Application-Driven Organic Electronics Workshop

The IEEE Solid-State Circuit Society’s Long-Range Planning Committee has launched an effort to explore profound changes in circuit and system design in the post-Moore era and their potential implications on applications, interdisciplinary collaboration, and the role of the society as a service organization. As a member of that committee, Professor Hugo DeMan has stated that the biggest challenge to this ambitious goal is “to bring visionary people together who are willing to start a dialogue on what future microsystems will look like and how we will join forces to make progress in this new field of ‘super circuit’ design.” The Solid-State Circuit Society has the right combination of long-term vision coupled with the practical realities of commercial design to play a major role in stimulating creative thinking. A major challenge in this effort is to determine the mechanisms that are best suited to stimulate a dialogue among disciplines that we envision will become well-connected.

To stimulate development of working research relationships we replaced the traditional workshop format of a packed one- or two-day schedule of several talks with a workgroup approach. We assembled a small gathering in a setting conducive to creativity, with ample time to brainstorm and discuss the possibilities among a few visionary individuals from relevant disciplines. The first such workshop, “Application-Driven Organic Electronics,” was held in late June at the MIT Endicott House.

Active organic electronic components such as organic transistors, solar cells, photodetectors, and LEDs likely will be the enabling blocks of future low-cost flexible electronics and integrated large-area optoelectronic circuits. The organic materials break the paradigms of silicon technologies in that their unconventional processing methods enable integration with flexible conformal substrates from centimeters to meters in size. However, this technology is compromised by the lower charge carrier mobility of organic solids and the unproven reliability of devices made with organic materials. Nevertheless, the utility of organic materials in display applications has already been demonstrated. Their use in low-performance integrated electronic circuits, driven by the potential for low-cost organic electronic systems, is being explored.

In the late 1960s, silicon MOS technologies were at a stage similar to organic electronics today. DRAM served as the driver for MOS devices from approximately 1970 to 1985, encompassing DRAM generations from 1 kb to 1 Mb. The DRAM application was not exclusive but helped to focus research in silicon process technology as well as device and circuit design.

Current research in organic electronics is focused primarily on the improvement of discrete devices. This focus is expected, considering that the physical processes within organic devices are still being discovered. In the near future it is expected that the integration of organic light-emitting diodes (OLEDs), organic photodetectors (OPDs), and organic field-effect transistors (OFETs) will be integrated into circuits that control electrical and optical signals. The challenge for the workshop was: What application platform will best drive this integration?

It would be folly for organic electronics to try to replace silicon digital processing and memory applications since its strengths are not suitable for these functions. Instead, workshop participants suggested that successful commercial applications will take advantage of the inherent attributes of organic material: low cost, mechanical flexibility, chemical sensitivity, optical properties, and the potential for integrated large-area optoelectronic circuits. Identifying the commercially viable organic electronics application drivers and outlining the research necessary to demonstrate these practical applications was the challenge posed to the workshop participants.

To start, we asked ourselves what proven organic technologies have reached the marketplace. Applications that take advantage of the optical properties of organic devices already have been extremely successful in optical recording, liquid crystal displays, and photoconductors—generating approximately a $100 billion business. Up to this point we have not seen many commercially viable electronic or optoelectronic systems based on organic technology because moving charges is not an inherent advantage of organic devices. It is clear that the application drivers for organic electronics should leverage the excellent optical properties and require minimum performance from associated electronics.

Although many researchers are publishing results for discrete OLEDs, OFETs, and OPDs, little work has been done on developing a process flow for the integration of these devices. It is clear that one of the major challenges to move organic electronics from the research lab to commercial viability is the convergence on a single process flow. The fact that different active materials and different dielectrics are being employed to fabricate devices has made the convergence on a single process flow extremely difficult. In addition, there are no standard characterization techniques to fairly compare performance metrics between different device structures. So what are the applications that will drive us to develop a standard integrated all-organic process?

Three possible application drivers were discussed during the workshop. The first is a digital X-ray detector using OPDs. This detector could be used in medical applications, diagnostics, failure analysis, security, and a variety of scientific equipment. It was suggested that a large array of applications are possible since the detector may be fabricated on a non-planar substrate. This application is attractive since it takes advantage of several attributes of organic technology. However, it is not without challenges. Near the top of the list is the requirement for a large on-to-off current ratio for the OFET and small dark current in the OPD to insure high sensitivity for the detector.

The second application discussed was large-area displays. To relax the initial requirements on the OFETs, it was suggested to start with displays showing fixed format graphics and then moving to full motion video. To reduce the effect of OLED degradation over time one could use OPDs to sense the light intensity at each pixel and use off-display silicon circuits to feed the corrected information back to the OFET drivers. This application would take advantage of all three devices in an integrated process flow.

The last application centered on distributed sensors that would make use of the chemical sensitivity of organic technology. These sensors could be applied to environmental monitoring, threat detection, and a variety of medical applications. The addition of RF communication on these sensors will certainly challenge the device characteristics of OFETs.

One of the main results of this workshop was a clear understanding among the participants of the progress that has been made and the challenges in applying this new technology. We are hoping to see the formation of new networks of researchers who can continue the dialogue as this technology emerges. We are aiming to develop strong interactions between organic technologists and circuit designers to enable large-scale integration of organic components for targeted applications. At the 2004 ISSCC Professor Vladimir Bulovic will present more of the results of this workshop in a special evening session on organic electronics. In addition to Bulovic’s talk attendees will also hear from researchers at Sarnoff Labs, Infineon Corporation, and Sony Corporation. Please join us for this special session and join in the dialogue in driving organic electronics to a commercially viable technology.

Charles G. Sodini
SSCS President 2001–2003
sodini@mtl.mit.edu

Vladimir Bulovic
MIT
bulovic@mit.edu