The electromechanical coupling in ferroelectric materials is controlled by several coexisting structural phenomena which can include piezoelectric lattice strain, 180° and non‐180° domain wall motion, and interphase boundary motion. The structural mechanisms that contribute to electromechanical coupling have not been readily measured in the past, particularly under the low‐to‐medium driving electric field amplitudes at which many piezoelectric materials are used. In this feature, results from in situ, high‐energy, and time‐resolved X‐ray diffraction experiments are interpreted together with macroscopic piezoelectric coefficient measurements in order to better understand the contribution of these mechanisms to the electromechanical coupling of polycrystalline ferroelectric materials. The compositions investigated include 2 mol% La‐doped PbZr0.60Ti0.40O3, 2 mol% La‐doped PbZr0.52Ti0.48O3, 2 mol% La‐doped PbZr0.40Ti0.60O3, undoped PbZr0.52Ti0.48O3, and 2 mol% Fe‐doped PbZr0.47Ti0.53O3. In all compositions, a strong correlation is found between the field‐amplitude‐dependence of the macroscopic piezoelectric coefficient and the contribution of non‐180° domain wall motion determined from the diffraction data. The results show directly that the Rayleigh‐like behavior of d33 piezoelectric coefficient is predominantly due to a Rayleigh‐like behavior of non‐180° domain wall motion. Furthermore, after separating contributions from lattice (atomic level) and domain wall motion (nanoscale level) to the measured macroscopic piezoelectric properties, we show that previously ignored intergranular interactions (microscopic level) account for a surprisingly large portion of the electromechanical coupling. These results demonstrate that electromechanical coupling in polycrystalline aggregates is substantially different from that observed in single crystalline materials. The construct of emergence is used to describe how averaged macrolevel phenomena are different from the material response observed in an isolated subcomponent of the material. Consequently, and due to its size‐scale complexity, the description of grain‐to‐grain interactions is presently inaccessible in most ab initio and phenomenological approaches. Results presented here demonstrate the need to account for these interactions in order to completely describe macroscopic electromechanical properties of polycrystalline materials.

A high‐efficiency solution‐processed inverted perovskite solar cell with poly[N,N′‐bis(4‐butylphenyl)‐N,N′‐bis(phenyl)benzidine] (poly‐TPD) as the hole transport layer is demonstrated. The perovskite forms large crystallites on poly‐TPD, yielding devices with an average power conversion efficiency of 13.8% and a maximum of 15.3%.

Guided by predictive discovery framework, we investigate bismuth triiodide (BiI3) as a candidate thin-film photovoltaic (PV) absorber. BiI3 was chosen for its optical properties and the potential for "defect-tolerant" charge transport properties, which we test experimentally by measuring optical absorption and recombination lifetimes. We synthesize phase-pure BiI3 thin films by physical vapor transport and solution processing and single-crystals by an electrodynamic gradient vertical Bridgman method. The bandgap of these materials is ∼1.8 eV, and they demonstrate room-temperature band-edge photoluminescence. We measure monoexponential recombination lifetimes in the range of 180-240 ps for thin films, and longer, multiexponential dynamics for single crystals, with time constants up to 1.3 to 1.5 ns. We discuss the outstanding challenges to developing BiI3 PVs, including mechanical and electrical properties, which can also inform future selection of candidate PV absorbers.

During the last years, several groups across the world have concentrated on the adaptation and further development of electrospinning (e-spinning) to enable ceramic fiber synthesis. Thus far, more than 20 ceramic systems have been synthesized as micro-and nanofibers. These fibers can be amorphous, polycrystalline, dense, porous, or hollow. This article reviews the experimental and theoretical basis of ceramic e-spinning. Furthermore, it introduces an expanded electro hydrodynamic (EHD) theory that allows the prediction of fired fiber diameter for lanthanum cuprate fibers. It is hypothesized that this expanded EHD theory is applicable to most ceramic e-spinning systems. Furthermore, electroceramic nanofibers produced via espinning are presented in detail along with an overview of electrospun ceramic fibers. J ournal

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