Going beyond the limit of an LCD’s color gamut

Abstract

In this study, we analyze how a backlight’s peak wavelength, full-width at half-maximum (FWHM), and color filters affect the color gamut of a liquid crystal display (LCD) device and establish a theoretical limit, even if the FWHM approaches 1 nm. To overcome this limit, we propose a new backlight system incorporating a functional reflective polarizer and a patterned half-wave plate to decouple the polarization states of the blue light and the green/red lights. As a result, the crosstalk between three primary colors is greatly suppressed, and the color gamut is significantly widened. In the experiment, we prepare a white-light source using a blue light-emitting diode (LED) to pump green perovskite polymer film and red quantum dots and demonstrate an exceedingly large color gamut (95.8% Rec. 2020 in Commission internationale de l'éclairage (CIE) 1931 color space and 97.3% Rec. 2020 in CIE 1976 color space) with commercial high-efficiency color filters. These results are beyond the color gamut limit achievable by a conventional LCD. Our design works equally well for other light sources, such as a 2-phosphor-converted white LED. A liquid-crystal display that produces a wider range of colours than current commercial devices has been created. Shin-Tson Wu from the University of Central Florida and co-workers achieved this by determining the optimal optical characteristics of a liquid-crystal display backlight. Colour liquid-crystal displays work by using a layer of electrically controlled molecules to block emission from a white-light source. The optical properties of this white backlight determine the full range of colours created by the display, referred to as its gamut. Wu and colleagues created a backlight based on a blue light-emitting diode combined with quantum dots and a perovskite polymer film. They then optimized the emission by adding a reflective polarizer and a half-wave plate, and hence increased the gamut of the display.