14 Décembre – Thesis defense - Alexandre Bachelet

10 h Amphi Jean-Paul Dom - laboratory IMS / building A31 (Talence campus)

Interfaces and structure studies of organic light-emitting transistors.

The organic light-emitting transistor (OLET) has attracted extensive attention from organic electronics research community. Its specificity is the combination of the electronic properties of the field-effect transistor with the light-emitting properties of the light-emitting diodes. Thus, it promises a major step forward to the simplification of circuit engineering in display technologies. The performances shown by OLETs make them potential candidates of the electrically pumped organic laser that still remains as a major challenge. It is in this context that this work of Ph.D. focused on the study of the structure of OLETs and their interfaces. As a first step, a viable architecture with reproducible performances was established through the investigations of different structures and materials. Optimisation on this structure was then carried out by integrating interfacial layers. The roles of hole blocking molecules were compared decoupling electron injection and hole blocking efficacies. OLETs with operating voltage as low as 5 V have been achieved. Cavity effect was observed in these OLETs, thanks to the specific structure where gate and drain both are composed of Al metal. Colour tuning in all visible light was realized simply by changing the emissive layer thickness. Subsequently, optical simulations were carried out to explain these phenomena. Further studies were carried out to enhance the current densities of our OLETs. Molecular doping and substrate temperature-controlled deposition were the two approaches explored. Although higher current densities were obtained, optical performances were not improved. In parallel, the integration of better gain-medium materials for lasing emission was attempted, in which a guest-host system was successfully developed.

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