Organic Electronics — From Materials to Applications

Abstract

This Organic Electronics Special Issue of Advanced Materials is dedicated to reviewing the current status of the science underpinning the main and emerging applications for this exciting technology. It contains a comprehensive series of invited reviews, progress reports, and research news articles that highlight the breadth in scope of this multidisciplinary area. Contributions from world class research groups spanning the globe showcase the spectrum of research and development in this field, from initial research phases through to the most recent advances in applications and opportunities for future exploitation. Advances in organic light-emitting diodes (OLEDs) continue at an accelerating pace. There are now many highperformance OLED displays in products from televisions to mobile phones, while several companies are poised to launch organic lighting products. Although most of these OLED products are currently fabricated from vacuum or vapor deposition techniques, solution deposition based on higher throughput printing is also making serious advances in both displays and lighting. Central to these advances are a fundamental understanding of the mechanisms responsible for degradation in luminescence over continued operation. This is discussed in detail in the progress report of So et al. Active matrix electrophoretic displays for ebook and handheld mobile applications, driven by organic transistors, have been demonstrated by several organizations recently, with the first commercial ebook product by Plastic Logic soon available through advanced orders. Advances in transistor performance have been facilitated by significant leaps in semiconductor physics and chemistry. Insights into the nature of charge transport physics at the semiconductor-dielectric interface provide guidance for both materials design and device architecture, and are described in the research news article by Sirringhaus et al. Until very recently, the charge carrier mobilities of electron transport materials have significantly lagged behind their hole-transporting counterparts. This has impeded development of organic CMOS logic circuitry and the lack of development in this area has restricted the range of acceptor materials available for organic bulk heterojunction solar cells. There are, however, many promising new materials classes that have recently demonstrated high potential, and these are reviewed in the article by Anthony, Facchetti, Heeney, Marder, and Zhan. Improvements in thin film semiconductor performance can be not only attributed to advances in molecular design concepts, but also to improved understanding of material assembly into highly ordered microstructures on deposition. Although solution deposition is typically a kinetically driven, chaotic process, there are many underpinning thermodynamic principles that can be used to optimize surface energies, crystallization processes, and thermal behavior. These are reviewed, along with small molecule vapor deposition, with an emphasis on their impact on fabricating optimally organized and aligned semiconductor thin films, in the article by Bao, Stingelin, et al. Accurate characterization of the thin film morphology is crucial in developing the structure/property relationships that advance molecular design and validate the material science employed to optimally fabricate the semiconductor films used in devices. The correlation of charge transport with thin film microstructure and the impact of processing conditions can be elucidated through spectroscopic techniques, and is reviewed in the article by Salleo et al. The applied nature of organic electronics is well represented in this special edition. With the impending launch of the first application utilizing organic transistors, it is timely that the article by Anthopoulos et al. reviews the latest developments of organic-transistor-driven active matrix backplanes for both electrophoretic and OLED displays. This review also covers advances in organic circuitry for microelectronics, demonstrating that we are primed for a new wave of impending applications with widespread utility. Following closely behind, is the development of organic solar cells. Photovoltaic devices have made large improvements in performance recently, now reaching over 8% power conversion efficiencies for a poly mer light-absorbing donor, fullerene electron acceptor bulk heterojunction device. In the article by Brabec, Gowrisanker, Halls, et al., a review of materials development, device optimization and lifetime studies has been undertaken, with a strong industrial focus. Finally, an exciting attribute of organic electronics is that with the creative science that is possible, new applications and opportunities will inevitably arise. One promising such application is in the field of sensing. Although this area is not as advanced as others described in this issue, there is considerable scope to detect not only molecules, but also sense environmental conditions and light. These concepts are reviewed in detail in the article by Katz et al.