Brilliant colors, excellent image quality, high efficiency: OLED displays offer captivating advantages, whether for smartphones or large televisions. So far, producing OLED displays has been complex and costly. However, innovative printing processes, which Merck has been intensively developing for several years, are set to open up a ‟shining new era” soon.

Printing OLEDS: The OLED substances (polymers, small molecules) are dissolved and the resulting inks are applied to a glass substrate by a printer head. Embedded between anode and cathode, the organic molecules are electrically excited, thus producing light.

What was still the future yesterday is now history today in the fast-paced and highly innovative electronics industry. But now comes the next ‟big thing″ in display technology, which experts predict will have enormous potential. Organic light-emitting diodes, or OLEDs for short, are likely to capture the markets in a wide variety of applications soon. They are already lighting up the displays of many mobile phones. And they are also starting to be used in televisions to provide a colorful and contrast-rich viewing experience. There are hardly any limits to the imagination as far as the future use of OLED displays in multimedia is concerned. Transparent screens as well as houses, façades and windows with an enchanting shine, huge display panels and traffic control systems, as well as flexible displays that can be bent, folded and rolled up. Designers are already enthusiastic about the diverse possibilities of filigree illuminated tiles. And the automotive industry is also showing a keen interest in using OLEDs, for example as rear lights.

A shining example

But what makes OLEDs so promising for the future? ‟A major advantage is the fact that semiconducting organic materials light up on their own when an electric voltage is applied,″ explains Herwig Buchholz, Global Head of R&D OLED Chemistry & Strategic Developments at Merck. ‟In contrast to liquid crystal displays, OLEDs do not need any backlighting, so the displays can be extremely thin.″ Every single one of the millions of pixels in a high-resolution TV screen consists of one light-emitting diode each in red, green and blue. Whereas liquid crystals (LCs) act as a switchable filter and still transmit some light even if they are switched to dark, OLEDs only emit colored light when activated. From every viewing angle, this produces extremely high-contrast, sharp, colorful images with very fast response times. Other advantages of organic light-emitting diodes are their long lifetime and high energy efficiency.

Costly vapor

So why haven't OLEDs become the global standard yet? On the one hand, liquid crystals, a well-established field in which Merck is the market and technology leader, continue to meet increasing quality requirements. On the other hand, OLED production poses a challenge as it is still very complex and costly. For each diode, several ultrathin layers of material must be deposited with pinpoint precision in very small portions onto a glass plate. The closer the diodes are to one another, the higher the resolution of the display. In the currently prevailing coating process, a metal mask is used to evaporate and deposit the OLED materials. This process is repeated several times with different materials and masks. High costs and low material utilization are major disadvantages of this process. More than half of the OLED materials are lost during deposition. And last but not least, the energy and environmental footprint of this method is rather modest. ‟For technical and financial reasons, the evaporation method has limitations in the mass production of large-area OLED displays,″ says Anja Jatsch, Project Manager OLED Formulation. ‟For television screens, our customers are currently using a process that combines white OLEDs with color filters. This is yielding very good results for televisions with very large screens.”

Both mass and class

The key to future success is an innovative printing technology that Merck has been developing intensively for several years. The pioneering achievement combines the advantages of two different classes of materials – printing solutions of small molecules and semiconducting polymers. Small soluble molecules significantly increase the coating efficiency, while the printing process makes it possible to coat large surfaces with high homogeneity and low material consumption. ‟The use of inkjet technology brings the mass production of large OLED television screens within reach,” says Jatsch.

Merck OLED researchers (from left) Herwig Buchholz, Leticia Garcia Diez, Remi Anemian and Anja Jatsch during a project meeting.

“Different cultures and working methods come together in our international and interdisciplinary teams. This creates a highly innovative and stimulating environment. Coupled with our enthusiasm for developing new technologies, this contributes significantly to the success of our products.”

Herwig Buchholz, Global Head of R&D OLED Chemistry and Strategic Developments

Anja Jatsch, Head of the formulation laboratory, preparing an OLED printing ink.

“The use of inkjet technology brings the mass production of large OLED televisions within reach.”

Anja Jatsch, Project Manager OLED Formulation

In order to advance the innovation process using inkjet printing inks, Merck has been collaborating closely with Seiko Epson since October 2012. The Japanese company is among the world’s leading printer manufacturers. ‟We are working together on transforming our high-quality OLED materials into printing inks that can be applied by inkjet printing systems,” says Leticia Garcia Diez, Project Manager OLED Ink Technology at Merck. Very high requirements are placed on these inks. After formulating the OLED materials, they must be rapidly printable in error-free superior quality – in huge printers with a large number of print heads.

Remi Anemian in front of an interactive OLED mirror.

Endless team spirit

Step by step, scientists are optimizing OLED inks with regard to their electro-optical properties, drop and film formation, printing of stacks of different layers, and adaptation to the print heads. A global team of chemists, physicists, engineers and materials scientists are mastering these challenges. Last but not least, marketing experts at Merck are also using the close contacts they have to their customers, namely display manufacturers from the liquid crystals business. After all, the OLED inks, delivered in special cartridges, are soon to be marketed worldwide. ‟Different cultures and working methods come together in our international and interdisciplinary teams,” says Herwig Buchholz. ‟This creates a highly innovative and stimulating environment. Coupled with our enthusiasm for developing new technologies, this contributes significantly to the success of our products.”

Organic growth

Merck is already very well-positioned in the OLED materials market. The high investments Merck is making at several locations underscore the company’s confidence in the future success of organic light-emitting diodes. ‟In our new R&D and application laboratory in Korea, for example, we are collaborating closely with key customers. In addition to the continuous development of materials for today’s coating processes, we are running exciting pilot projects to test the printing processes in large-scale production. The first market launches of printed OLED displays could be possible in 2017,” says Remi Anemian, Head of Global Technical Marketing OLED. And in Darmstadt, Merck laid the cornerstone for a new production plant in June 2015. Production of high-purity OLED materials for use in displays and lighting systems is scheduled to start in the approximately 2,000 square meter building in summer 2016. By investing around € 30 million, the company is further strengthening its position in this promising business. It’s an ambitious goal: By 2018, Merck also aims to be the world’s leading supplier of printable OLED materials.