Azaacenes Based Electroactive Materials: Preparation, Structure, Electrochemistry, Spectroscopy and Applications—A Critical Review

This short critical review is devoted to the synthesis and functionalization of various types of azaacenes, organic semiconducting compounds which can be considered as promising materials for the fabrication of n-channel or ambipolar field effect transistors (FETs), components of active layers in light emitting diodes (LEDs), components of organic memory devices and others. Emphasis is put on the diversity of azaacenes preparation methods and the possibility of tuning their redox and spectroscopic properties by changing the C/N ratio, modifying the nitrogen atoms distribution mode, functionalization with electroaccepting or electrodonating groups and changing their molecular shape. Processability, structural features and degradation pathways of these compounds are also discussed. A unique feature of this review concerns the listed redox potentials of all discussed compounds which were normalized vs. Fc/Fc+. This required, in frequent cases, recalculation of the originally reported data in which these potentials were determined against different types of reference electrodes. The same applied to all reported electron affinities (EAs). EA values calculated using different methods were recalculated by applying the method of Sworakowski and co-workers (Org. Electron. 2016, 33, 300–310) to yield, for the first time, a set of normalized data, which could be directly compared.

Expect the unexpected: more possibilities for organic electronics

There are a plethora of devices and phenomena that have been explored beyond the more conventional topics covered in the previous eight chapters. In this chapter, several of these interesting and promising topics in organic electronics are introduced. These include electrochemical light emitting devices, strong coupling between excitons and photons in optical microcavities forming so-called exciton polaritons and their associated devices, organic memory devices, and organics in limited dimensional systems. This latter topic includes discussions of energy transfer between organics and two-dimensional electronic materials, and single molecule, one-dimensional devices and phenomena. In each case, the discussions begin with an introduction to the subject, followed by laying the theoretical foundations of device operation, and finally by presenting several exemplary results that illuminate critical concepts. The purpose of this choice of topics is to show the endless horizons that are open to further investigation in the field of organic electronics.