Surface Engineering of Titanium Dioxide Nanoparticles for Silicone-Based Transparent Hybrid Films with Ultrahigh Refractive Indexes

Transparent and High-Refractive-Index Titanium Dioxide/Thermoplastic Polyurethane Nanocomposites

Transparent nanocomposite films made of surface-modified titanium dioxide nanoparticles and thermoplastic polyurethane are prepared via film casting approach showing enhanced refractive indexes and mechanical properties. Two different sets of composites were prepared up to 37.5 wt % of inorganic nanoparticles with a diameter <15 nm, one set using particles capped only with oleic acid and a second one with a bimodal system layer made of oleic acid and mPEO-5000 as coating agents. All of the composites show significantly enhanced refractive index and mechanical properties than the neat polymeric matrix. The transparency of nanocomposite films shows the excellent dispersion of the inorganic nanoparticles in the polymeric matrix avoiding aggregation and precipitation phenomena. Our study provides a facile and feasible route to produce transparent nanocomposite films with tunable mechanical properties and high refractive indices for various applications.

Dopamine Sulfonate Ligand-Assisted TiO2 Deposition Enabling Highly Efficient and Stable Perovskite Solar Cells

The metal oxide electron transport layers (ETLs) with flat morphology and high electrical quality are essential to manufacture highly efficient perovskite solar cells (PSCs), in which the regulation of the metal oxide deposition process plays a crucial role. Herein, a judiciously designed dopamine sulfonate (DS) ligand-assisted deposition of titanium dioxide (TiO2) films approach is implemented based on electrostatic repulsion and steric hindrance of assembled ligands to improve colloidal nanoparticles dispersity in precursor and effectively inhibit their aggregation, which could enable obtaining smooth topography of TiO2 films and initiating growth of top high-quality perovskite films. Furthermore, sulfonate bridges bonded on the perovskite buried layer that is beneficial to form better buried interface contact and accelerate electron extraction. As a result, the PSCs employing DS/TiO2 ETLs exhibit the best power conversion efficiency of 24.53% with impressive storage stability and operation stability, i.e., remaining more than 88% of their initial efficiency upon storage N2 glovebox without encapsulation over 4000 h, and the efficiency does not attenuate significantly under maximum power point for 60 h.

Influence of an External Electric Field on Electronic and Optical Properties of a g-C3N4/TiO2 Heterostructure: A First-Principles Perspective

In this study, calculations based on density functional theory (DFT) were utilized to examine how electrostatic fields affect the electrical and optical characteristics of g-C3N4/TiO2 heterostructures. The binding energy, density of states, difference in charge density, and optical absorption spectra of the heterostructure were calculated and analyzed to reveal the mechanism of the influence of the external electric field (EF) on the properties of the heterostructure. The results show that the binding energy of the heterogeneous structure is reduced due to the imposed electric field in X- and Y-directions, and the optical absorption spectrum is slightly enhanced, but the BG and charge transfer number are basically unchanged. On the contrary, applying the electric field in the Z-direction increases the binding energy of the heterogeneous structure, decreases the BG, increases the number of charge transfers, and red shifts the optical absorption spectrum, which improves the photocatalytic ability of the g-C3N4/TiO2 heterostructure.

Unraveling Optical and Electrical Gains of Perovskite Solar Cells with an Antireflective and Energetic Cascade Electron Transport Layer

Electron transport layers (ETLs) are imperative in n-i-p structured perovskite solar cells (PSCs) because of their capability to affect light propagation, electron extraction, and perovskite crystallization, and any mismatch of optical constants, band position, and surface potential between the ETLs and the perovskites can cause unintentional optical and electrical losses. Herein, an antireflective and energetic cascade bilayer ETL with ubiquitously used SnO₂ and TiO₂ was constructed at 150 °C for PSCs, and the in-depth mechanism for performance improvement was systematically unraveled. It was revealed that the construction of an ETL with gradually increasing refractive indices can circumvent light reflection loss, resulting in enhanced photocurrent. The combined ETL forms an energetic cascade to promote electronic conductivity and facilitate electron extraction with reduced energy loss. Moreover, topologic perovskite growth with improved crystallinity and vertical orientation was preferred owing to the relative dewetting behavior, leading to reduced defect states and enhanced carrier mobility in the perovskite layer.

Zirconia/phenylsiloxane nano-composite for LED encapsulation with high and stable light extraction efficiency

To obtain a rapid processible LED encapsulant that leads to high and stable light extraction efficiency (LEE), UV curable ZrO₂/phenyl-siloxane nano-composite (ZSC) double-layer encapsulants were prepared and optimized. The highly crystalline ZrO₂ nanoparticles with a diameter of ∼14 nm were synthesized through a modified hydrothermal method at mild conditions, and a UV curable methacryl-diphenyl-polysiloxane (MDPS) with a refractive index (RI) of 1.54 (at 633 nm) was synthesized from self-condensation of diphenylsilanediol and an end-capping reaction. High refractive indexes (RIs) from 1.54–1.61 have been obtained for ZSC composites by adding 0–20 wt% ZrO₂. Before and after sulfur vapor erosion, the double-layer encapsulated sample (M-10/M) showed 11.2% and 64.8% higher LEE respectively than that of Dow Corning OE-7662. Meanwhile, the variation of LED light color temperature (T_c) was less than 1%. The effect of the ZrO₂ nanoparticle content on LEE of double-layer and single-layer encapsulation were compared and discussed based on Fresnel loss and Rayleigh scattering theories. The double-layered UV curing processing took only 1/6 of the time needed for common thermal curing.

The double-layer encapsulation by a highly crystalline ZrO₂/polydiphenylsiloxane composite affords 11.2% and 64.8% higher LEE respectively than that of OE-7662 before and after sulfur vapor erosion.