Performance enhancement using a stable low-pretilt molecular configuration and a novel driving method for optically compensated bend liquid crystal devices.

A stable low-pretilt molecular configuration (SLPMC) is successfully developed in optically compensated bend (OCB) liquid crystal (LC) devices by simultaneously employing the curing voltage and surface-anchored crosslinking monomer during the polymerization process. For the SLPMC OCB cell with the low-bend state, the warm-up voltage making the LC molecules reorient from the splay to the bend state is annihilated, and the transient twist state occurring as the driven LC molecules recover from the bend to the splay state is also eliminated. In addition, with the novel driving method selecting the specific driving point, the proposed SLPMC OCB cell not only exhibits a good response performance, but also outputs a higher light transmittance, which is superior to the conventional OCB and no-bias-bend cells. This Letter demonstrates an effective SLPMC fabrication method, and points out the significant contributions of SLPMC on the electro-optical properties, which will benefit and enhance the performance design in OCB-based applications.

Effects of the vertically switching electric field on the photoelectric properties of polymer-stabilized blue-phase liquid crystal cells using the director model.

This study uses the director model to analyze the optoelectronic properties of polymer-stabilized blue-phase liquid crystal (PS-BPLC). The director model revealed a linear relationship of refractive index change and the cosine squared of the angle between the LCs and the direction of the electric field. Moreover, we employed simulations based on the Kerr effect and compared the results with those of the director model. The simulation results also show high consistency with real circumstances. Consequently, it can be of great help to design BPLC displays that can be applied to adopting better strategies for developing next-generation LCD devices.

Effects of cell gap on the optoelectronic properties of pure blue-phase liquid crystal devices: estimating the Kerr constant.

In this study, the Kerr constant of pure blue-phase liquid crystal (BPLC) without polymer doping at room temperature and the optoelectronic properties dependent on the cell thickness are explored. The relation between the phase and the voltage in oblique incident light was measured via a reasonable vertical electric field for different thicknesses of BPLC cells. It was found that the Kerr constant formula can be amended with the functions related to the cell gap. This study demonstrates a method to estimate the Kerr constant, especially for cells within a small electrical field, which will benefit optoelectronic applications.

Light extraction enhancement with radiation pattern shaping of LEDs by waveguiding nanorods with impedance-matching tips.

Syringe-like ZnO nanorods (NRs) were fabricated on InGaN/GaN light emitting diodes (LEDs) by a hydrothermal method. Without sacrificing the electrical performances of LEDs, syringe-like NRs can enhance light extraction capability by 10.5% at 20 mA and shape the radiation profile with a view angle collimated from 136° to 121°. By performing optical experiments and simulation, it is found that the superior light extraction efficiency with a more collimated radiation pattern is attributed to the waveguiding effect of NRs and the mitigation of abrupt index change by the tapered ends of syringe-like ZnO NRs. This work demonstrates the importance of the nanostructure morphology in LED performances and provides the architecture design guidelines of nanostructures to a variety of optical devices.

Characterizations of low-temperature electroluminescence from ZnO nanowire light-emitting arrays on the p-GaN layer.

Low-temperature electroluminescence from ZnO nanowire light-emitting arrays is reported. By inserting a thin MgO current blocking layer in between ZnO nanowire and p-GaN, high-purity UV light emission at wavelength 398 nm was obtained. As the temperature is decreased, contrary to the typical GaN-based light emitting diodes, our device shows a decrease of optical output intensity. The results are associated with various carrier tunneling processes and frozen MgO defects.