Lead halide perovskites form the basis of a promising new technology in the field of photovoltaics. The efficiency of thin-film solar cells made from these materials has rocketed to > 22% within only a few years of research. Despite this rapid progress, a number of questions regarding the basic properties of lead halide perovskites remain open.
Lead halide perovskites are complex ionic crystalline materials, since they contain both heavy elements and typically also organic components. They are mechanically soft, and atomic rearrangements can efficiently be induced by thermal or optical excitation. The resulting structural fluctuations modify the local electronic structure and affect the charge transport. Significant spin polarizations have been predicted to emerge.
We track the dynamics in the system using a combination of photoemission techniques, optical spectroscopy, and transport measurements. We put a focus on the (dynamical) electronic structure and especially on the possibility to generate an electronic spin polarization in lead halide perovskites by optical excitation. The goal of this research is to help develop a full description of the microscopic mechanisms in solar cells made from perovskites and related materials. The experiments are carried out in close collaboration with our partners at the University of Erlangen-Nürnberg.