Mixed cation perovskites currently achieve very promising efficiency and operational stability when used as the active semiconductor in thin‐film photovoltaic devices. However, an in‐depth understanding of the structural and photophysical properties that drive this enhanced performance is still lacking. Here the prototypical mixed‐cation mixed‐halide perovskite (FAPbI3)0.85(MAPbBr3)0.15 is explored, and temperature‐dependent X‐ray diffraction measurements that are correlated with steady state and time‐resolved photoluminescence data are presented. The measurements indicate that this material adopts a pseudocubic perovskite α phase at room temperature, with a transition to a pseudotetragonal β phase occurring at ≈260 K. It is found that the temperature dependence of the radiative recombination rates correlates with temperature‐dependent changes in the structural configuration, and observed phase transitions also mark changes in the gradient of the optical bandgap. The work illustrates that temperature‐dependent changes in the perovskite crystal structure alter the charge carrier recombination processes and photoluminescence properties within such hybrid organic–inorganic materials. The findings have significant implications for photovoltaic performance at different operating temperatures, as well as providing new insight on the effect of alloying cations and halides on the phase behavior of hybrid perovskite materials.

Perovskite-based solar cells (PSCs) have attracted attraction in the photovoltaic community since their inception in 2009. To optimize the performance of hybrid perovskite cells, a primary and crucial strategy is to unravel the dominant charge transport mechanisms and interfacial properties of the contact materials. This study focused on the charge transfer process and interfacial recombination within the n–i–p architecture of solar cell devices. The motivation for this paper was to investigate the impacts of recombination mechanisms that exist within the interface in order to quantify their effects on the cell performance and stability. To achieve our objectives, we firstly provided a rationale for the photoluminescence and UV-Vis measurements on perovskite thin film to allow for disentangling of different recombination pathways. Secondly, we used the ideality factor and impedance spectroscopy measurements to investigate the recombination mechanisms in the device. Our findings suggest that charge loss in PSCs is dependent mainly on the configuration of the cells and layer morphology, and hardly on the material preparation of the perovskite itself. This was deduced from individual analyses of the perovskite film and device, which suggest that major recombination most likely occur at the interface.

The influence of sputtered Pt 40 Pd 57 Al 3 thin films of varying thickness, in the as-deposited (AD) and annealed (AN) state, was investigated for the electro-oxidation of aqueous SO 2 . From physical characterisation (scanning electron microscopy (SEM) and grazing incidence X-ray diffraction (GIXRD)), significant differences were found in the morphology and crystallinity between AD and AN samples. In terms of electrochemical activity, the current output for the AD and AN thin films decreased as the thickness increased, whilst the AN thin films in general resulted in lower current outputs. No specific trend was observed for stability in an acidic environment and a 60 nm Pt 40 Pd 57 Al 3 thin film proved to be the optimum thickness for aqueous SO 2 electrooxidation. In addition, the 60 nm Pt 40 Pd 57 Al 3 AN thin film outperformed pure Pt (60 nm, AD and AN) in terms of current density and stability, emphasising the fact that multicomponent electrocatalysts can be superior compared with their pure metal counterparts.

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