La matrice de transmission permet de décrire les effets produit par un milieu multi-diffusant sur une onde monochromatique incidente. L'objectif des travaux présentés dans cette thèse est de développer le concept de matrice de transmission d'un milieu multi-diffusant au cas plus général d'une onde polychromatique impulsionnelle ultra-brève. Dans ce manuscrit nous présentons et mesurons la matrice de transmission multi-spectrale d'un milieu complexe. Cette nouvelle matrice nous donne l'information fondamentale sur le couplage spatio-temporel et spatio-spectral que le milieu engendre au passage d'une onde ultra-brève. Elle permet aussi de contrôler une source monochromatique et polychromatique, après avoir traversé un milieu complexe, de manière déterministe. Nous exploitons ainsi cette connaissance du milieu pour compenser les distorsions du champs en focalisant, façonnant et contrôlant spatialement, spectralement et temporellement un laser ultra-bref grâce à la seule mesure d'une matrice de transmission multi-spectrale. Cette méthode ouvre les portes de plusieurs applications d'imagerie à travers des milieux complexes, ainsi que pour l'interaction lumière-matière en milieux diffusants. / The transmission matrix allows to describe the effects generated by a multiple scattering medium on an incident monochromatic wave. The aim of the work presented in this dissertation is to develop the concept of transmission matrix of a multiple scattering medium to the more general case of a polychromatic ultra-fast pulsed light. In this dissertation we present and measure the multi-spectral transmission matrix of a complex medium. This new matrix describes the spatio-temporal coupling and the spatio-spectral coupling induced by the medium on a polycrhomatic illumination passing through it. The measurement of the multi-spectral transmission matrix allows us to control a monochromatic as well as a polychromatic source, after being scattered by the medium, in a deterministic way. We exploit this knowledge about the medium to compensate the distortions of the optical field by focusing, shaping and controlling spatially, spectrally and temporally an ultra-fast laser, thanks to the knowledge of the multi-spectral transmission matrix. This method paves the way towards many applications in the domain of imaging and light-matter interaction of light through complex media.

Abstract: Understanding and controlling the ultrafast charge carrier and exciton dynamics at the interface of semiconductor nanocrystals (NCs) offer an excellent opportunity to improve the charge collection and the overall performance of many optoelectronic and energy-based devices. In this dissertation, we study how interfacial engineering of these materials can have a direct influence on controlling the charge transfer and the nonradiative losses in different donor-acceptor systems. The first introductory chapter provides an overview of all the fundamental photophysical processes controlling the interfacial phenomena. Then, the second chapter highlights all the chemicals and synthesis methods employed during this thesis. The subsequent two chapters discuss the detailed experimental studies and observations related to different materials and interfaces. First, it describes how we can dramatically tune the intersystem crossing (ISC) rate, the triplet state lifetime, turn on/off the electron injection at the CdTe-Prophyrin interface via tuning either the quantum dot size or the porphyrin molecular structure. Also, how the intermolecular distances, electronic coupling, and subsequently, the photoinduced charge transfer can be controlled by the interfacial electrostatic interactions at CdTe-Fullerene interfaces. Second, due to the promise that of perovskite NCs holds for improving many solar cell and optoelectronic applications, chapter 3 highlights the tremendous effect that the shape of perovskite nanocrystals has on the rate and the mechanism of charge transfer at the MAPbBr3- TCNE interface. Besides, it demonstrates how the confinement effect brought by changing the dimensionality influence the charge transfer dynamics at the MAPbBr3-BQ interface. Finally, it explains how the effective passivation of the surface defects and the subsequent suppression of the formation of surface nonradiative recombination centers in CsPbCl3 NCs controls the photoluminescence quantum yield and the photodetector performance.