Engineering of Plasmonic Hybrid Electrodes Passivated and Densified by IBAD for Organic Light-Emitting Diodes

To replace indium tin oxide (ITO) in flexible optoelectronics (OLEDs, photovoltaics), silver nanowire (AgNW) networks represent a viable and promising alternative. However, two major bottlenecks limit their industrialization: their high surface roughness, which causes short-circuits across thin organic active layers, and their chemical instability against atmospheric oxidation. To address these challenges, the ELITE team at XLIM has developed a protective multilayer configuration and surface functionalization techniques to lower both resistance and roughness while improving optical transmittance. On the electronic level, this functionalization drastically decreases the work function of the nanowires, reducing charge injection barriers. In parallel, the generation of hot electrons via the non-radiative damping of surface plasmons on AgNWs is attracting growing interest. To exploit these carriers, the metal/oxide interface must be perfectly controlled. A conventional solution-processed deposition of ZnO nanoparticles produces a porous film rich in electronic trap states that quench the hot carriers. Vacuum-based ion beam-assisted deposition (IBAD) enables the deposition of nanometrically thin, dense oxide layers at room temperature. The assisting ion bombardment densifies the film and modifies its band structure.

This PhD project aims to achieve a technological leap by combining these approaches within a single flexible OLED architecture. The primary objectives are:

• Control the microstructure and energy level alignment of oxides deposited at low temperatures on the XLIM PLATINOM platform, leveraging IBAD-driven densification to optimize hot electron transfer.
• Achieve a passivation by combining the grafting of nitrogen-containing molecules with the deposition of dense oxides to quench surface defects (such as oxygen vacancies) and precisely tune the work function.
• Map the band alignment in ambient air using PYSA to correlate the physical parameters of the IBAD deposition and organic grafting with the effective work function.

The doctoral school “Science and Systems Engineering” (SI) is directed by Prof. Anne JULIEN-VERGONJANNE. It covers the following disciplines: Mathematics, Microwaves, Photonics, Informatics, Images, Automatics and their Interactions. It delivers the following thesis references: Mathematics and applications, Informatics and applications, High frequency electronics, photonics and systems, Image, signal and automatic. It is attached to 4 institutions (COMUE Leonard de Vinci, Limoges University, Poitiers University and ASE/ENSMA in Poitiers). It relies on 3 partner laboratories: XLIM, LMA and LIAS. 250 doctoral students are enrolled in the doctoral school SISMI.

XLIM is a joined Research laboratory (UMR 7252) between the French National Research Center (CNRS) and the University of Limoges. It has a strong expertise in electronics and microwaves, optics and photonics, CAD, mathematics, computer sciences and image processing for the application in secured environments, biotechnology and health, energy control and saving. XLIM is a multidisciplinary research institute located on several geographical sites, and it incorporates more than 440 people among professors, CNRS researchers, engineers, technicians, post-doctoral researchers, PhD students and administrative staff (website: www.xlim.fr)

The “Printed Electronics for Telecoms and Energy” (ELITE) team at XLIM has been focusing for the last two decades on the electrical and optoelectronic characterization of organic and hybrid semiconductors and devices, with a special focus on third generation solar cells, light-emitting diodes, thin film transistors (see the group webpage). Major developments have been demonstrated in the group in the field of organic and hybrid devices, including hybrid perovskite materials and ink-jet printing technologies. More generally, the group is focusing on interfaces, which are crucial components for any functional device. The group is managing its own technology platform devoted to Printed Electronics, which is part of the PLATINOM facility, the technological resource center of XLIM, open to academic and industrial partners for developments in the field of RF components and circuits, and Photonics.

The successful candidate must hold a Research Master’s degree (Master 2) in Materials Physics, Nanotechnology, Optoelectronics, or Organic Electronics, and should exhibit an interdisciplinary profile at the interface of solid-state physics, materials science, and nanotechnology.

The ideal candidate should have a strong interest in laboratory work and physical vapor deposition (PVD) techniques. They could possess solid knowledge in semiconductor physics, ideally in plasmonics, as well as in surface characterization techniques such as AFM, SEM, ellipsometry, and absorption or emission spectroscopy. 

Rigorous, autonomous and self-motivated, the candidate will be expected to independently manage materials synthesis through to their final integration into complex optoelectronic devices. They must demonstrate excellent teamwork skills to actively collaborate with researchers from the XLIM team and engineers from the PLATINOM platform, while also displaying strong communication skills to draft scientific papers and present their work in English.