Dr. Alexander Urban
Lehrstuhl für Photonik und Optoelektronik
Department für Physik und CeNS
Amalienstr. 54, D-80799 München, Germany
Organic/Inorganic halide perovskites have taken the scientific community by storm, with the most striking advances coming in the field of photovoltaics. Here, the external efficiency of perovskite cells has improved from under 4% to over 20% in just five years. However, this material has also shown promise in light-emitting applications such as LEDs and lasers. While most of the work carried out has been done on bulk perovskite, research on perovskite nanocrystals has lagged behind. I am interested in synthesizing perovskite nanocrystals, and using optical spectroscopy to characterize these and to gain insight into fundamental properties of this exciting material. Furthermore I wish to explore how the optical and electrical properties unique to these nanocrystals can be exploited for applications ranging from photon detection to photovoltaics and light emission.
I am engaged in developing new material systems for the efficient, cheap generation of light in the UV/blue range of the electromagnetic spectrum. To this end I am looking to fabricate fluorescent nanocrystals, understand the complex interplay between composition and optical properties and use this to improve and develop more efficient emitters. I am not only interested in the recently emerged organic/inorganic halide perovskites, but also in an equally novel material, carbon dots. These highly luminescent nanoparticles are easy to fabricate, non-toxic and show fascinating optical properties. The goal is to understand what imbues carbon dots with these properties and use this information in order to tune the optical emission as desired. Additional UV/blue emitting materials, such as ZnO, are also explored.
Metallic and metal-based nanoparticles and nanostructures feature localized plasmons, rendering their optical properties fascinating. These include a strong effect of geometry, size and material used, enhanced electromagnetic fields around nanoparticles and strong coupling both between individual plasmonic nanoparticles and between plasmonic nanoparticles and strong optical emitters. The electromagnetic fields can be exploited to greatly enhance absorption, fluorescence and Raman scattering, vastly improving the properties of various materials. Additionally, due to their large absorption and scattering cross sections, plasmonic nanoparticles interact strongly with light and can be trapped, guided and printed onto surfaces depending on the interplay of plasmonic material, laser wavelength, and surrounding material.