OLED's barrier films and thin film encapsulation: IDTechEx's review

July 25, 2019 //By Julien Happich
barrier film
Flexible and foldable high-performance barrier or encapsulation technology had long represented a technology challenge. The industry spent a decade and a half optimizing the approaches and the processes to achieve large-area production-grade results.

In this article, market research firm IDTechEx's provides a brief overview of the evolution of the technology to its current status and consider some of the latest technology trends that seek to replace current incumbent techniques. The overview is drawn from the company’s report “Barrier Films and Thin Film Encapsulation for Flexible and/or Organic Electronics 2019-2029”.

 

Roll-to-roll barrier film production

The performance requirements for flexible barrier layers were, and are, difficult to meet. The barrier requirements are often expressed in terms of WVTR (water vapor transition rate) and vary from 1e-3 to 1e-6 g/sqm/day, depending on the application. This is many orders of magnitude beyond the ability of plastic substrates to meet. As such, layered and highly-engineered barriers were required.

Furthermore, the encapsulation layer must (a) exhibit low stress to prevent cracking and delamination during repeated bending, (b) offer high optical transparency, and (c) benefit from high deposition rates over large areas to drive down TACT. Ideally, the overall structure can also be made extremely thin to enable a development roadmap towards and beyond a 1mm bending radius and can be manufactured at high yield with few deposition machines and steps. Clearly, simultaneously satisfying all these requirements has been, and remains, a technological and an engineering challenge.

As such, over the years, numerous technologies have been proposed and developed to meet this WVTR. In general, thus far, a multi-layer structure has mainly been utilized. This structure consists of alternative dyes of organic and inorganic materials. The alternative structure decouples the position of the defects, creating a tortuous path. The generally much thicker organic layer serves to planarize the surface, covering larger particulate and plugging pinholes, whilst also acting as a stress release structure to promote flexibility.


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