Luminescent Re(I) and Ir(III) complexes: from design to application in light-emitting devices
Tesi di Dottorato
Data di Pubblicazione:
2009
Citazione:
Luminescent Re(I) and Ir(III) complexes: from design to application in light-emitting devices / M. Mauro ; tutor: G. D'Alfonso ; coordinatore: F. Cozzi. DIPARTIMENTO DI CHIMICA INORGANICA, METALLORGANICA E ANALITICA "Lamberto Malatesta", 2009 Dec 16. 22. ciclo, Anno Accademico 2008/2009.
Abstract:
In the past two decades, luminescent materials have attracted enormous interest due to their great photophysical and electrochemical properties. Such compounds have shown potential in biological imaging and, most important, as photoactive components for electroluminescent materials (i.e. OLEDs and LEECs), as well as sensitizers in solar cells[3]. In some case they became a real market technology to date. The most powerful driving forces for the research in such field are the pursuit of renewable non-oil based energy sources (solar cells application) and of more efficient lightening devices (OLED).
The development of organic light-emitting devices (OLEDs) started with the discovery of the electroluminescence from polymer OLEDs 25 years ago. Afterwards, the development of thin-film heterojunction devices based on Alq3 (Aluminum tris-quinolinate) by Tang and Van Slyke in the 80s opened the commercial interest to such a device in display and lighting technology.[4]
Indeed, the optical stimulation is not the only way to generate an excited state. In some case, the charge recombination reaction between the electrically-generated reduced and oxidized forms of the same compound may lead to the formation of an excited state which could radiatively relax, with emission of a photon. In this respect, complexes containing transitions metals such as Ru(II), Re(I) and Ir(III) are particularly appealing since they are able to exhibit luminescence upon electrical stimulation.
The presence of a heavy metal atom in transition metal complexes could induce a considerable degree of spin-orbit coupling to such an extent that spin-forbidden electronic transitions may become sufficiently allowed. This effect is particularly evident for complexes of metals belonging to the second and third row of the transition metals block (mainly Pt, Ir, Re, Os and Ru).
Differently to the fluorescent-based OLEDs, the phosphorescent-based ones can efficiently make use also of the electrically generated exciton with triplet spin, increasing the theoretical efficiency limit up to 100%.[5]
In this Ph.D. thesis we have focused our attention on luminescent Re and Ir complexes able to act as phosphorescent emitters in electroluminescent devices. In collaboration with other universities and industrial research groups (Prof. L. De Cola, Universität Münster and Center for Nanotechnology, Münster (D); Ciba Inc., Basel (CH) and National Chiao Tung University, Hsinchu (Taiwan)), we have designed, synthesized and characterized several highly emitting Re and Ir complexes in order to develop molecules possessing the desired properties.
Our aim is to find new classes of stable phosphorescent emitters, suitable for monochromatic and/or white-light OLEDs (i.e. Re complexes) as well as compounds containing multi-redox centres with externally and deliberately adjustable photophysical properties (i.e. Ir complexes), which can be useful for reduction of small molecules (H2O, CO2, ...). In this project, we have carried out tailored synthesis with joint experimental and theoretical studies on a series of Re and Ir complexes in order to gain a deeper insight into the electronic processes involved in these classes of compounds. Some of these materials were also successfully tested as emitting dopants in electroluminescent devices.
This thesis is basically divided in four main sections:
1. New class of Re complexes and their application in OLED;
2. Re-based LEECs;
3. A new class of porous materials consisting of charged iridium complexes;
4. New amphiphilic luminescent iridium complexes able to self-organize.
Section 1. Several parameters are important for describing the efficiency of an OLED, and one of these is the emission quantum efficiency of the materials, em. Although the
Tipologia IRIS:
13 - Tesi di dottorato discussa entro ottobre 2010
Elenco autori:
M. Mauro
Link alla scheda completa: