To explore the differences in the nutritional quality of the muscles of bighead carp from different environments and aquaculture systems, we investigated three types of water bodies typically used for aquaculture: A common culture pond (NC), a natural lake (PY), and a cold water reservoir (XHK). Parameters affecting quality were evaluated, including muscle microstructure, fatty acid profiles, amino acid profiles, and volatile compounds. Fish from the XHK reservoir had the smallest muscle fiber diameter and the highest muscle fiber density (25.3 fibers/0.01 mm 2 ), while muscle fiber density was lowest in fish from the NC pond (9.7 fibers/0.01 mm 2 ). The bighead carp from the XHK reservoir had a much wider variety of unsaturated fatty acids, as well as higher levels of total polyunsaturated fatty acids. Eicosapentaenoic acid (EPA), docosahexenoic acid (DHA), and arachidonic acid (AA) were all significantly more abundant in the XHK group, increases of 7.48%, 12.12%, and 17.49%, respectively ( P < 0.05). The bighead carp from NC contained more “fishy” volatile flavor substances, as well as hydrocarbons with higher threshold values. Fish from XHK and NC had a greater umami intensity due to the presence of abundant volatiles with special aromas, including 1-Octene-3ol, DL-Menthol, and 2-ethyl-.

Combining two-dimensional (2D) perovskites with other 2D materials to form a van der Waals (vdW) heterostructure has emerged as an intriguing way of designing electronic and optoelectronic devices. The structural, electronic, and optical properties of the 2D (PEA) 2 PbI 4 /black phosphorus (BP) [PEA:(C 4 H 9 NH 3 ) + ] vdW heterostructure have been investigated using first-principles calculations. We found that the (PEA) 2 PbI 4 /BP heterostructure shows a high stability at room temperature. It is demonstrated that the (PEA) 2 PbI 4 /BP heterostructure exhibits a type-I band arrangement with high carrier mobility. Moreover, the band gap and band offset of (PEA) 2 PbI 4 /BP can be effectively modulated by an external electric field, and a transition from semiconductor to metal is observed. The band edges of (PEA) 2 PbI 4 and BP in the (PEA) 2 PbI 4 /BP heterostructure, which show significant changes with the external electric field, provide further support. Furthermore, the BP layers can enhance the light absorption of the (PEA) 2 PbI 4 /BP heterostructures. Our results indicate that the 2D perovskite and BP vdW heterostructures are competitive candidates for the application of low-dimensional photovoltaic and optoelectronic devices.

It is generally known that lead halide perovskite films used in solar cell devices inevitably introduce defects during solution-based growth at near room temperature. In all defects, the halide anion and organic cation vacancies are ubiquitous, facilitating ion diffusion and leading to the decomposition of thin films at the surface and grain boundaries. Studies have shown that fluoride can be introduced into the film and the strong electronegativity of fluorine can be used to passivate the point vacancies. In this study, the first-principles method based on density functional theory is used to investigate the introduction of superhalogen BF 4 anions on the surface of the FAPbI 3 perovskite film, which is more electronegative than fluoride. By using the strong electronegativity of BF 4 to strengthen the chemical bond with the Pb atom and combine with organic cations, it can effectively passivate the I atom vacancy and improve the formation energy of the formamidinium (FA) vacancy, thereby inhibiting the formation of FA vacancies. This approach provides a feasible way to prepare high-stability perovskite solar cells.

Organic–inorganic hybrid perovskites have become the most promising materials for the next generation of solar cells. However, the low thermal and chemical stability of these materials represented by CH3NH3PbI3 is the most challenging issue, which ultimately affects the durability of devices. Therefore, to fundamentally improve the stability of perovskite solar cells, we need to explore more stable organic–inorganic perovskite materials. Using superlattice structures is an attractive strategy to expand the perovskite family and obtain excellent optoelectronic materials. The stability and photoelectric properties of hybrid perovskites can be improved by introducing a functional diamino cation. Therefore, the superlattice structure, thermodynamic stability, electronic properties, exciton properties, power conversion efficiency, and optical absorption properties of (CsPbI3) n /PDAPbI4 (n = 1–4) and (MAPbI3) n /PDAPbI4 (n = 1–4) hybrid perovskites are calculated using the first-principles method based on density functional theory. The PDA in the superlattices is p-phenylenediamine. The results show that these superlattices show good thermodynamic stability, and these superlattices have direct band gaps and are tunable, with small effective masses of electrons and holes. By increasing the coupling effect between Pb–I inorganic layers, diamino organic cations become more conducive to the carrier migration between Pb–I inorganic layers. The charge densities of the maximum valence band state and the minimum conduction band state are distributed in different regions of the superlattice. It is shown that (MAPbI3) n /PDAPbI4 (n = 3 and 4) structures are type II superlattices and the recombination rate of electron–hole pairs is greatly reduced. These superlattices have good optical absorption characteristics and high absorption coefficients in the range of solar radiation, which can provide theoretical support for obtaining stable and efficient perovskite optoelectronic devices. The power conversion efficiencies of single-junction solar cells based on (CsPbI3)4/PDAPbI4 and (MAPbI3)4/PDAPbI4 perovskites are 22.87 and 21.02%, respectively.

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