From Spin Dynamics of Charge Carriers to Fundamental Insights into The Band Structure of Lead Halide Perovskites

The emerging field of lead halide perovskite semiconductors offers a plethora of promising material compositions for applications. Experimentally exploring all of these combinations is challenging, especially in light of the increasing number of tandem devices. Theoretical models help predict suitable candidates, but require a fundamental understanding of the perovskite band structure. This is where our experimental methods come into play. Experimental spin physics helps improve, validate, and substantiate these models and provides insight into the underlying physics. The experimental method uses the optically oriented spin property of resident and photoexcited charge carriers as a probe. A strong and distinct charge carrier spin signal, typically the electron and hole spin simultaneously, can be observed and its spin precession resolved in time. The spin dynamics of the charge carriers is in the ns range and allows intense studies in different directions. The spin reveals the pronounced interactions between the charge carriers and their environment and is sensitive to band mixing, allowing, for example, the determination of the importance of distant bands as well as the study of the effective mass of the charge carriers. The methodological tools include time-resolved pump-probe Kerr spectroscopy, spin-flip Raman scattering, and optical orientation, which we have successfully applied to macroscopic perovskite crystals, nanocrystals, and 2D films.