Theoretical and experimental studies of the polarized light's propagation into OLED structure

In collaboration with chemists from CEA Saclay and the University of Rennes, Leti's LCEM laboratory is interested in new chiral molecules for OLED (Organic Light Emitting Device) sources able to emit circularly polarized light (CP). The interest of these CPOLED sources is multiple and encompasses both micro-screens and healthcare applications. While the state of the art is quite extensive on the chemical part, few studies have looked at the generation and transport of light in CPOLEDs components.Likewise, the conditions for measuring the polarity of the light emitted are not very detailed in the existing literature.
At the LCEM laboratory, where these chiral molecules are integrated into CPOLED devices, the goal is to design OLED architectures that can better preserve the polarization of light. To do this, it is essential to understand the propagation of light in OLED stacks from a theoretical and experimental point of view. This work is part of a larger collaboration set up in the ANR "i-chiralight" project.
In this context, we are proposing a study which will take place in two phases.
- Study of simple emitting materials: The materials to be studied will be thin layers deposited under vacuum using evaporation's system of thin layers available in the laboratory. The organic materials used will be supplied by our chemical partners in Saclay or Rennes. Optical characterizations such as ellipsometry,photoluminescence, etc. will be carried out in order to assess the performance of molecules in terms of emission efficiency but also in terms of the rotational power of light. For this last point, a model able to calculate all the terms of the Müller matrices is under development and the validation of this one will be a work to be carried out by the post-doctoral fellow.
- Study of complete OLED components: In the second phase of this work, we will focus on the complete OLED system by studying the propagation of optical modes in the stack of the different layers const

Study and evaluation of a micro resonator based thermal sensor for uncooled infrared imagery

The project aims at establishing the feasibility of a novel infrared microbolometer sensor exploiting the thermal sensitivity of a free oscillating micro-nano-mechanical system (M & NEMS), whose resonant frequency changes with the infrared flux it absorbs. This is a concept out who was the subject of three patents.
The project addresses the needs of high resolution uncooled infrared imaging sensors (spectral band ranging from 8µm to 12µm) which is presently in expansion but whose next generation of products is still waiting for a breakthrough to reduce the pixel size, a key factor to improve performance and reduce the cost.
The objective of this post doctoral study is to achieve a proof of concept of this new architecture. In this outlook, the study will cover first the sizing of the device, then its design, implementation and validation at a single pixel level.

Design of integrated photonics modules

Design of next generation optoelectronic transceivers (particularly on-board modules) requires the merging of two advanced technologies: Silicon Photonics and 3D Silicon Packaging, both being developed at Leti.
In order to meet the requirements in term of technical specifications, cost and density, it is needed to achieve a codesign involving mechanical, thermal, optical and mainly RF aspects.
The aim of the work consists in designing such integrated modules by optimizing the RF interconnections of the module (internal and external), and the proper setup of the integrated circuits (ASICs). Modelling of several architectures will be led under HFSS and ADS softwares.
Finally, the integration of the module into its system environnement will be taken in charge, so as its characterization (involving testboard and testbench design).

Nanocrystal synthesis

This study aims at the chemical synthesis of infrared emitting nanocrystals for integration in LEDs.
These nanocrystals will be characterized by TEM, XRD, EDX, UV-vis, PL, NMR, FTIR. Formulation of colloidal solutions suitable for deposition via inkjet printing.
The candidate will work in the partner lab INAC/LEMOH

Electro-optical characterisation for Vis-IR active devices

With the Integration of Heterogeneous Components Department, the Lab of Technologies and Components for Visualisation (DIHS/LTCV) develops OLED devices. One of its main topics is aimed at producing hybrid OLEDs, hybrid standing for the mix of deposition techniques : wet and evaporation. Target applications come from micro displays to photodetectors via lighting.
For the development of hybrid OLEDs, DIHS/LTCV lab is looking for a Post_doc specialised in Organic Electronic to work in a fundamental research project. You will be in charge of stack development and of the characterisation method development for OLEDs devices.The optimisation of the cavity will be done based on the physical parameters of the different layers.
At the same time, IV, CV and photoluminescence analyses will be adapted in visible and IR range.
Finally, the layers interface study by impedance spectroscopy and Hall effect will be done.