Organic electronics, from OLED displays and lighting to third generation photovoltaic modules, is an enabling technology platform promising lighter, cheaper, and more flexible devices for a wide variety of industries and applications. The recent proliferation of organic-empowered devices like Samsung’s AMOLED displays in their Galaxy line of smartphones and tablets shows just how far we’ve come over the last few years. However, we still have yet to see the truly transformational devices on a large-scale inconceivable with their non-organic analogs (e.g. fully printed, flexible HDTVs).
One major impediment to the mass production of transformational OLED devices is insufficient product lifetimes caused by OLEDs’ propensity to stop functioning when exposed to water vapor, oxygen, and other detrimental compounds present in the air. These contaminants can cause serious performance issues if they come in contact with the active polymer or small molecule layers of an organic-enabled device. Encapsulation materials, also known as barrier films, are a necessary and often overlooked part of the OLED/OPV device architecture. High performing and inexpensive encapsulation material technology is paramount to the realization of novel and exciting organic electronics devices in the near future.
Many different technological approaches have been proposed and prototyped to address this market need. Encapsulation technology is an active area of deal flow here at Pangaea Ventures and a space we continue to monitor with interest. There probably will not be one clear winner in this technology race as the wide array of organic electronics products and applications carry different requirements including but not limited to cost, barrier performance, flexibility, transparency, and processing methods. The following is a brief run-through of the various technological offerings available to address organic electronics’ current lifetime deficiencies.
Glass: Glass is the dominant encapsulation technology today and is well suited for rigid devices like smartphones. With good barrier and optical properties as well as established manufacturing and integration processes, glass will continue to provide a viable solution for most of the organic electronics market in the short term. Continued developments in flexible glass compatible with some level of roll-to-roll (R2R) processing continue to push the glass envelope for the encapsulation of conformable and/or flexible electronics. Both Asahi Glass Co. and Corning Inc. have released ultrathin 0.1 mm thick flexible glass sheets and rolls amenable to R2R manufacturing.
Multilayer Films: Multilayer films are an encapsulation alternative to glass. Currently, the leading multilayer film architectures consist of alternating layers of organic (polymer) and inorganic (oxide) materials either deposited directly atop (monolithic) or laminated onto the device stack. Compared to glass, multilayer films can be made thinner significantly with relatively low cost materials. Unfortunately, these material cost advantages rarely translate to money-saving on the whole: many of these systems require so many different layers and compositions to be effective that increased processing cost and complexity far outweigh any material cost savings. More layers usually means less flexibility as well. It is worth noting here that some promising work is being done on improved architectures like an inorganic-only trilayer approach that could cut costs significantly for OPV modules now and OLEDs in the near future.
Single Layer Barrier Films: A single-layer monolithic barrier film meeting or exceeding the metrics for water transmission rates, flexibility, visual light transmission, throughput, and perhaps most importantly, cost, is the ideal encapsulation technology. While big and small companies alike are making progress using a variety of approaches and materials, a cost effective, high performance single layer barrier film has not yet been achieved on the scale necessary for mass production to my knowledge. If you think you have one, do tell one of us here at Pangaea Ventures!
Because oxide films have to be of high quality to provide superior barrier performance, atomic layer deposition and sputtering are being pursued as alternatives to traditional chemical and physical vapor deposition methods. Reducing the number of defects (pinholes, grain boundaries, etc.) can reduce the layer thickness and/or number of layers required to achieve the needed water vapor transmission rates (g/m2/day). However, these high-quality deposition methods usually come with increased costs and lower throughputs, relegating some encapsulation techniques to high-value, niche applications only.
As water is one of the key enablers of life on this planet, perhaps improved encapsulation technology will prove to be one of the key enablers of organic electronics in novel addressable markets like OLED lighting.
Water may be the cleaning agent of choice for a great number of life’s situations, but it is about the worst solution for cleaning up organic electronics’ dirty little lifetime secret.