter-molecular hydrogen bonds and the molecule–substrate contacts. Our simulations show rather strong distortions of the adsorbed molecules near the contact points due to the influence the hydrogen bonds. Despite this, the charge transfer from the substrate to a PTCDI molecule remains almost the same (0.9 e⁻) as obtained for an isolated PTCDI molecule. A detailed analysis of the topological features of the electronic density reveals that the charge transfer modifies the two types of hydrogen bonds in opposite ways, weakening the central bond and strengthening the two lateral ones, while roughly keeping a constant binding energy. Altogether, the influence of the substrate on the molecular network is proved to be weak.     

Direct synthesis of highly pure perylene tetracarboxylic monoimide

A series of perylene tetracarboxylic monoimides substituted with cycloalkanes were synthesized through a one-step reaction between cycloalkyl amines and the parent perylene dianhydride. The reaction demonstrates high selectivity for the production of monoimides with no formation of diimides. The high reaction selectivity is primarily due to the insolubility of the monoimides in the reaction medium, which in turn causes rapid precipitation of the products, shifting the reaction equilibrium to the right.