Chang‐Jae Yu

An extremely high degree of circularly polarized photoluminescence (CPPL) and electroluminescence (CPEL) (dissymmetry factor values: | g PL | = 0.72 and | g EL | = 1.13) are generated from twisted stacking of achiral conjugated polymer induced by nonemitting chiral dopant of high helical twisting power for the first time. Using a theoretical analysis incorporating the Stokes parameter, the twisting angle and birefringence of the aligned conjugated polymer, and the degree of linear polarization i

The direct emission of circularly polarized (CP) light improves the efficiency of an organic light-emitting diode and characterizes the secondary structure of proteins. In most cases, CP light is generated from a luminescent layer containing chiral characteristics, thereby generating only one kind of CP light in an entire device. Here, we propose direct CP light emissions using a twisted achiral conjugate polymer without any chiral dopant as an emitting layer (EML). The twisted structure is indu

We demonstrate a transflective liquid crystal display (LCD), doped with a chiral agent to produce a low helical twisting power, in a multimode configuration consisting of the homogeneous alignment and the hybrid alignment. The multimode transflective LCD was fabricated by a single-step exposure of the UV light through an array of metal reflectors used as an amplitude photomask which gives an alternating homogeneous and homeotropic LC geometry. This single-step UV exposure produces no cell gap va

The measured<italic>g</italic>factor and the corresponding emission zone were evaluated by theoretical analysis based on the Müller matrix method by increasing the thickness of the hole transport layer (TPBi) in the twisted configuration of conjugate polymer (F8BT).

We demonstrate a polarization-invariant liquid-crystal (LC) grating in an oppositely twisted and mutually orthogonal configuration. The polarization-invariant LC grating with high diffraction efficiency is fabricated using a single-masking process with two-step exposure of a linearly polarized ultraviolet light. It is found that the zeroth- and the first-order diffracted beams are linearly polarized and perpendicular to each other irrespective of the incident polarization for the phase retardati

We report on a linearly graded phase model for the design of binary diffraction gratings of liquid crystals (LCs) associated with the periodic interfacial effect. The binary nature of the LC grating is produced by use of periodic striped domains in an alternating homeotropic and hybrid geometry. In our graded phase model the diffraction patterns and the diffracted intensities of the LC binary grating is primarily governed by three length scales: the cell thickness and two distortion parameters s

Abstract We report on a transflective liquid crystal display (LCD) in a multimode configuration consisting of an electrically controllable birefringence mode and a hybrid aligned nematic mode. In this configuration, the multimode transflective LCD was obtained by a single‐step exposure of ultraviolet light, blocked by a metal reflector in the reflective area as an amplitude photomask, producing an alternating homogeneous and homeotropic geometry with no additional fabrication processes and cell

The ferroelectric nematic ordering of finite-length hard spherocylinders with longitudinal dipoles is demonstrated in an extended version of the Onsager formalism. The stability analysis as well as numerical simulations were performed to obtain a complete phase diagram for the ferroelectric nematic order in terms of the dipolar strength and the packing fraction of the system. The phase diagram exhibits a usual isotropic-nematic, a nematic-ferroelectric nematic, and a direct isotropic-ferroelectr

Abstract Direct circular polarized (CP) emission from a twisted mesogenic luminophore is one of the promising approaches for generating high degree of CP light since device parameters governing the degree of CP emission are easily controlled. Most high CP emissions have been performed by solution process since a twisted structure of mesogenic luminophore is easily achieved. However, since solution process has been impeded by the limitation of low resolution and efficiency, vacuum evaporation has

In the in-plane optical geometry, the achromatic and viewing properties of reflective liquid crystal displays (LCDs) are studied within the framework of the 2 ×2 Jones matrix formalism. For obtaining high brightness, high contrast and good achromaticity, LCD cell parameters such as the molecular rotation angle of LC and the effective phase retardation through the LC layer are optimized in the geometry such that the average optic axis of the LC layer lies on the plane parallel to the substrates.

We present basic principles of designing and fabricating high-performance liquid crystal (LC) gratings with binary alignment structures which produce a variety of the diffraction properties. The periodic binary structure in the LC layer was fabricated through a selective irradiation of the UV light using the single-masking process. An alternating homeotropic and hybrid alignment configuration produces the input polarization-dependent diffraction suitable for the polarization-separating devices w