White organic light emitting diodes (WOLEDs) are promising devices for application in low energy consumption lighting since they combine the potentialities of high efficiency and inexpensive production with the appealing features of large surfaces emitting good quality white light. However, lifetime, performances and costs still have to be optimized to make WOLEDs commercially competitive as alternative lighting sources. Development of efficient and stable emitters plays a key role in the progress of WOLED technology. This tutorial review discusses the main approaches to obtain white electroluminescence with organic and organometallic emitters. Representative examples of each method are reported highlighting the most significant achievements together with open issues and challenges to be faced by future research.

In this article we highlight, by means of selected examples drawn from work performed in our or other laboratories, the features of some classes of fluorinated conjugated materials and their use in electronic devices such as electroluminescent diodes or field effect transistors. A variety of fluorinated conjugated systems, either molecular or polymeric, such as poly(phenylenevinylene)s, poly(phenyleneethynylene)s, polythiophenes, polyphenylenes, are dealt with. Attention is also focused on a different class of electroluminescent compounds, represented by the cyclometalated iridium complexes with various forms (mer and fac). In particular, fluorine atoms lower both the HOMO and LUMO energy levels. Consequently, the electron injection is made easier, the materials display a greater resistance against the degradative oxidation processes and organic n-type or ambipolar semiconducting materials may result. Moreover, the C-H...F interactions play an important role in the solid state supramolecular organization, originating a typical pi-stack arrangement which enhances the charge carrier mobility.

Organic thin-film transistor sensors have been recently attracting the attention of the plastic electronics community for their potential exploitation in novel sensing platforms. Specificity and sensitivity are however still open issues: in this respect chiral discrimination-being a scientific and technological achievement in itself--is indeed one of the most challenging sensor bench-tests. So far, conducting-polymer solid-state chiral detection has been carried out at part-per-thousand concentration levels. Here, a novel chiral bilayer organic thin-film transistor gas sensor--comprising an outermost layer with built-in enantioselective properties-is demonstrated to show field-effect amplified sensitivity that enables differential detection of optical isomers in the tens-of-parts-per-million concentration range. The ad-hoc-designed organic semiconductor endowed with chiral side groups, the bilayer structure and the thin-film transistor transducer provide a significant step forward in the development of a high-performance and versatile sensing platform compatible with flexible organic electronic technologies.

Homoleptic Ir(Fnppy)3 and heteroleptic (Fnppy)2Ir(acac) complexes (n = 3: F3ppy =\ud 2-(39,49,69-trifluorophenyl)pyridine; n = 4: F4ppy = 2-(39,49,59,69-tetrafluorophenyl)pyridine;\ud acac = acetylacetonate) have been synthesized and their spectroscopic properties investigated. The\ud homoleptic complexes exist as two stereoisomers, facial (fac) and meridional (mer), that have been\ud isolated and fully characterized. Their electrochemical and photophysical properties have been\ud studied both in solution and in the solid state and electroluminescent devices have been fabricated.\ud The emissive layers in devices have been obtained mixing the iridium complexes with a PVK\ud [poly(9-vinylcarbazole)] host matrix, in the presence of the electron carrier Bu-PBD [2-(4-\ud biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole]. The application of a voltage (5.0–6.5 V)\ud between the electrodes of devices leads to electro-generated blue luminescence which has similar\ud energy to the solution emissions. Interestingly, the stability of the devices made with the\ud homoleptic fluorinated iridium complexes strongly depends on the stereochemistry of these\ud phosphors and high (up to 5.5%) external quantum efficiencies for the fac complexes are\ud measured

Synthetic melanin based metal–insulator–semiconductor devices are fabricated for the first time thanks to silicon surface wettability modification by using dielectric barrier discharge plasma. Ambipolar charge trapping in air and ion drift mechanisms under vacuum are identified by capacitance–voltage hysteresis loops. These results aim to foresee the possible integration of synthetic melanin layers as a novel capacitor in organic polymer based devices.