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Spontaneous polarization plays a crucial role in manifesting unprecedented properties in polar materials, yet its mechanism remains relatively unexplored. We lack certainty regarding how asymmetric groups distort to generate spontaneous polarization, and the understanding of how spontaneous polarization changes with temperature is incomplete. In this study, we have grown a high-quality crystal of metal borate halides, specifically Mn3B7O13Cl, as a proof of principle for spontaneous polarization in polar materials. Our results for Mn3B7O13Cl indicate that approximately 80% of spontaneous polarization originates from [MnCl2O4], and the magnitude of spontaneous polarization associated with [MnCl2O4] remains nearly constant with temperature. Meanwhile, the temperature-dependent variation in spontaneous polarization is entirely governed by the [BO4–BO3] groups. These findings provide insight into the mechanism of spontaneous polarization in polar materials, particularly metal borate halides, and offer a new pathway for inducing properties related to spontaneous polarization in this class of materials. [ABSTRACT FROM AUTHOR]

Achieving both high efficiency and long-term stability is the key to the commercialization of perovskite solar cells (PSCs)1,2. However, the diversity of perovskite (ABX3) compositions and phases makes it challenging to fabricate high-quality films3–5. Perovskite formation relies on the reaction between AX and BX2, whereas most conventional methods for film-growth regulation are based solely on the interaction with the BX2 component. Herein, we demonstrate an alternative approach to modulate reaction kinetics by anion–π interaction between AX and hexafluorobenzene (HFB). Notably, these two approaches are independent but work together to establish ‘dual-site regulation’, which achieves a delicate control over the reaction between AX and BX2 without unwanted intermediates. The resultant formamidinium lead halides (FAPbI3) films exhibit fewer defects, redshifted absorption and high phase purity without detectable nanoscale δ phase. Consequently, we achieved PSCs with power conversion efficiency (PCE) up to 26.07% for a 0.08-cm2 device (25.8% certified) and 24.63% for a 1-cm2 device. The device also kept 94% of its initial PCE after maximum power point (MPP) tracking for 1,258 h under full-spectrum AM 1.5 G sunlight at 50 ± 5 °C. This method expands the range of chemical interactions that occur in perovskite precursors by exploring anion–π interactions and highlights the importance of the AX component as a new and effective working site to improved photovoltaic devices with high quality and phase purity.The use of anion–π interactions during perovskite film formation is shown to give better quality perovskite layers with high phase purity, leading to improved photovoltaic devices with high power conversion efficiency. [ABSTRACT FROM AUTHOR]

An efficient and environmentally benign procedure for the reactions of three components condensation of salicylaldehyde and two different CH acids to give 2-amino-4 H-chromenes catalyzed by a series of basic-functionalized ionic liquids was reported. The most possible reaction pathway was proposed for the first time by performing density functional theory (DFT) calculations. Both cation and anion of [Bmim]OH have a cooperative effect on the reaction. [Bmim]+ increases the electrophilicity of salicylaldehyde via intermolecular hydrogen bonds, while OH− deprives proton of two CH acids to strengthen their nucleophilic ability. [ABSTRACT FROM AUTHOR]

Elbaite is a natural silicate mineral with a spontaneous electric field. In the current study, it was selected as a pyroelectric catalyst to promote hydrogen peroxide (H2O2) for dye decomposition due to its pyro-electro-chemical coupling. The behaviors and efficiency of the elbaite/H2O2 system in rhodamine B (RhB) degradation were systematically investigated. The results indicate that the optimal effective degradability of RhB reaches 100.0% at 4.0 g/L elbaite, 7.0 mL/L H2O2, and pH = 2.0 in the elbaite/H2O2 system. The elbaite/H2O2 system exhibits high recyclability and stability after recycling three times, reaching 94.5% of the degradation rate. The mechanisms of RhB degradation clarified that the hydroxyl radical (·OH) is the main active specie involved in catalytic degradation in the elbaite/H2O2 system. Moreover, not only does elbaite act as a pyroelectric catalyst to activate H2O2 in order to generate the primary ·OH for subsequent advanced oxidation reactions, but it also has the role of a dye sorbent. The elbaite/H2O2 system shows excellent application potential for the degradation of RhB. [ABSTRACT FROM AUTHOR]