Fabrication of Highly Transparent Superhydrophobic Coatings from Hollow Silica Nanoparticles

We herein report a simple and effective method to fabricate excellent transparent superhydrophobic coatings. 3-Aminopropytriethoxysilane (APTS)-modified hollow silica nanoparticle sols were dip-coated on slide glasses, followed by thermal annealing and chemical vapor deposition with 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (POTS). The largest water contact angle (WCA) of coating reached as high as 156° with a sliding angle (SA) of ≤2° and a maximum transmittance of 83.7%. The highest transmittance of coated slide glass reached as high as 92% with a WCA of 146° and an SA of ≤6°. A coating simultaneously showing both good transparency (90.2%) and superhydrophobicity (WCA: 150°, SA: 4°) was achieved through regulating the concentration of APTS and the withdrawing speed of dip-coating. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) were used to observe the morphology and structure of nanoparticles and coating surfaces. Optical properties were characterized by a UV–visible spectrophotometer. Surface wettability was studied by a contact angle/interface system. The effects of APTS concentration and the withdrawing speed of dip-coating were also discussed on the basis of experimental observations

Antifogging and Antireflection Coatings Fabricated by Integrating Solid and Mesoporous Silica Nanoparticles without Any Post-Treatments

Antifogging and -reflection coatings were fabricated on glass and poly­(methyl methacrylate) (PMMA) substrates by integrating solid silica nanoparticles of 25 nm (S-25) and mesoporous silica nanoparticles (MSNs) of 45 nm via layer-by-layer assembly without any post-treatments. Superhydrophilicity and a maximum transmittance of 98.5% in the visible spectral range was achieved for the (PDDA/S-25)₄/(PDDA/MSNs) coating deposited on slide glass. The maximum transmittance even reached as high as 99.3% in the visible spectral range by applying a coating of (PDDA/S-25)₈/(PDDA/MSNs) on PMMA substrate. Scanning and transmission electron microscopy were used to observe the morphology and structure of nanoparticles and coating surfaces. Optical properties were characterized by UV–visible spectrophotometer. Surface wettability was studied by a contact angle/interface system. The influence of mesopores was also discussed on the transmission and wetting properties of coatings. The high porosity of mesoporous nanoparticles and loose stacking of solid and mesoporous nanoparticles are considered to significantly contribute to the enhancements of both light transmission and hydrophilicity

Mechanically Robust, Thermally Stable, Broadband Antireflective, and Superhydrophobic Thin Films on Glass Substrates

In this study, we developed a simple and versatile strategy to fabricate hierarchically structured lotus-leaf-like superhydrophobic thin films. The thin films are broadband antireflective, and the average transmittance of coated glass substrates reached greater than 95% in the wavelength range of 530–1340 nm, in contrast to 92.0% for bare glass substrate. The thin film surface shows a static water contact angle of 162° and a sliding angle less than 4°. Moreover, the thin film is thermally stable up to 300 °C, and shows remarkable stability against strong acid, strong alkali, water drop impact, and sand impact abrasion, while retaining its superhydrophobicity. Further, the thin film can pass the 3H pencil hardness test. The current approach may open a new avenue to a variety of practical applications, including windshields, eyeglasses, windows of high rise buildings and solar cells, etc

Assessment for Anion-Exchange Reaction in CsPbX₃ (X = Cl, Br, I) Nanocrystals from Bond Strength of Inorganic Salt

Anion exchange via inorganic halide precursors is a highly efficient protocol to tune the chemical composition and optoelectronic properties of colloidal cesium lead halide perovskite (CsPbX3, X = Cl, Br, I) nanocrystals (NCs). However, a simple predication rule of precursors is lacking owing to limited understanding of these used halide compounds. Here, we first use the inorganic magnesium halide (MgX2) as a precursor to understand the halide exchange in CsPbBr3 NCs. The samples with Br– exchanged with Cl– or I– display a perfect preservation of cubic morphology, good stability, and high photoluminescence quantum yield. Then, by selecting a series of inorganic metal halide salts with different bond strength as precursors, we further find that the reaction exhibits thermal dynamic driving characteristics and the small energy difference in bonding strength between metal–X in halide salt and Pb–Br in CsPbBr3 NCs is advantageous for the anion exchange according to the vacancy diffusion mechanism. These findings illustrate an easy way to assess the feasibility of the anion-exchange reaction, significantly promoting the synthesis of compositionally diverse metal halide perovskite NCs with various optoelectronic properties

PEDOT:PSS/CuCl Composite Hole Transporting Layer for Enhancing the Performance of 2D Ruddlesden–Popper Perovskite Solar Cells

Poly­(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) is a popular hole transport layer (HTL) in 2D Ruddlesden–Popper (RP) perovskite solar cell (PSCs) due to its highly conductive, transparent, and solution-processable characteristics. However, fundamental questions such as its strong acidity or mismatched energy level with the 2D RP photoactive layer often restrict the performance and stability of devices. Herein, copper chloride (CuCl), a common direct band gap semiconductor, is doped into PEDOT:PSS, lowering the acidity and tuning the work function of PEDOT:PSS. Due to the improved wettability and the existing chloride in the PEDOT:PSS/CuCl composite substrate, the coated 2D perovskite films exhibit uniform morphology, vertically oriented crystal growth, and enhanced crystallinity. In comparison with controlled devices, the PEDOT:PSS/CuCl based inverted 2D RP PSCs show a maximum power conversion efficiency of 13.36% and long-term stability. The modified PEDOT:PSS overcomes intrinsic imperfections by doping CuCl, indicating that it has a lot of promise for mass production in electrical devices

Buried Interface Modification via Guanidine Thiocyanate for High-Performance Lead-Free Perovskite Solar Cells

Tin perovskites with exceptional optoelectronic properties have gained tremendous attention in environmentally friendly solar cells. However, it is still challenging to fabricate high-quality tin perovskite films with preferred crystal orientation and low interface defects by solvent engineering. Herein, a buried interface modification strategy (BIMS) is proposed to modify the interfaces between the hole transport layer and perovskite film. GA+ ions form tailored two-dimensional perovskites at the buried interface, inducing the template growth of Sn perovskite crystals with preferential orientation along the (100) plane. Moreover, the thiocyanate (SCN–) ions generate strong electrostatic attraction with uncoordinated Sn2+ ions, affecting its localized electron density around the buried interfaces and enhancing vacancy formation energy. As a result, the highest power conversion efficiency (PCE) of the perovskite solar cells (PSCs) via BIMS reaches up to 8.6%. Interestingly, the unencapsulated PSC remains at 80% of the initial PCE for 600 h after continuous 1 sun illumination at 55 °C under a nitrogen atmosphere. This study explicitly paves a novel and general strategy for developing high-performance lead-free PSCs

Dopamine Hydrochloride-Assisted Synergistic Modulation of Perovskite Crystallization and Sn²⁺ Oxidation for Efficient and Stable Lead-free Solar Cells

Tin perovskites have received great concern in solar cell research owing to their favorable optoelectronic performance and environmental friendliness. However, due to their poor crystallization and easy oxidation, the performance improvement for tin-based perovskite solar cells (TPSCs) is rather challenging. Herein, reductive 3-hydroxytyramine hydrochloride (DACl) with NH2·HCl and phenol groups as co-additives with SnF2 is added into the precursor to modulate perovskite crystallization and inhibit Sn2+ oxidation for high-performance TPSCs. The Lewis base group of NH2 HCl in DACl could bind to perovskite lattices to modulate the crystallization with suppressed defects in the bulk and grain boundary, whereas reductive phenol groups effectively constrain the Sn2+ oxidation. Moreover, the undissociated DACl decreases the supersaturated concentration of tin perovskite solution and creates a pre-nucleation site for rapid nucleation to further regulate crystallization. Consequently, the DACl-derived TPSCs achieve a high power-conversion efficiency (PCE) that reaches up to 11%. More impressively, the device remains at 84% of the initial PCE after full-sun illumination in N2 over 600 h without being encapsulated. This DACl-based synergistic modulation of a lead-free perovskite demonstrates a feasible approach using one molecule with different functional groups to manipulate crystallization, Sn2+ oxidation, and defect reparation of tin perovskite films, providing a critical guideline for constructing high-quality perovskites by multifunctional additives with high photovoltaic performance

Ionic Liquid-Mediated Intermediate Phase Adduct Constructing for Highly Stable Lead-Free Perovskite Solar Cells

The intermediate phase adduct plays a crucial role in constructing uniform and compact tin perovskite films, thus providing an important approach for developing high-performance lead-free perovskite solar cells. However, the common intermediate phase adduct of SnI2·3DMSO in tin perovskite leads to phase separation and may lack compatibility with mixed cation tin perovskites composed of formamidinium (FA) and methylamine (MA), impeding the further device stability. Here, a facile and reproducible method is developed to fabricate high-quality FA0.75MA0.25SnI3 films by introducing a new stable intermediate phase adduct (SnI2·DMSO·MAFa) by using ionic liquid methylamine formate (MAFa). The resulting stable adduct suppresses the reaction rate between ammonium salts and SnI2, thereby modulating the tin perovskite crystallization and precluding SnI2 clusters formation, and the presence of the SnI2·DMSO·MAFa adduct in perovskite precursor serves as a protective barrier for Sn2+ ions, guarding them against oxidation caused by the presence of DMSO. Moreover, the amino and carbonyl groups in residual MAFa could repair the iodine vacancy and uncoordinated Sn2+ ion defects. These features result in the formation of highly uniform and pinhole-free FA0.75MA0.25SnI3 films. The optimized devices achieve a power conversion efficiency (PCE) of over 10%, a value of 53% higher than that of the control device (6.6%). Besides, the obtained MAFa-derived devices illustrate significantly enhanced stability in a microaerobic atmosphere, with 78% maintained initial efficiency over 2800 h of storage under N2 containing 50–100 ppm of O2

Enhancing Photovoltaic Performance by Cathode Interfacial Modification with Inorganic/Organic Gradient Diffusion Structures

The modification of the interfacial contacts between the active layer and the electrode is of great importance in achieving high-performance organic solar cells (OSCs). Herein, a composite film with gradient diffusion structure based on zinc oxide (ZnO) and nonfullerene organic semiconductor of ITIC (G-ZnO/ITIC) is constructed by a convenient one-step solution-processing method for the interfacial modification of OSCs. The facilely constructed G-ZnO/ITIC composite films show enhanced surface hydrophobicity and comparatively smooth morphology, contributing to the improved interfacial contact between the inorganic interfacial layer and organic photoactive layer. Meanwhile, the cascade energy level established inside the bulk G-ZnO/ITIC cathode interfacial layer (CIL) would further assist in the electron-transporting process for efficient charge extraction. Therefore, G-ZnO/ITIC-based PTB7-Th:PC71BM OSCs exhibit power conversion efficiency (PCE) up to 8.73%, which is remarkably larger than these of conventional ZnO-based devices (7.88% for pure ZnO CIL device, 7.27% for ZnO/ITIC bilayer CIL device, and 6.93% for ZnO/ITIC blends CIL device). This gradient diffusion structure is also effective in the PTB7-Th:ITIC-based nonfullerene OSCs, showing improved PCE values from 6.63% to 7.29%. The facilely prepared ZnO/organic semiconductor composite films with gradient diffusion structures and improved device performance would significantly broaden the types of interfacial layers with minimized boundaries among various functional layers, representing an important concept advance in constructing high-performance CILs for OSCs

Regulating Hybrid Anodes for Efficient Li⁺/Na⁺ Storage

Hybrid architectures can effectively integrate the merits of individual components to promote the storage properties of lithium and sodium ions. Herein, a delicate design of Fe7S8@NC@MoS2 with three-dimensional heterostructure is produced via a precise template-engaged strategy by the aid of a metal organic framework and followed by covering in situ formed MoS2 nanosheets. The well-designed anode material shows adjustable voids between the core Fe7S8 and the carbon shell to buffer the volume change upon intercalation and deintercalation of metal ions. Additionally, the outer MoS2 layer enhances both electronic conductivity and metal ion transfer, which further results in fast rate performance for both lithium- and sodium-ion batteries