Modélisation, conception, fabrication et caractérisation de diode électroluminescente organique avec une microcavité à contre réaction répartie en régime d’excitation électrique impulsionnel
Modeling, design, fabrication and characterization of organic light emitting diodes with distributed feedback micro-cavity under ultra-short electrical pulsed regime
Résumé
This mainly experimental work aims at the design, micronanofabrication and characterization of a component combining an organic light-emitting diode (OLED) and a distributed feedback cavity (DFB) forward towards the organic laser diode.If the development of organic electronics has given rise to many optoelectronic components, the demonstration of organic laser diode remains a major issue despite a very recent publication by the Japanese Adachi team. There are several scientific challenges to realize the organic laser diode; firstly the organic semiconductors known as a low conductive materials and it can accept a low current density (100-1000mA/cm² in direct current) while the laser threshold is estimated beyond several kA/cm². Secondly, the annihilation losses due to the accumulation of triplet states appeared beyond ten nanoseconds increase the laser threshold. In the most favorable case, OLED included in a cavity with a high quality factor offering a low laser threshold, although without a specific materials with low annihilation rates, can offer a lasing effect in another configuration corresponding to a time window of less than 10ns and electrical pulses of the order of kA/cm².This thesis studies the electrical, optical and material aspects of the three components of an organic laser diode as knowing as a cavity, a gain medium, and an excitation source.The first chapter based in bibliographical study, allows to identify the stakes and to make a first series of choices to guide the continuation of the work.The second chapter of this work is devoted to designs and modeling. An improved electrical model compared to the state of the art is proposed which allows to design faster OLEDs with time constants of order of 100ps. This electrical model allows to design and fabricate components to meet the high current density requirements to reach the targeted laser thresholds. A dynamic laser model is then proposed that takes into account the electrical excitation and the dynamics of spontaneous and stimulated emissions. This organic laser diode model allows to predict the laser dynamics from key parameters such as the laser threshold. The third point studied is the laser cavity. A theoretical study based on 1D and 2D modeling has been performed to dimension the type of cavity to be manufactured. The third chapter, implements the conclusions of the previous chapter to fabricate the electrodes by photlithography, the DFB type cavity combining a first and a second order by electronic lithography, and the OLEDS by vacuum evaporation.Chapter four presents time-resolved electrical and optical measurements of the elementary components of the laser diode designed according to the results of the previous chapters. From OLED characterization, we validate the performs of a high speed OLEDs that it responses to a few hundred of ps and exceeds tens kA/cm² as a current density. Under optical pumping, the DFB cavities show quality factors of the order of several mills, which validates the design and fabrication. Finally, a series of components combining an ultrafast OLED, a DFB cavity made of a first order and a second order are characterized. First results show a more intense optical response with a DFB microcavity than without, which we can interpret as the beginning of Stimulated Emission Enhancement (SEA).
Le sujet de thèse présente une pertinence et une urgence scientifique aussi bien pour l'équipe PON (Photonique Organique et Nanostructure) du LPL que pour la Centrale de Proximité en Nanotechnologies de Pars Nord C(PN)2. Au niveau international, le sujet est pertinent et urgent, car le laser organique à l’état solide sous excitation électrique constitue le Graal hors d’atteinte pour plusieurs équipes de recherche mondiales ; (S. Forrest à Standford (USA), Y. Adachi au Japon, K. Leo à Dresde (Germany),…). Or de récentes avancées scientifiques obtenues au LPL et au sein de C(PN)2, qui constituent des premières mondiales en font le seul laboratoire au monde à disposer actuellement des connaissances et des technologies pour atteindre le seuil laser par excitation électrique. Ceci grâce à des impulsions de durée inférieure à 10ns et avec une densité de courant (6kA/cm²) suffisante pour dépasser le seuil laser. Le sujet est pertinent au niveau locale car il s'appuie sur les travaux préliminaires d’Alex Chime (soutenance décembre 2017) qui en combinant de façon pionnière l’électronique micro-ondes et l’optoélectronique organique a permis de mettre au point des électrodes micro-ondes coplanaires (coplanar waveguide) en oxyde d’étain et d’indium (ITO) compatible avec les OLED. Ceci a permis de diminuer d’un ordre de grandeur la durée des impulsions par rapport à l’état de l’art, de passer en dessous de la barre des 10ns (2.5ns), d’obtenir des densités de courant jusqu’à 6kA/cm² ainsi que des rendements quantiques internes jusqu’à 1.5 %. Ces résultats constituent 3 records mondiaux qui ont donnés lieux à des brevets et des publications [Pat. EP17306292.8] [Pat.EP173062.6] [ Zeng , IEEE Trans. El. Dev., 64,7, Jul. 2017][Chime, Org. Electron., 56, May 2018]. En capitalisant sur ces avancées obtenues récemment et en les combinant avec des microcavités à concevoir et à réaliser dans le présent projet de recherche doctoral la pertinence et la faisabilité sont garanties.
Domaines
Physique [physics]| Origine | Version validée par le jury (STAR) |
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