Charge carriers’ density, their lifetime, mobility, and the existence of trap states are strongly affected by the microscopic morphologies of perovskite films, and have a direct influence on the photovoltaic performance. Here, we report on micro-wrinkled perovskite layers to enhance photocarrier transport performances. By utilizing temperature-dependent miscibility of dimethyl sulfoxide with diethyl ether, the geometry of the microscopic wrinkles of the perovskite films are controlled. Wrinkling is pronounced as temperature of diethyl ether (TDE) decreases due to the compressive stress relaxation of the thin rigid film-capped viscoelastic layer. Time-correlated single-photon counting reveals longer carrier lifetime at the hill sites than at the valley sites. The wrinkled morphology formed at TDE = 5 °C shows higher power conversion efficiency (PCE) and better stability than the flat one formed at TDE = 30 °C. Interfacial and additive engineering improve further PCE to 23.02%. This study provides important insight into correlation between lattice strain and carrier properties in perovskite photovoltaics.

While solution-processed halide perovskite thin films caused enormous attention when used in solar cells, thick films prepared by compressing perovskite powders are considered promising candidates for the next generation of...

A cooperative spin transition and thin platelet formation is observed for 1D coordination polymers of amphiphilic iron(ii) spin crossover complexes.

While using additives such as ionic liquids (IL) is known to boost the efficiency and stability of perovskite solar cells, it is still unclear how ILs impact the difficile perovskite...

Within the last few years, applying pressure to improve and alter the structural and optoelectronic properties of halide perovskite thin films and powderbased thick-film pellets has emerged as a promising processing method. However, a detailed understanding of the relationship between perovskite microstructure, pressing process, and final film properties is still missing. Here, we investigate the impact of powder microstructure on the compaction processes during pressure treatment and on the final properties of powder-pressed thick films, using the model halide perovskite methylammonium lead iodide (MAPbI 3 ). Analyzing pressure relaxations together with XRD and SEM characterizations, we find that larger powder particles result in less compact thick films with higher surface roughness. Furthermore, larger particles exhibit stronger sintered connections between individual powder particles, resulting in less crushing and particle rearrangement but in more pronounced plastic deformation during pressure treatment. Moreover, plastic deformation of the powder particles leads to a reduction of crystallite size in the final film. This reduction results in increased nonradiative, defect-associated excited state recombination, as confirmed by photoluminescence investigations. More plastic deformation also deteriorates the grain boundary quality and consequently facilitates ion migration, which is reflected in higher electrical dark conductivities of the thick films. Thus, our work elucidates how important the design of the perovskite powder microstructure is for the pressure-induced compaction behavior and for the resulting structural, optical, and electrical thick-film properties. These insights will pave the way for tailored pressure processing of halide perovskite films with improved optoelectronic properties.

In recent years, record efficiencies of halide perovskite-based devices have been achieved by processing high-quality thin films, where small morphology differences seem to be relevant for optimized optoelectronic functionality. However, a detailed understanding on how small morphological changes in perovskite films affect their structural and optoelectronic properties is still missing. Here, we investigate the influence of small morphology differences (i.e., increased grain size and crystallographic orientation), which are induced by hot-pressing methylammonium lead iodide (MAPbI3) thin films, on the structural properties, phase transition behavior, energetic disorder, and defects. To this end, detailed temperature-dependent photoluminescence (PL) and absorption analyses from 300 K down to 5 K are performed. The morphology differences, confirmed by scanning electron microscopy and X-ray diffractometry analyses, result in an increased phase transition temperature for hot-pressed (HP) films, which we attribute to less strain. Moreover, fluence-dependent and transient PL measurements reveal a lower defect density in HP films. Here, besides grain size, also the degree of orientation appears to enhance the charge carrier lifetimes. The identified interdependence of strain and defect properties with film morphology suggests small differences in the perovskite’s energetic disorder. Our work thus emphasizes the importance that even small structural differences in halide perovskites have on their optoelectronic functionality, spurring their further optimization.

Abstract. We investigate experimentally the collective behavior of a wet granular monolayer under vertical vibrations. The spherical particles are partially wet such that there are short-ranged attractive interactions between adjacent particles. As the vibration strength increases, clustering, reorganizing and melting regimes are identified subsequently through a characterization with the bond-orientational order parameters and the mean kinetic energy of the particles. The melting transition is found to be a continuous process starting from the defects inside the crystal.

Here, we investigate in detail the impact of the size of the methylammonium iodide (MAI) reactants in the mechanochemical powder synthesis of the halide perovskite methylammonium lead iodide (MAPbI3). Morphology and structural characterizations by scanning electron microscopy and X‐ray diffraction reveal that with increasing MAI reactant size, the particle size of the perovskite powder increases, while its defect density decreases, as suggested by nuclear quadrupole resonance spectroscopy and photoluminescence investigations. The reason for this behavior seems to be associated to the sensitive influence of the MAI size on the time durations of MAPbI3 synthesis and delayed MAPbI3 crushing stage during ball milling. Thus, our results emphasize the high importance the reactant properties have on the mechanochemical synthesis of halide perovskites and will contribute to enhance the reproducibility and control of the fabrication of halide perovskites in powder form.