Antonio Valerio LONGO soutiendra sa thèse intitulé :
" Development of alternate-current thin-film electroluminescent devices based on manganese-doped zinc sulfide quantum-dot technology " le 10 décembre 2021 à 14h00 en salle 774 - Bâtiment Lavoisier – 15 rue Jean-Antoine de Baïf, 75013 Paris

Résumé :
In this work we address the development of a light-emitting device, based on manganese-doped zinc sulfide nanoparticles, working under the application of an alternate-current voltage. Our device is based on a simple capacitive configuration implying a single layer of spin-cast nanoparticles sandwiched between two insulating thin films. In the first part of our work, we studied the nanoparticle system from a fundamental point of view. These nanoparticles, synthesized without the use of any surfactant by a microwave-assisted synthesis, are characterized by a phosphorescence activity in the orange region of the visible spectrum stemming from manganese dopants. In our work, we have observed and studied an enhancement of this optical activity under
prolonged UV-light exposition. Our investigation allowed us to ascribe this phenomenon to a local lattice-strain effect around manganese chromophores due to a surface oxidation process induced by UV light. In a second part of our work, we focused on the dielectric properties of the insulating layers, consisting in an hafnium oxide film deposited by atomic layer deposition. By exploring several layer thicknesses and deposition temperatures, we have optimized the dielectric properties of the film, leading to more reliable and robust results. In the third part of our work, the main characteristics of the complete electroluminescent device are addressed. More specifically, we recovered the orange emission band due to manganese doping, as well as the typical threshold behavior of the intensity of the emitted light as a function of the applied voltage. By exploiting structural characterization, impedance spectroscopy measurements and a careful comparison with theoretical works on similar devices, we have been able to state that the mechanism behind the observed light emission is a field-induced charge-creation process within the active layer only, followed by charge transport across the layer and radiative recombination within a single nanoparticle. Compared to previous works based on manganese-doped zinc sulfide nanoparticles, our key point has been the use of uncoated nanoparticles which allowed to achieve a very compact nanoparticle arrangement, favoring the physical mechanism mentioned above.

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Jury de thèse:

Directrice de thèse :
- Pr. Souad Ammar, Université de Paris
Co-Directeur de thèse :
- Dr. Nicolas Battaglini, Université de Paris
Rapporteurs :
- Pr. Sébastien Chénais, Université Sorbonne Paris Nord
- Dr. Jean-François Hochepied, Mines ParisTech
- Dr. Dominique Mailly, C2N
Examinatrice :
- Pr. Angela Vasanelli, Université de Paris
- Dr. Ali Madouri, C2N