High Performance Color Conversion Polymer Films and Their Application to OLED Devices

Abstract

When dye molecules absorb light, they emit light at a different, generally red-shifted, wavelength. This is a principal characteristic of dye molecules and is applied in many fields, such as laser systems, lighting, and displays. In this article, we report highly efficient color-conversion polymer films and their application to full-color, active-matrix (AM), organic light emitting diode (OLED) displays. Since they were first reported by Tang and van-Slyke [1], OLEDs have attracted much attention for application to next-generation displays. During the past decade, several commercial products have been developed using small OLEDs fabricated by vacuum evaporation. However, OLED manufacturing is still problematic, especially for full-color displays. Figure 1 outlines three typical methods for fabricating full-color, OLED displays. Side-by-side patterning for red-green-blue (RGB) using shadow masks has been the most commonly used method [2], but using shadow masks is costly. Moreover, the substrate size and display resolution are limited. Using OLEDs with color filters (CFs) eliminates the need for shadow masks and is suitable for large-scale high-resolution displays [3, 4]. The CFs are used with white OLEDs to attain full-color functionality. However, the transparent spectral band of the CFs must be narrowed to expand color gamut, leading to a reduction in the amount of light emitted by the white OLEDs. Therefore, balancing high efficiency with a wide color gamut is difficult. A good way to overcome this trade-off without losing the advantages of the color filter method is to use a color conversion material (CCM) that converts the blue spectrum of the OLED emission into red and green spectra [5-7]. If a polymer is used as the CCM, patterning can be achieved using a low-cost printing technology, such as ink jetting. Use of a CCM is thus a promising alternative for manufacturing large-scale, full-color OLED displays. In this article, we report high-efficiency CCM films made using various polymers and their application to AM-OLED displays.