[en] TiO₂ films with controlled macroporous structures have been prepared from the precursor solution containing photo monomer pentaerythritol tetraacrylate by a photo polymerization-induced phase separation method (PIPS) in the absence of any surfactant and colloidal templates. The gel TiO₂ film deposited from the precursor solution by dip-coating was irradiated with ultraviolet light for some time. During the irradiation process, the polymerization of the photo monomer was induced, which resulted in the phase separation in the film system. After the reaction, two phases existed in the film, one was the emerging polymer rich phase, another was the residual monomer-TiO₂ oligomer rich phase. After heat-treatment at 600 ^oC, the entire polymer decomposed and a well-defined interconnected macroporous TiO₂ films could be obtained. X-ray diffraction, scanning electron microscopy, atomic force microscopy, thermogravimetric and differential thermal analysis were used to characterize the macroporous TiO₂ films. The results showed that the macroporous texture could be tuned by changing the composition of the precursor solution. The solvent evaporation was controlled by the addition of polyvinylpyrrolidone. Highly macroporous TiO₂ films prepared by the PIPS method exhibited much higher photocatalytic activity for the decomposition of methylene blue dye than the dense TiO₂ film.

[en] The microscopic stripe pillar is one of the most frequently adopted building blocks for hydrophobic substrates. However, at high temperatures the particles on the droplet surface readily evaporate and re-condense on the pillar sidewall, which makes the droplet highly unstable and undermines the overall hydrophobic performance of the pillar. In this work, molecular dynamics (MD) simulation of the simple liquid at a single stripe pillar edge defect is performed to characterize the droplet’s critical wetting properties considering the evaporation–condensation effect. From the simulation results, the droplets slide down from the edge defect with a volume smaller than the critical value, which is attributed to the existence of the wetting layer on the stripe pillar sidewall. Besides, the analytical study of the pillar sidewall and wetting layer potential field distribution manifests the relation between the simulation parameters and the degree of the droplet pre-wetting, which agrees well with the MD simulation results. (paper)

[en] A simplified analytical model of single-level quantum dot (QD) refrigerator was studied without considering the electron spin and Coulomb interaction. Based on the ballistic transport of electrons between two reservoirs across the QD, the Joule heat of the system was assumed to be generated from the Ohmic contacts between the QD and reservoirs. By using the transition rate equation, the performance of the QD refrigerator was studied with respect to the electron transmission probability and the partition ratio (i.e. the fraction of Joule heat generated in the system that releases into the cold reservoir). The analytical expression of the maximum coefficient of performance (COP) was obtained under the exoreversible working condition. The Carnot-bound-dependent COP at maximum cooling power of the QD system was also demonstrated numerically. The results of this work may provide some guidance for the design of mesoscopic refrigerators. (paper)

[en] Highlights: • Utilizing Ag nanoparticles in the photodetectors based on CH₃NH₃PbI₃ perovskite films. • Different effects of Ag nanoparticles in the two CH₃NH₃PbI₃ perovskite photodetectors prepared using different precursors. • Enhanced performances of photodetectors synthesized from PbCl₂ and CH₃NH₃I by using Ag-nanoparticles-coated substrates. -- Abstract: Au and Ag nanoparticles (NPs) are often applied in inorganic and polymer photodetectors to enhance light-harvesting ability. Au NPs have been used in perovskite photodetectors and have shown good performance. The application of Ag NPs in perovskite photodetectors has not been previously reported. In this report, Ag NPs prepared by thermal evaporation deposition were introduced into CH₃NH₃PbI₃ perovskite photodetectors. The perovskite films were prepared using two kinds of precursor solutions. The morphology and crystallinity of the perovskite films changed greatly upon introducing Ag NPs. The performances of photodetectors based on the two kinds of perovskite films also changed when introducing Ag NPs. For the perovskite photodetector prepared from PbI₂ and methylammonium iodide, the responsivity decreased from 6.14 mA/W to 3.18 mA/W and the detectivity decreased from 2.68 × 10¹⁰ Jones to 1.21 × 10¹⁰ Jones, upon introducing Ag NPs. This was due to a less favorable film morphology and lower crystallinity when introducing Ag NPs. When PbI₂ in the precursor solution was replaced with PbCl₂, the device with Ag NPs had a higher responsivity, and a faster response time. The responsivity was 7.00 mA/W, which was four times higher than that of the device without Ag NPs. The detectivity of the device increased from 1.91 × 10¹⁰ Jones to 3.39 × 10¹⁰ Jones upon introducing Ag NPs.

[en] Efficient manipulation of crystallization and control over defects are crucial for optimizing the performance and durability of perovskite solar cells (PSCs). In this study, a novel organic multifunctional additive, 2-(furan-3-yl)ethanamine hydrochloride (FFEACl), is introduced which plays a pivotal role in regulating the crystallization process of FAPbI${}_3$. Incorporating FFEACl into the perovskite precursor solution effectively suppresses the formation of undesirable non-perovskite phase impurities while promoting the oriented crystallization of the $\mathrm{\alpha <!--\; ??\; -->}$-phase FAPbI${}_3$. Moreover, the addition of FFEACl leads to a more uniform surface potential and reduced defect density in the resulting FAPbI${}_3$ film. Consequently, the top-performing PSC exhibits an impressive power conversion efficiency (PCE) of 25.41%, along with enhanced operational stability. Notably, the fabricated PSCs maintain over 80% of their initial PCE even after 1000 h of continuous operation under one-sun illumination. The findings present a facile and effective strategy for fabricating perovskite photovoltaic devices with exceptional performance and long-term reliability. (© 2024 Wiley‐VCH GmbH)

[en] Multilevel porous ZnO nanosheets have been synthesized from the precursor solution containing monomer and photoinitiator by a photopolymerization method in water-in-oil (W/O) microemulsion, avoiding the introduction of a template. The radical-mediated photopolymerization is a cross-linking polymerization process induced by the UV light to motivate the photoinitiator from the ground state to the excited state, which makes it possible to realize the rapid transformation of liquid monomers into solid polymer. After calcination to remove the solid polymer, pierced ZnO nanosheets show a well-defined interconnected architecture with large specific surface area and various pore sizes from mesopores to macropores. Additionally, the morphology and size of pores can be adjusted by changing the components of W/O microemulsion. Merited by the unique porous structure and high specific surface area, the pierced ZnO nanosheets demonstrate intended performance as an anode of lithium ion batteries. Moreover, this strategy is a well-designed and attractive method for producing other porous nanomaterials.

[en] Highlights: • Modifying solution-processed C₆₀-based ETL with a solid-state ionic-liquid in perovskite solar cell. • An efficiency of 15.09% shown in the solar cell with structure of FTO/IL/C₆₀/CH₃NH₃PbI₃/Sprio/Au. • Enhanced wettability and electron extraction exhibited in the IL/C₆₀ electron transport layers. -- Abstract: Low temperature solution-processed C₆₀ exhibits favorable electron mobility and band alignment, thus it is widely used to modify the interfaces between perovskite film and electron transport layer (ETL) in n-i-p planar heterojunction perovskite solar cells (PSCs). However, when C₆₀ was used as an independent ETL, PSCs exhibit poor performance. Herein, We have modified solution-processed C₆₀-based ETL with a solid-state ionic-liquid (1-ethyl-3-methylimidazolium iodide ([EMIM]I)). Using this interfacial modification method, we fabricated n-i-p planar heterojunction PSCs with optimized power conversion efficiency (PCE) of 15.09%, which was superior to that of PSCs based on unmodified C₆₀ ETL layer (12.11%). This work describes a novel method for low-temperature processing of efficient n-i-p PSCs.

[en] Organo-metal halide perovskite solar cells based on planar architecture have been reported to achieve remarkably high power conversion efficiency (PCE, >16%), rendering them highly competitive to the conventional silicon based solar cells. A thorough understanding of the role of each component in solar cells and their effects as a whole is still required for further improvement in PCE. In this work, the planar heterojunction-based perovskite solar cells were simulated with the program AMPS (analysis of microelectronic and photonic structures)-1D. Simulation results revealed a great dependence of PCE on the thickness and defect density of the perovskite layer. Meanwhile, parameters including the work function of the back contact as well as the hole mobility and acceptor density in hole transport materials were identified to significantly influence the performance of the device. Strikingly, an efficiency over 20% was obtained under the moderate simulation conditions.

[en] Highlights: • The planar n-i-p structure Br-PSCs were obtained at room temperature. • Ionic-liquids/C₆₀ bilayer were used as the ETL in planar n-i-p structure Br-PSCs. • The IL/C₆₀-based solar cells achieved the PCE of 5.88%. -- Abstract: A room temperature solution processed ionic liquids (1-benzyl-3-methylimidazolium chloride)/C₆₀ bilayer were used as the electron transport layer in planar n-i-p structure CH₃NH₃PbBr₃ perovskite solar cells. The ionic liquids could effectively decrease the work function and improve the wettability of the perovskite precursor solution on the C₆₀ layer. Moreover, C₆₀ guarantees the excellent electron mobility. In comparison with devices with different ETLs, the IL/C₆₀-based solar cells show greatly improved performance, achieving the PCE of 5.88% with a J_sc of 6.14 mA/cm², a V_oc of 1.39 V, and a FF of 69.94%.

[en] Highlights: • The eXtreme Gradient Boosting Regression (XGBR) algorithm was first applied to build a robust and predictive machine learning (ML) model for perovskite materials. • The method of combining machine learning and DFT calculation used in this article can greatly save computing resources and time, and accelerate the discovery of renewable energy materials. • Two lead-free perovskite structures screened out by the combination of machine learning and DFT calculation have reasonable band gap values, high environmental stability and good optical absorption properties. To accelerate the application of perovskite materials in photovoltaic solar cells, developing novel lead-free perovskite materials with suitable band gaps and high stability is vital. However, laborious experiment and density functional theory (DFT) calculation are time-consuming and incapable to screen promising perovskites rapidly and efficiently. Here, we proposed a novel search strategy combining machine learning and DFT calculation to screen 5,796 inorganic double perovskites. The eXtreme Gradient Boosting Regression (XGBR) algorithm was first applied to build a robust and predictive machine learning (ML) model for perovskite materials. XGBR algorithm yielded a lower mean square error (MSE) than both Artificial Neural Network (ANN) algorithm and Support Vector Regression (SVR) algorithm. From the ML model, two novel lead-free inorganic double perovskites: Na₂MgMnI₆, K₂NaInI₆, were obtained, suitable direct bandgaps of 1.46 eV for K₂NaInI₆ and 1.89 eV for Na₂MgMnI₆, which are similar to the organic–inorganic perovskite (MAPI3) CH₃NH₃PbI₃ (E_g = 1.6 eV), high thermal stability and good optical properties were also confirmed by DFT calculation. The method of combining ML and DFT exhibits high accuracy and significantly speeds up the discovery of promising perovskite materials.