White light OLED and OLED manufacturing process

White OLED

1.1 Basic structure of white OLED
White can be obtained by combining the three primary colors red, green, and blue, as shown in Figure 1. In OLED lighting, white light can be obtained by mixing the three primary colors (red, green, blue) emitted from different light-emitting layers or by mixing two complementary colors. Figure 2 shows white light formulated using two and three color mixes. For lighting applications, white light OLEDs do not require three-color mixing, only two colors can be used to get white light.

Figure 1 - White is obtained by combining red, green, and blue primary colors — Figure 1 – White is obtained by combining red, green, and blue primary colors

Figure 2 - White light configuration method — Figure 2 – White light configuration method

OLED manufacturing process

The manufacturing process of OLED for lighting includes: ① substrate treatment; ② deposition of organic material layer by vacuum thermal evaporation or dissolution process; ③ deposition of cathode electrode; ④ cathode packaging; ⑤ module assembly process, including driving circuit. FIG. 3 is a block diagram of a traditional OLED manufacturing process. Figures 4 and 5 show, respectively, an anode patterning lithography apparatus and a vacuum thermal evaporation apparatus with a glove box for depositing organic material layers and cathode metals.

Figure 3 - Block diagram of traditional OLED production process — Figure 3 – Block diagram of traditional OLED production process

Figure 4 - Anode Pattern Lithography Equipment — Figure 4 – Anode Pattern Lithography Equipment

OLEDs are sensitive to water vapor and oxygen, so in order for OLEDs to last longer, they must be isolated from water vapor and oxygen. Likewise, thin-film barrier layers have become a prerequisite for OLED fabrication. To determine this, the Fast2Light Consortium (a group of 14 companies, research institutes and academies in Europe) developed a standard for measuring the properties of thin film barriers, the measurement of barrier properties and the selection of barrier materials. Like standardization, is a fundamental and important factor. The Fast2Light Alliance was formed to demonstrate the high quality and low cost of OLED lamps for future lighting and signage applications.

For the fabrication process of a large-area device, the factors that affect the efficiency and cost competitiveness of the fabrication of OLED light sources need to be considered, as shown in Table 1.

Table 1 - Efficiency of OLED Light Source Fabrication Factors Affecting Its Efficiency and Cost Competitiveness — Table 1 – Efficiency of OLED Light Source Fabrication Factors Affecting Its Efficiency and Cost Competitiveness

Implementation method of white light OLED

White OLED lighting has been used in special lighting and high-end lighting. According to the current development, it can be divided into two lighting systems according to the deposition process and the solution process. Most companies are stepping up the development of white light OLEDs using a single deposition process, and the lighting market for OLEDs may also open up from commercial products based on monomer materials. Although OLED lighting has not yet been commercialized, many developers have made a series of announcements about the results of OLED’s superiority, and mass production of OLED lighting has accelerated in recent years.

Since the introduction of white OLED in 1995, due to the development of a series of breakthrough technologies, the application of white OLED lighting has been realized, and some corresponding performance parameters have also been greatly improved. So far, the best announced is 2006 Konica Minolta (Konica Minolta, KM) announced that its efficiency reached 64lm/W, the efficiency of white OLEDs is better than incandescent lamps, but not as good as fluorescent lamps. However, the 10000h lifespan of OLED has been achieved, which is a necessary condition for opening the market. Therefore, at the current development speed, it does not take a long time to realize the commercialization of OLED. Level.

Philips and Nova led have achieved a new record in the luminous efficiency of white OLEDs, achieving a luminous efficiency of 32lm/W. At a brightness of 1000cd/m2, its International Commission on Illumination (CI Ex,y) color coordinate is (0.47 , 0.45), the color rendering index CRI is 88, and the OLED with the same device structure has exceeded the lifetime of 20000h, which is a great achievement for the commercialization of OLED in lighting applications in the future.

Recently, General Electric (GE) and Konica Minolta (KM) announced the use of solution coating technology instead of vacuum coating process to achieve a flexible white OLED lighting device with a luminous efficacy of 56lm/W, and its lifespan has reached commercialization requirements. This can be achieved with high volume roll-to-roll manufacturing techniques that are well established in the printing industry.