Lehrstuhl EP2 Uni Bayreuth

Mixed halide perovskites often undergo reversible phase segregation under illumination, yet the exact underlying mechanism and the material properties affecting this process remain unclear. By combining time-resolved photoluminescence (TRPL) with in situ X-ray diffraction (XRD) under illumination, we show that segregation kinetics and the thermodynamic limit of segregation under illumination in MAPbI1.5Br1.5 are not intrinsically linked. The segregation rate increases linearly with the defect density inferred from TRPL. In contrast, the equilibrium extent of segregation is independent of defect density but instead decreases with reducing crystallite size down to a critical, finite-size threshold of ∼40 nm, below which segregation is suppressed. Defect passivation using the ionic liquid BMIMBF4 slows the segregation kinetics but does not affect equilibrium limits. These findings establish crystallite size as a thermodynamic constraint and defects as kinetic mediators, outlining considerations for designing photostable mixed halide perovskites.

Green hydrogen is widely regarded as a key to a sustainable future, offering a clean and flexible fuel option for decarbonizing the energy, transport, and industrial sectors. While photocatalytic approaches are known for generating hydrogen directly from water, most existing methods require (over)stoichiometric amounts of sacrificial reagents, which is far from ideal for the production […]

Visible-light-mediated difunctionalization of nonactivated alkenes offers a sustainable and efficient strategy for constructing diverse molecular frameworks relevant to medicinal chemistry, polymer science, and synthesis of fine chemicals. While established approaches─such as photoredox catalysis, energy transfer (EnT), and ligand-to-metal charge transfer (LMCT)─have demonstrated success, they typically require external photocatalysts to achieve high reactivity. Alternatively, electron donor–acceptor […]