Growth and physical properties of crystalline rubrene - BOA Bicocca ...

Chapter 2
Rubrene: physical and
chemical properties
2.1 Introduction
Rubrene (5,6,11,12-Tetraphenyltetracene, C 42 H 28 ) is one of the most
promising small molecule organic semiconductors, showing record values for
most of the properties needed to build efficient devices, such as photocur-
rent generation efficiency, exciton diffusion length and charge carrier mobil-
ity[14, 16, 17]. At the same time it poses a lot of experimental challenges,
because of its chemical instability in the presence of oxygen, because of
the difficulties found in obtaining rubrene thin films with a good crystalline
quality and also due to the still limited understanding of the origin of its
most interesting properties, therefore not optimized yet. Thus, in this chap-
ter we will first focus on the description of what is currently known about
rubrene, and afterward we will indicate the main open problems connected
with rubrene, some of them to be addressed in the following chapters of this
work.
2.2 The molecule
Rubrene belongs to the group of polycyclic aromatic hydrocarbons and
consists of a tetracene backbone (i.e. four linearly fused benzene rings ) with
a phenyl ring bonded on each side of the two central benzene rings, as shown
by the structural formula and the three-dimensional sketch reported in figure