PhD M/F

Job Description

Thesis Subject

From Hot Carriers to Excitons: Ultrafast Dynamics and Fine Structure
in Metal Halide Perovskites
Metal halide perovskites (MHPs) have emerged as a disruptive class of semiconductors, combining exceptional optoelectronic performance with low-cost and scalable fabrication. Their rapid rise has propelled them to the forefront of next-generation technologies, with applications spanning high-efficiency photovoltaics, light-emitting devices, spintronics, and quantum photonics. This versatility stems from their unique physical properties, including a highly tunable bandgap, strong spin–orbit coupling, long carrier diffusion lengths, and an unusual tolerance to defects.
Yet, despite their impressive macroscopic performance, a detailed microscopic understanding of carrier dynamics in MHPs remains incomplete. In particular, the role of lattice structure, dielectric screening, and local symmetry breaking in shaping carrier relaxation, recombination pathways, and spin properties is still under active debate. A central challenge is to unravel how these factors influence not only carrier cooling and trapping, but also the fine structure of excitonic states.
Following non-resonant optical excitation, high-energy photons generate hot carriers that rapidly thermalize through carrier–carrier scattering before relaxing toward the band edges via carrier–phonon interactions. In MHPs, this cooling process is often anomalously slow, a phenomenon attributed to strong electron–phonon coupling and the emergence of a hot-phonon bottleneck. However, such non-resonant excitation schemes inherently mask the intrinsic properties of band-edge states by involving a cascade of relaxation processes.
In contrast, resonant excitation directly addresses the band-edge excitonic states, providing a powerful and selective way to probe their intrinsic dynamics without the complexity of hot-carrier relaxation. This approach opens access to subtle effects such as exciton fine structure splitting, spin-dependent interactions, and coherent dynamics, which are critically influenced by crystal symmetry, spin–orbit coupling, and structural distortions.
This project aims to go beyond conventional carrier dynamics by combining non-resonant and resonant excitation schemes to disentangle the hierarchy of relaxation processes and access the fundamental properties of excitons in MHPs. A particular emphasis will be placed on understanding the fine structure of excitonic states, including the role of exchange interactions, spin splitting, and symmetry breaking, and how these features are affected by structural quality, disorder, and dielectric environment.
The PhD project will pursue three main objectives:
(i) to map the full dynamics of charge carriers from the hot-carrier regime down to band-edge excitons over timescales ranging from femtoseconds to nanoseconds;
(ii) to investigate the impact of trapping states and defects on both carrier relaxation and exciton recombination;
(iii) to probe and quantify the exciton fine structure using resonant optical techniques, and establish direct correlations with the structural and electronic properties of the material.

Your Work Environment

The PhD candidate will work at the Paris Institute of Nanoscience (Institut des NanoSciences de Paris, INSP), a Joint Research Unit (UMR 7588) affiliated with the French National Centre for Scientific Research (CNRS) and Sorbonne University. Directed by G. Prévot, INSP is an interdisciplinary research laboratory located on the Pierre and Marie Curie campus of Sorbonne University in Paris. The institute is dedicated to the study of nanostructures, quantum materials, nanophotonics, and mesoscopic physics, combining both experimental and theoretical approaches.

The host group will be the PHOCOS team (Photonics and Spin Coherence), which investigates the optical and quantum properties of innovative materials. Its research focuses on photonics, spin coherence, nanomaterials, perovskites, and quantum phenomena, with applications in optoelectronics and quantum technologies. The team combines state-of-the-art experimental techniques—including optical spectroscopy, magneto-photoluminescence, and ultrafast measurements—with theoretical modeling.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

The research professions