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Concerning the study of flexible piezoelectric devices, both scholars and engineers propose that poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) shows more merits than oriented polyvinylidene fluoride (OPVDF) in terms of dielectric, piezoelectric, mechanic–electric, acoustic emission reception performances, etc. Thus, in this study, to clarify the differences between the two types of polymers on their ferroelectric and piezoelectric behaviors, we systematically investigated samples to analyze their molecular structures and phase structures, and to compare their dielectric properties and acoustic emission reception performances. It was found that the wedge effect of TrFE, P(VDF-TrFE), possesses higher regular β phase crystal grains, which are easier to order along the electric field and possess more ordered static charge distribution than that of OPVDF. Consequently, a considerable saturated electric polarization (Pm ∼ 15 μC cm−2 under 225 MV m−1), a large piezoelectric coefficient (d33 ∼ −21.5 pC N−1) and a low coercive electric field (Ec ∼ 50 MV m−1) were obtained in the P(VDF-TrFE) films. It is worth noting that P(VDF-TrFE) shows a more stable d33 piezoelectric response (up to 120 °C) than that of the OPVDF. Additionally, the P(VDF-TrFE) piezoelectric films exhibit a sensitive acoustic emission reception property at approximately 70 dB and an extensive response frequency range from 10 to 100 kHz. These combined properties demonstrate that P(VDF-TrFE) piezoelectric films are a promising material for flexible and easily shaped electronic devices, including hydroacoustic sensors, actuators, and energy transfer units. [ABSTRACT FROM AUTHOR]

Recent years have witnessed a significant performance breakthrough in all-inorganic perovskite solar cells, but their power conversion efficiencies are still far lower than the theoretical limit and they also suffer from severe moisture instability. Based on the discussions on crystal structures, chemical bonds, and optical and electrical properties of all-inorganic perovskites, we have summarized their comprehensive applications in solar cells and detectors. The effects of monovalent and divalent ion doping, morphology, crystallization control and interface engineering on device performance and stability have been carefully evaluated. A narrow-bandgap CsPbI3 polycrystalline bulk film solar cell has achieved the highest power conversion efficiency of 18.4%, while a stable CsPbBr3 nanocrystal film is a more successful choice in UV-visible and high-energy ray detections. Finally, we call on boosting the performance and stability of solar cells and shortening the response time for tandem photovoltaic and high-speed dynamic detection applications, respectively. [ABSTRACT FROM AUTHOR]

Silver niobate (AgNbO3)-based dielectric materials show great application potential in pulse power energy storage systems due to their high energy storage density. However, a fundamental understanding of this important lead-free system has remained controversial ever since its discovery in 1958. In the present study, a comprehensive investigation was performed via analyzing the chemical structure and physical properties of AgNbO3-based dielectric materials. The results confirm that the dielectric anomalous behavior occurring at ∼170 °C, which has been considered as the freezing temperature/transition of the antipolar dipoles (Tf) in early publications, actually originates from a phase transition between the non-centrosymmetric weakly polar and centrosymmetric non-polar phases. Moreover, the weakly polar phase exhibiting antipolar ordered behavior is proposed to be ferrielectric and is responsible for the strong field-induced double-like polarization hysteresis. The dielectric relaxor behavior at ∼70 °C, which was attributed to the M1 ↔ M2 transition in early studies, was further demonstrated to be intimately correlated with the presence of local ferroelectric-type polar domains in a weakly polar/ferrielectric phase. The observed weak remnant polarization within double-like polarization hysteresis under strong field cycles is proposed to mainly originate from the polarization contributed by the residual strong field-induced ferroelectric phase. [ABSTRACT FROM AUTHOR]