Ahmet Gun Erlat

Transparent hybrid inorganic/organic barrier coatings for plastic organic light-emitting diode substrates

We have developed a coating technology to reduce the moisture permeation rate through a polycarbonate plastic film substrate to below 1×10−5g∕m2∕day using plasma-enhanced chemical vapor deposition. Unlike other ultrahigh barrier (UHB) coatings comprised of inorganic and organic multilayers, our UHB coating comprises a graded single hybrid layer of inorganic and organic materials. Hardness and modulus of the inorganic and the organic materials are tailored such that they are similar to those of typical glass-like materials and thermoplastics, respectively. In this barrier structure, the composition is periodically modulated between the inorganic and the organic materials, but instead of having distinctive interfaces between two materials, there are “transitional” zones where the coating composition changes continuously from one material to another. Our UHB coating also has superior visible light transmittance and color neutrality suitable for the use of display and lighting device substrates.

Ultrahigh barrier coating deposition on polycarbonate substrates

The use of polycarbonate film substrates enables fabrication of applications, such as flexible display devices, lighting devices, and other flexible electro-optical devices, using low cost, roll-to-roll fabrication technologies. One of the limitations of bare polycarbonate material in these applications is that oxygen and moisture rapidly diffuse through the material and subsequently degrade the electro-optical devices. This article summarizes recent results obtained at GE Global Research to solve the oxygen and moisture diffusion issue. It will be shown that through the application of thin, dense, plasma-based inorganic coatings one can significantly reduce the oxygen and moisture permeation rate through polycarbonate films. However, as a result of defects that are commonly present in these inorganic coatings there is a limit to the performance of such barrier coatings. To further improve the barrier performance, advanced barrier coatings comprising both inorganic and organic materials have been developed. Both modeling and experimental results will be presented that explain why these hybrid material barrier coatings are capable of reaching ultrahigh barrier performance.

A Transparent, High Barrier, and High Heat Substrate for Organic Electronics

The use of plastic film substrates for organic electronic devices promises to enable new applications, such as flexible displays and conformal lighting, and a new low-cost paradigm through high-volume roll-to-roll fabrication. Unfortunately, presently available substrates cannot yet deliver this promise because of the challenge in achieving the required combination of optical transparency, impermeability to water and oxygen, mechanical flexibility, high-temperature capability, and chemical resistance. Here, we describe the development and performance of a plastic substrate comprising a high heat polycarbonate film combined with a unique transparent coating package that is aimed at meeting this challenge.

Substrates and Thin-Film Barrier Technology for Flexible Electronics

The term “flexible electronics” encompasses a wide array of applications such as flexible displays, low-cost and/or large-area sensors, conformal lighting, and solar cells to name a few, with one common ingredient: the ability to fabricate electronic and optoelectronic devices on nonrigid substrates such as plastic films, metal foil, or thin glass, without losing the functionality of the devices during operation. Other terms often used to convey this concept include “printable electronics”, “macroelectronics,” and “organic electronics.” The promise of flexible electronics lies in the potential for building large-area electronic devices with much lower cost than possible with conventional silicon-based technology [1]. The technologies being developed to enable this all revolve around building devices using low-cost printing techniques that are compatible with high-volume “roll-to-roll” manufacturing. Example technologies that are potentially compatible with low-cost printing techniques include organic light-emitting devices (OLEDs) [2–3], organic photovoltaic devices [4–6], thin-film transistors (TFTs) and TFT arrays using both organic [7–9] and solution-processible inorganic materials [10, 11], electronic paper [12], wearable electronics [13], flexible batteries [14], RFID tags [15], sensors [16], and more complicated circuitry [17–19]. Fabricating these devices on flexible substrates, particularly on plastic, brings with it new challenges in order to make them commercially viable. One critical challenge is to design a means of hermetic packaging of the organic electronic device because many such devices exhibit a very short shelf lifetime if not protected from the ingress of environmental permeants such as oxygen and water vapor [20]. Such a packaging scheme can be viewed to have two components. First, the substrate on