Improved device efficiency and lifetime of perovskite light-emitting diodes by size-controlled polyvinylpyrrolidone-capped gold nanoparticles with dipole formation.

Herein, an unprecedented report is presented on the incorporation of size-dependent gold nanoparticles (AuNPs) with polyvinylpyrrolidone (PVP) capping into a conventional hole transport layer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The hole transport layer blocks ion-diffusion/migration in methylammonium-lead-bromide (MAPbBr)-based perovskite light-emitting diodes (PeLEDs) as a modified interlayer. The PVP-capped 90 nm AuNP device exhibited a seven-fold increase in efficiency (1.

Molecular Ordering Behavior of Lyotropic Chromonic Liquid Crystals on a Polyimide Alignment Layer.

Coating-type polarizing films with a high dichroic ratio (DR) and polarization efficiency in the visible region were fabricated using a solution of ternary lyotropic chromonic liquid crystals (LCLCs). Optical characteristics of these anisotropic LCLC polarizing films were then determined. DR increased with increasing LCLC concentrations.

Formation of Polymer Walls through the Phase Separation of a Liquid Crystal Mixture Induced by a Spatial Elastic Energy Difference.

We propose a method to form polymer walls without the use of a photomask in a liquid crystal (LC) cell by phase separation of an LC mixture induced by a spatial elastic energy difference. When an in-plane electric field is applied to a vertically aligned cell filled with a mixture of LC and a reactive monomer (RM), a high spatial elastic energy is induced along the direction perpendicular to the interdigitated electrodes. RMs move to the boundaries where the elastic energy is very high and an in-plane component of the applied electric field exists, which results in the phase separation of the LC/RM mixture.

Domain walls and anchoring transitions mimicking nematic biaxiality in the oxadiazole bent-core liquid crystal C7.

We investigate the origin of "secondary disclinations" that were recently described as new evidence of a biaxial nematic phase in an oxadiazole bent-core thermotropic liquid crystal C7. Using an assortment of optical techniques such as polarizing optical microscopy, LC PolScope, and fluorescence confocal polarizing microscopy, we demonstrate that the secondary disclinations represent non-singular domain walls formed in a uniaxial nematic phase during the surface anchoring transition, in which surface orientation of the director changes from tangential (parallel to the bounding plates) to tilted. Each domain wall separates two regions with the director tilted in opposite azimuthal directions.

Surface alignment, anchoring transitions, optical properties, and topological defects in the thermotropic nematic phase of organo-siloxane tetrapodes.

We perform optical, surface anchoring, and textural studies of an organo-siloxane "tetrapode" material in the broad temperature range of the nematic phase. The optical, structural, and topological features are compatible with the uniaxial nematic order rather than with the biaxial nematic order, in the entire nematic temperature range -25 °C < T < 46 °C studied. For homeotropic alignment, the material experiences surface anchoring transition, but the director can be realigned into an optically uniaxial texture by applying a sufficiently strong electric field.

In-plane switching of vertically aligned negative liquid crystals for high transmittance and wide viewing angle.

We propose a method for in-plane switching of vertically aligned negative liquid crystals (LCs) for high transmittance and wide viewing angle. By applying an in-plane electric field using a double-layered electrode structure, LC molecules can be rotated by the vertical as well as the in-plane components of the applied field over the entire region so that high transmittance can be achieved. The threshold voltage difference can be obtained simply by varying the electrode structure, which can reduce the off-axis gamma shift in a multidomain vertical alignment LC cell.

Switching of liquid-crystal devices between reflective and transmissive modes using long-pitch cholesteric liquid crystals.

We propose liquid-crystal (LC) devices capable of switching between reflective and transmissive modes using the scattering and transparent states of long-pitch cholesteric LCs (CLCs). Two different device configurations can be realized by changing the location of a CLC layer. Low-power operation without the parallax problem can be achieved using the bistable switching of CLCs.

Optical configurations for nematic liquid crystal device switchable between reflective and transmissive modes.

We propose an optical configuration for a nematic liquid crystal (LC) device that is switchable between the reflective and the transmissive modes. By placing a reflective polarizer between the two LC layers, we obtain higher reflectance and reduce the parallax effect in the reflective mode. We can eliminate the parallax effect by using a wire-grid polarizer or other in-cell reflective polarizers.

Coexistence of polar and nonpolar domains and their photocontrol in the B7 phase of a bent-core liquid crystal containing azo dyes.

Coexisting polar and nonpolar domains have been studied by means of texture observation, x-ray analysis, optical second-harmonic generation (SHG), and SHG microscopy in the B7 phase of a bent-core mesogen doped with azo dyes. The bent-core molecules take a planar orientation and show high birefringence in the polar domain, while they take a homeotropic orientation and show low birefringence in the nonpolar domain. Good correspondence between real and SHG images was observed under a SHG microscope; the bright (high-birefringent) domain is SHG active and the dark (low-birefringent) domain is not SHG active.