Lehrstuhl EP2 Uni Bayreuth

Quantum wells made of quasi two-dimensional organic–inorganic hybrid perovskites (2D-PKs) offer a high degree of flexibility in tailoring optoelectronic properties through carrier confinement and functional interlayers. Compared to their 3D counterparts, 2D-PKs exhibit tunable photoluminescence, excitonic binding at room temperature, and enhanced structural stability. However, the dynamics of photoinduced charge carriers and their transport properties […]

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 […]