Photocatalytic CO2 reduction is an appealing approach to convert solar energy into high value-added chemicals. All-inorganic CsPbBr3 quantum dots (QDs) have emerged as a promising photocatalyst for reducing CO2. However, pristine CsPbBr3 has a low catalytic performance, mainly due to severe charge recombination. Herein, a 0D/2D heterojunction of CsPbBr3 QDs/Bi2WO6 nanosheet (CPB/BWO) photocatalysts is fabricated for photocatalytic CO2 reduction. The CPB/BWO photocatalyst achieves excellent photocatalytic performance: the total yield of CH4/CO is 503 μmol g–1, nearly 9.5 times higher than the pristine CsPbBr3. The CPB/BWO heterojunction also exhibits much-improved stability during photocatalytic reactions. On the basis of various characterization techniques, our investigations verified a direct Z-scheme charge migration mechanism between CsPbBr3 QDs and Bi2WO6 nanosheets. The improved photocatalytic performance is originated from the high spatial separation of photoexcited charge carriers in CPB/BWO, which can also preserve strong individual redox abilities of two components. This work reports an efficient direct Z-scheme heterojunction photocatalytic system based on metal halide perovskites. The novel strategy we proposed may bring up new opportunities for the development of metal halide perovskite photocatalysts with greatly enhanced activities.

Single-phase homogeneous (Na0.2Bi0.2Ba0.2Sr0.2Ca0.2)TiO3 powder with high configurational entropy was synthesized by using a solid-state method. Calculations of thermodynamic parameters and related experiments indicate that both entropy and enthalpy drive the formation of a stable system. To further research the material's performance, we sintered the powder into a ceramic, which exhibited relaxation behavior because of the disorder of the microscopic composition. In addition, an applied electric field of 145 kV/cm produces a discharge energy density of 1.02 J/cm3. Meanwhile, the adiabatic temperature is 0.63 K at 60 kV/cm. These properties suggest that the electrocaloric effect of the (Na0.2Bi0.2Ba0.2Sr0.2Ca0.2)TiO3 ceramic is attractive for applications such as solid-state refrigeration and energy storage. High-entropy perovskite oxides are also highly tolerant to ions, and their properties can be tailored by tuning their composition, making them attractive for a broad range of applications.

Converting CO2 into chemical fuels with sunlight is a very attractive approach to solve the greenhouse effect and fossil fuel crisis. Metal halide perovskite nanocrystals (NCs) have been identified as ideal semiconductor photocatalysts for photocatalytic CO2 reduction due to their unique properties, such as strong light absorption, low exciton binding energy, tunable bandgaps, and low cost. However, the pristine perovskite NCs suffering from inevitable defects, which lower their charge transfer efficiency and are detrimental to photocatalytic performance toward CO2 reduction. Herein, a facile approach to modify the surface defects of CsPbBr3 NC is demonstrated using tetrafluoroborate salts as defects treatment agent and loading Co2+ as a cocatalyst. As a result, the optimized Co2+ on the surface of defect‐free CsPbBr3‐BF4 shows a remarkable photocatalytic CO2 activity of 83.8 μmol g−1 h−1, which indicates that the surface modification can effectively suppress the undesired charge recombination in CsPbBr3 NC and promote its charge separation efficiency. This work provides an effective method to modify the surface defects of the CsPbBr3 NCs for high efficient photocatalytic CO2 reduction and broadens the photocatalytic applications of halide perovskites.

Defects in perovskite layers usually cause nonradiative recombination, impairing device performance and stability. Here, fluoroethylamine (FC2H4NH3, FEA) is integrated into the perovskite film to passivate defects. By engineering of different amounts of fluorine in the molecule, it is found that when 2‐fluoroethylamine (1FEA), in which one F bonds to the first carbon atom at the end of the molecule's structure, is used, the F atoms appear to be distributed throughout the bulk to the very surface. When 2,2‐difluoroethylamine (2FEA) and 2, 2, 2‐trifluoroethylamine (3FEA) are used, F is prone to distribution in the bulk of the perovskite film, while there appears to be no detectable F content on the surface. With the FEA passivation, the nonradiative recombination is suppressed, the carrier‐lifetime is improved to 840.01 ns, and the film‐air interface offers greater hydrophobicity, especially in the case of 1FEA, where because it is distributed throughout the film thickness, it passivates more defects and delivers the highest efficiency, as much as 23.40%. The device with 3FEA shows the best environmental stability; specifically, the bare cell without any encapsulation maintains 87% of its initial efficiency after exposure to the ambient environment for 1200 h.

optical absorption coefficient, [1] high carrier mobility, [2] low exciton binding energy, [3] long carrier diffusion length, [4] adjustable bandgap, [5] and low manufac turing cost. [6] To date, the certified photo electric conversion efficiency (PCE) for perovskite solar cells (PSCs) has reached 25.5%, [7] which makes PSCs a strong future competitor in the photovoltaic industry. FAPbI 3 has been widely used as the light absorber for singlejunction PSCs due to its narrower bandgap and higher Shockley-Queisser limit efficiency compared with MAPbI 3 . [8] However, the perovskite devices based on FAPbI 3 poly crystalline films face the problem of phase and environmental instability. [9] The black α phase easily transforms to the yellow δ phase, which destroys the optoelectronic properties. [10] The phase instabilities are accelerated by the poor quality of the perovskite polycrystalline film, which is closely correlated with the crystallization process. [11] At present, rapid crystallization by the mostused solution method with N,Ndimethylformamide (DMF) or dime thyl sulfoxide (DMSO) solvent will inevi tably lead to the formation of a solution-complex intermediate phase, such as FAI-PbI 2 -DMSO, in the perovskite crystalliza tion process. [12] However, the final product will not be pure and stable αFAPbI 3 after the process of hightemperature annealing With its power conversion efficiency surpassing those of all other thin-film solar cells only a few years after its invention, the perovskite solar cell has become a superstar. Controlling the intermediate phase of crystallization is a key to obtaining high-quality perovskite films. Herein, a single molecule additive, N,N-dimethylimidodicarbonimidic diamide hydroiodide (DIAI), is incorporated into the perovskite precursor to eliminate the influence of intermediate phases. By taking advantage of the interaction of DIAI and dimethyl sulfoxide (DMSO), the intermediate phase FAI-PbI 2 -DMSO complex is eliminated, and δ-FAPbI 3 is entirely converted to the desired α-FAPbI 3 during the crystallization step, resulting in enlarged grain size and improved crystalline quality. This is the first observation in the solution method that FAPbI 3 can be obtained without an intermediate phase for high-performance perovskite solar cells. Furthermore, DIAI is effective at passivating surface defects, resulting in reduced defect density, increased carrier lifetime, and improved device efficiency and stability. The champion device achieves an efficiency of 24.13%. Furthermore, the bare device without any encapsulation maintains 94.1% of its initial efficiency after ambient exposure over 1000h. This work contributes a strategy of synergistic crystallization and passivation to directly form α-FAPbI 3 from the precursor solution without the influence of intermediate impurities for high-performance perovskite applications.