Amplifying Photochromic Response in Tungsten Oxide Films with Titanium Oxide and Polyvinylpyrrolidone.

Tungsten oxide (WO) is known for its photochromic properties, making it useful for smart windows, displays, and sensors. However, its small bandgap leads to rapid recombination of electron-hole pairs, resulting in poor photochromic performance. This study aims to enhance the photochromic properties of WO by synthesizing hexagonal tungsten oxide via hydrothermal synthesis, which increases surface area and internal hydrates.

Large-scale transfer of Ag nanowires from PET to PC film using a roll-to-roll UV lamination process for a capacitive touch sensor.

Demand for flexible transparent sensors for futuristic cars is increasing since such sensors can enhance the freedom of design and aesthetic value in the interior of cars. Herein, we propose a unique roll-to-roll UV lamination process that can expedite large-scale Ag nanowire (AgNW) transfer for a flexible capacitive sensor, using a photocurable resin composed of an epoxy acrylate oligomer, a reactive monomer (1,6-hexanediol diacrylate), and a photoinitiator (1-hydroxycyclohexyl phenyl ketone). The acryl groups in the resin were rapidly crosslinked by UV irradiation, which facilitated the AgNWs transfer from a PET to a PC substrate with the speed of 1050 cm min and enhanced the adhesion between the AgNWs and the PC substrate.

Electron transport and photosynthetic performance in Fragaria × ananassa Duch. acclimated to the solar spectrum modified by a spectrum conversion film.

Functional films have been used in greenhouses to improve the light environment for plant growth. Among them, a spectrum conversion film converting the green light of incident sunlight into red light has been reported to increase the crop productivity. However, the results are not always consistent, and the reasons for the improvement are not fully understood.

Enhancement of Luminescence Efficiency of YO Nanophosphor via Core/Shell Structure.

We successfully fabricated YO:RE (RE = Eu, Tb, and Dy) core and core-shell nanophosphors by the molten salt method and sol-gel processes with YO core size of the order of 100~150 nm. The structural and morphological studies of the RE-doped YO nanophosphors are analyzed by using XRD, SEM and TEM techniques, respectively. The concentration and annealing temperature dependent structural and luminescence characteristics were studied for YO:RE core and core-shell nanophosphors.

Multi-bandgap Solar Energy Conversion via Combination of Microalgal Photosynthesis and Spectrally Selective Photovoltaic Cell.

Microalgal photosynthesis is a promising solar energy conversion process to produce high concentration biomass, which can be utilized in the various fields including bioenergy, food resources, and medicine. In this research, we study the optical design rule for microalgal cultivation systems, to efficiently utilize the solar energy and improve the photosynthesis efficiency. First, an organic luminescent dye of 3,6-Bis(4'-(diphenylamino)-1,1'-biphenyl-4-yl)-2,5-dihexyl-2,5-dihydropyrrolo3,4-c pyrrole -1,4-dione (D1) was coated on a photobioreactor (PBR) for microalgal cultivation.

Luminescent down-shifting CsPbBr perovskite nanocrystals for flexible Cu(In,Ga)Se solar cells.

To overcome the parasitic absorption of ultraviolet (UV) light in the transparent conductive oxide (TCO) layer of flexible Cu(In,Ga)Se2 (CIGS) thin film solar cells, a CsPbBr3 perovskite nanocrystal based luminescent down-shifting (LDS) layer was integrated on CIGS solar cells fabricated on a stainless steel foil. The CsPbBr3 perovskite nanocrystal absorbs solar irradiation at wavelengths shorter than 520 nm and emits photons at a wavelength of 532 nm. These down-shifted photons pass the TCO layer without parasitic absorption and are absorbed in the CIGS absorber layer where they generate photocurrent.

Aggregation induced emission of diketopyrrolopyrrole (DPP) derivatives for highly fluorescent red films.

A large number of diketopyrrolopyrrole (DPP) compounds showing aggregation induced emission (AIE) have been reported in the past few years. However, although DPP compounds exhibited AIE and excellent luminescence properties, their luminescence properties in solid or film states were not much focused on. Here we synthesized and characterized a series of DPP compounds with triphenylamine (TPA) moieties to investigate the AIE properties in the solid film state depending on the functional groups (TPA, BTPA, and MTPA) attached to the TPA moieties.

Optical design of dental light using a remote phosphor light-emitting diode package for improving illumination uniformity.

The projection-type dental lighting based on the remote phosphor light-emitting diode (LED) package is designed to enhance uniformity of illuminance and correlated color temperature (CCT) on a target plane and to remove glare in the eyes of the patient. This dental lighting enables dentists to illuminate effectively the patient's mouth by increasing the inner area (50  mm×25  mm) described in ISO 9680. The optical module comprised of the LED package and optical lens is modeled to satisfy the inner area wider than 100  mm×50  mm and illuminance over 5,000 lx per the designed optical module.

Simple modification of basic dyes with bulky &symmetric WCAs for improving their solubilities in organic solvents without color change.

A simple and easy solubility enhancement of basic dyes was performed with bulky and symmetric weakly coordinating anions (WCAs). The WCAs decreased the ionic character of the dyes by broadening the partial charge distribution and causing a screening effect on the ionic bonding. This new modification with WCAs has advantages in that it has no influence on the optical properties of the dyes.

Analysis and Characterization of Dye-Based Black Matrix Film of Low Dielectric Constant Containing Phthalocyanine and Perylene Dyes.

For liquid crystal display black matrices of low dielectric constant, greenish zinc phthalocyanine dye and reddish perylene dye exhibiting high solubility and thermal stability were employed to fabricate dye-based black matrices. The spectral, optical, thermal and dielectric properties of the dye-based black matrices were tested, and the surfaces of them were investigated using field emission scanning electron microscopy and atomic force microscopy. The dye-based black matrices had sufficiently low dielectric constants and showed satisfactory thermal stability and weaker light absorption property compared with black matrices containing carbon black, due to the low solubility of the dyes and dye aggregations after a post-baking process.

Comparison between organic sensitizers containing stilbene and azo group as bridging unit for dye sensitized solar cells.

While azo dyes have been widely used in dye industry, the azo dyes have been seldom applied as sensitizers to dye sensitized solar cells. In this study, new metal-free organic sensitizers, ST and AZ, which are same structures except bridging units, were synthesized and evaluated. ST containing stilbene as bridging unit gave higher energy conversion efficiency than AZ containing azo group as bridging unit.

Improvement of phosphor modeling based on the absorption of Stokes shifted light by a phosphor.

We have found that the emission spectrum of phosphors measured in the powder state differs from that measured for a single phosphor. When the emission spectrum of the powder state is adopted in an optical simulation, the simulated optical properties e.g.

Electrochemical and optical characterization of cobalt, copper and zinc phthalocyanine complexes.

New phthalocyanine (Pc) derivatives that include the alkyl group in ligand were synthesized based on three core metals such as zinc (Zn), copper (Cu), and cobalt (Co). Electrochemical behaviors and optical properties of the new phthalocyanine derivatives with ligand and different core metal were investigated by using cyclic voltammetry, UV-Visible (UV-Vis) spectroscopy and photoluminescence (PL) spectroscopy. In UV-Vis data, maximum values of 2H, Co, Cu, and Zn complexes were 708 nm and 677 nm, 686 nm, 684 nm, respectively.

Influence of solvent and bridge structure in alkylthio-substituted triphenylamine dyes on the photovoltaic properties of dye-sensitized solar cells.

Three new triphenylamine dyes that contain alkylthio-substituted thiophenes with a low bandgap as a π-conjugated bridge unit were designed and synthesized for organic dye-sensitized solar cells (DSSCs). The effects of the structural differences in terms of the position, number, and shape of the alkylthio substituents in the thiophene bridge on the photophysical properties of the dye and the photovoltaic performance of the DSSC were investigated. The introduction of an alkylthio substituent at the 3-position of thiophene led to a decrease in the degree of redshift and the value of the molar extinction coefficient of the charge-transfer band, and the substituent with a bridged structure led to a larger redshift than that of the open-chain structure.

Effect of five-membered heteroaromatic linkers to the performance of phenothiazine-based dye-sensitized solar cells.

Phenothiazine derivatives with various conjugated linkers (furan, thiophene, and 3,4-ethylenedioxythiophene) were synthesized and used in dye-sensitized solar cells to study the effect of conjugated linkers on device performance. Among them, one with furan as a conjugated linker showed a solar energy-to-electricity conversion efficiency (η) of 6.58%, an improvement of over 24% compared with the T2-1 reference cells' 5.

Lithium-induced supramolecular hydrogel.

We describe a novel anisotropic supramolecular gel made of cyclodextrin-dye, in which physical gelation is completed by lithium salt. Rheological experiment reveals the elastic behaviors of the hydrogel, and high ionic conductivity represents a good mobility of ions inside the gel matrix.

Wood-polyethylene composites using ethylene-vinyl alcohol copolymer as adhesion promoter.

Saw dust-reinforced linear low density polyethylene (LLDPE) (1:1) composites were prepared by using ethylene-vinyl alcohol copolymer (EVAL) as adhesion promoter to improve mechanical strength. To evaluate the optimum vinylalcohol (VA) content in EVAL, various EVAL samples containing different contents of VA were used. The tensile properties of saw dust-LLDPE composites were improved by using EVAL as adhesion promoter in place of ethylene-vinyl acetate copolymer (EVAc).