Advanced Materials and Surfaces
Implant materials fail due to unexpected corrosion upon their implantation in the complex physiological environment of the human body, with detrimental implications to patient health and safety. Key to the development of improved implant materials is an in-depth understanding of the link between material microstructure, surface oxide state, and surface reactivity.
- Analytical Chemistry, Education, Inorganic Chemistry
- Master Thesis
Hybrid organic-inorganic perovskite solar cells have achieved certified efficiencies of 25.7 % within a decade. This quick development is partially attributed to facile fabrication of high quality, polycrystalline perovskite films by solution-based methods. However, to crystallize the as-deposited perovskite films, post-annealing treatment is required. This is normally done at elevated temperatures (up to 170 °C) for 10 – 30 min, which drastically prolongs the processing time and thus the fabrication cost. Moreover, thermal annealing exposes the underlying layers equally to heat, which potentially harms the heat-sensitive materials in the stack and also limits the choice of materials for perovskite solar cells.
Flash lamp annealing (FLA) is a promising approach to squeeze the annealing time of the as deposited films to seconds, thus enabling a cost-effective production and further offers a new way to fabricate high quality perovskite films rapidly. FLA uses ultra-short pulses of intense broadband light flashes to selectively crystallize the as-deposited layer while keeping the bottom layers relatively intact, which allows using heat-sensitive, flexible substrates for perovskite solar cells fabrication.
- Chemical Engineering, Chemistry, Electrical and Electronic Engineering, Materials Engineering, Physics
- Master Thesis, Semester Project
Tandem solar cells outperform single junction solar cells by reducing thermalization losses. At Empa, we work on developing highly efficient perovskite-based thin-film tandem devices, which require a high-performance 1.8 eV wide bandgap perovskite with excellent uniformity on large-area substrates. To scale-up wide bandgap perovskites, either solution-based or vapour-based methods are used.
However, each of these methods has its own pros and cons. For example, solution-based methods allows facile compositional engineering and passivation additives can directly be mixed into the solution, but toxic solvents (e.g. DMF) are normally used and coatings on rough substrates are challenging. On the other hand, vapour-based methods conformally coat rough substrates, but controlling the composition of the perovskite is very challenging.
In our lab, we have developed a scalable hybrid PVD/blade coating process to fabricate efficient 1.57 eV perovskite solar cells. This process combines the merits of both methods: facile compositional engineering, efficient passivation management with additives, conformal coatings and non-toxic solvents only, thus being very promising for all-perovskite tandem devices. Ultimately, the uniformity is further enhanced by replacing the solution-based blade coating step with slot-die coating.
- Chemistry, Electrical and Electronic Engineering, Interdisciplinary Engineering, Manufacturing Engineering, Materials Engineering, Physics
- Master Thesis, Semester Project