Description du sujet de thèse

Background & motivations: Designing high-efficiency solar cells without significantly increasing their manufacturing cost is a major current challenge. One of the most promising strategies is the realization of thin-film/silicon tandem solar cells, taking advantage of the industrially mature silicon technology. However, disruptive solutions are still required to fabricate tandem solar cells with power conversion efficiencies > 30% with low-cost and scalable processes. In particular, nanopatterning is at the heart of most strategies to enhance light absorption in thin and ultrathin single-junction solar cells [1], however often using costly and lab-scale techniques. In this context, it is key to develop low-cost and large-area nanopatterning techniques compatible with the integration in tandem solar cells.

Objectives of the project: The goal of the PhD project will be twofold : 1) developing a low-cost and upscalable nanopatterning process and 2) exploring the impact of controlled disorder on light management in thin absorbing layers, with the target to integrate nanopatterned surfaces into tandem solar cells within the duration of the thesis. The main patterning process envisioned in the project is sparse colloidal lithography using the self-assembly of charged colloids under the effect of electrostatic interactions to create nanophotonic surfaces with correlated disorder [2]. It is versatile, not very sensitive to the topography of the substrate and allows a parallel structuring on a large surface. A strong motivation behind the PhD project is to investigate nanopatterned surfaces with correlated, and in particular hyperuniform, disorder that could combine the advantages of both periodic and disordered structures, such as achieving a tailored optical response while offering a high tolerance to fabrication defects.
Techniques: The PhD student will work on both modelling, fabrication and characterization aspects. He or she will learn numerical optical simulation methods and use dedicated optical characterization setups. He or she will be trained on different micro and nano fabrication techniques as well as related characterization techniques (SEM, AFM, ellipsometry,…). He or she will also get full training on standard clean-room techniques.

[1] I. Massiot, A. Cattoni and S. Collin, Nature Energy 5, 959-972 (2020).
[2] P. M. Piechulla et al., Advanced Optical Materials 1701272 (2018).

Contexte de travail

The PhD project will take place between the Laboratory of Analysis and Architecture of Systems (LAAS-CNRS, Team PHOTO, https://www.laas.fr/public/fr/photo) in Toulouse and the Center for Nanoscience and Nanotechnology (C2N, SUNLIT Team, https://sunlit-team.eu/) in Palaiseau. The PhD student will benefit from both high-quality scientific environments with access to state-of-the-art clean room equipment and excellent doctoral training.