Zhang Fanghui

Research of factors for the response of LCDs

Slow response is one of the main restricted factors for the development of LCDs. This paper describes the principle and methods for reducing the response time of LCDs. The total display process is divided into three stages in this paper: the polarization stage, the rotation stage, and the recovery stage. And then the influence factors for each stage are discussed separately from the point of characteristics of LCD molecule, driving characteristics and charge accumulation effect. Results show that response time of LCDs can be improved by using the fast polarized LC materials, reducing the rotation time of LC molecule, and eliminating the charge accumulation effect, with the result of better display quality.

Luminescence mechanism of polymer light-emitting devices with MEH-PPV: PVK emitting layer

Four kinds of single layer PLED devices are prepared by using MEH-PPV, PVK, MEH-PPV:PVK and MEH-PPV:PVK:OXD-7 as material of emitting layer respectively in this paper. And the luminescence spectrums of the four devices are analysised based on the measured spectrograms. It is found that the electroluminescence spectrum ranges of MEH-PPV and PVK are all wide. The spectrum of MEH-PPV is concentrated on the fields of red and yellow; the spectrum range of PVK covers the whole light spectrum range, and the spectrum intensity is higher in the short wavelength region compared with that of the long wavelength region; the spectrum range of MEH-PPV:PVK also covers the whole light spectrum, but the brightness for the range of 500--540nm wavelengths increases as the light wavelength increases and two kinds of models are proposed here, which can explain the unusual zone perfectly; Ray intensity of short wavelength of PLEDs can be increased by adding OXD-7 because of its contribution on the transportation of electron, and by this way the energy of exciton can be improved greatly, and so rays brightness of short wavelength will be increased, with the result of much purer white light emitted by this type of PLED device.