Polymer Organic Light Emitting Diode Materials and Techniques - Research Paper Example

 Polymer Organic Light Emitting Diode Materials and Techniques Abstract The study that was conducted is about the one of the most important technology in optics and optical engineering. This is the light technology that uses semi-conducting diodes referred to as LEDs or light-emitting diodes. The main focus is one of the types of LEDs which is the polymer organic light-emitting diode (POLED) or the polymer light-emitting diode (PLED). The objective of the research was achieved through the assimilation of the published reports and developments on the topic covered by the period starting from the year 1998 to the present year. The general characterization of the POLED is also undertaken including the main theory of application, and the disadvantages and advantages of the utilization of the said technology. Introduction In the continuously improving and modernizing technological world, one technological discovery is making an important path and giving important contribution in the field of optics. In general, the semi-conducting light-emitting diodes, also referred to as LED, had found vital applications in different technologies through the industrial and modern world. LEDs A light-emitting diode can be defined as a semi-conducting diode, which is a form of electronic device that can be considered to maximize the flow of electricity that is flowing through the material and restricting its flow in the other direction such that energy is built up and causes the material to emit light energy. LED can be considered as the general type of diodes that consequently emit light energy. There are different forms of LED (Zheludev 189). A LED can be considered comparatively of more use that other light technology is that it is considered safer on the basis that the main application uses light energy emitting material. This can be attributed to the fact that other forms of light technology through the use of the flow of electric current can be considered more advantageous, often referred to as electroluminescence, which is the basic principle used in LED. Compared to the light technology that uses incandescence, which a process of achieving visible light through electromagnetic radiation (Schubert 1). Due to the said advantage of the technology referred to as LED, the application of the said technology can be considered to continuously increase and improve. In fact the application in technology and other sciences can be considered as widespread. It can be perceived through the different light technologies that are classified as LEDs such as infrared, visible-spectrum, ultraviolet, and white LEDs made from III-V semiconductors. POLED Included in the main types of LEDs is the polymer organic light-emitting diode, referred to as the POLED. The study on POLED can be considered as one of the main area of interest in terms of the types of LEDs. This can be attributed to the fact that the materials used as a semiconductor are organic materials that can conventionally be described for insulation. The application of organic materials for electric purposes can be considered as a relatively new technology since it was only initiated in 1977. The historical discovery of effect of halogen on the electrical conductivity of a polymer paved the way for the continuously growing field of discipline that involves POLEDs (Fung, Lee and Lee 181). Objective of the Study The background information regarding POLED can be considered as one of the reasons that generated the study and attention to the said area in optics. In relation to the increasing assimilated knowledge on the POLED as well as the application and utilization, the study was conducted to be able to present a descriptive and comprehensive presentation of the development of the POLED technology. On the basis of the aim for the public to gain understanding on the application of LED technology, the theory of application is also one of the most important part of the research. Also, the evolution of the POLED technology was studied and observed from 1998 to the present to be able to determine the maximization of the technology which can also be related to the to advances on the said technology. The Main Theory Applied in POLED Technology POLED is a type of LED that uses the unique polymer material for the semi-conducting purpose, thus, it can be considered to employ the same practical principles. The uses and application of the said devices can be attributed to the components and the functions. Parts of a POLED A POLED is composed of the basic LED parts that can be considered vital to the system. These parts contribute to the role of the diode when connected to an electric circuit. Due to the said capability, these LEDs are commonly used as indicators if the system if working or powered on. The important parts include the LED chip that can be considered as the main part that is using the light emitting properties; the reflector; the flat side and the charged wires with the positive and the negative terminals (Wyckoff). (Source: Wyckoff; Saini 225). Figure 1. Parts of a POLED The terminals, namely the positive and the negative sides determine the connection of the POLED to the system. One of the main characteristics of the POLED is the charge due to the role that it can play in the system. It can be recognized through the shape and length of the wire. The flat side of the bulb is an indicator of the negative port. Another way of determining the negative side is through the wire that protrudes from the POLED which is comparatively shorter than the positively charged area. It is important to consider that the negative port is connected to the negative terminal of the battery (van de Biggelaar 136). Primarily the main consideration in the establishment of the POLED is the semi-conductor chip. This is the part wherein the polymer organic material is used for the POLED and other forms of semi-conducting materials for other types of LEDs. As the whole diode, it is also composed of a positive and a negative region which is divided by the junction to be able to separate the differences in charges (Saini 225). Source: (Wyckoff). Figure 2. Parts of a POLED semi-conducting chip: the p and n regions. The positive section is represented by the p region due to the presence of positive electrical charges while the negative area is the n region that contains negative charges only. To be able to prevent flow of the said charges, an entity is used to separate the two regions of varying charges, referred to as the junction (Saini 225). Source: (Antoniadis, van de Biggelaar). Figure 3. Parts of an OLED display. The main mechanism of action then is the passage of charges through the junction to be able to react with the opposite charges. This is achieved through the induction of a right amount of electricity. If charges pass the junction, light emission occurs. The organic polymer, then, can be perceived as a barrier between the areas of positive charges (anode) and the area of negative charges (anode). The flow of electricity causes disturbance that makes the charges meet. In the said process, the polymer then emits light (Antoniadis; Leising 76). In POLED and OLED the most significant part and feature are the emissive layer which is uniquely make up of the organic materials. These are polymers of varying characteristics for POLED and small molecules for other types of OLED. The properties of the said layer are responsible for the electroluminescence and light-emission capabilities of the system. It is important to consider that there are different types of polymers that are utilized in the system (Saini 225). The conducting polymers are exemplified by polyaniline (PANI:PSS) and polyethylenedioxythiophene (PDOT:PSS). On the other hand, emissive polymers consist of the polyphenylenevinylene (R-PPV) and polyfluorene (PF). Conducting Polymers Emissive Polymers In terms of the color, the polymer can also be classified due to the color that they can emit. Blue light (e.g. PPP): Green light (e.g. PPV): Red light (e.g. PT or CN-PPV): Source: (Antoniadis; Saini 225). The properties of these bands of lights was measured through emitting assist (EA) dopant to be able to achieve better emission, high stability and luminescence efficiency. This can be achieved through co-doping (Kanno, Hamada and Takahashi 30) The Mechanism of Light Emission One of the most important considerations in the study of the POLED technology is the mechanism of emitting light. This can be attributed to the fact that the main objective in the development and discovery of the said technology is the achievement of a system that can generate sustainable light energy at low energy cost (Saini 225). Upon the study of the parts of the POLED system, the main mechanism can be presented by the diagram (Figure 4) that presents the different layers of the diode as well as the nature of their charges. Source: (Antoniadis). Figure 4. Mechanism of light emission. The main mechanism in light emission involves the action of the different layers and parts. Primarily activation is undertaken when electrical current runs through the system. On the onset of process electrons are introduces to the system specifically the cathode triggering action of the components. After that holes are infused to the anode of the system and the emission process can be observed through the action of the radiation from the electron hole and the polymer (van de Biggelaar 138). Source: (Antoniadis; Saini 225). Figure 5. The specific components of the POLED. One of the most important features of the OLED, specifically that of polymer nature, is the fact that it can emit a variety of colors ranging through the spectrum of red, green and blue on the basis of the molecular component of the polymer. The range of color can be classified on the basis of chromaticity which is presented on the diagram (Cina 221). Source: (Antoniadis). Figure 6. The diagram of chromaticity. Upon the determination of the different components of the POLED system, it is important to consider the development and discovery of the different parts to be able to appreciate the function of the said element. The Chemistry Involved in the Emission of Light from POLEDs The organic emitter layer is a key material in the chemical process. The semiconducting layer should include conjugated π-bond material which can either be a polymer (POLEDs) or a tiny molecule in crystalline phase (SMOLEDs). We shall focus on the use of POLEDs as the organic emitter. A thin two-layer polymer film inserted between two electrodes comprises POLEDs. The bi-layer polymer film includes an emitting layer, as polyfluoriene or polyparaphenylene, on top of a conducting layer, such as the polyaniline and polystyrenesulfonate combination, or the polystyrenesulfonate and polyethylenedioxythiopine combination. POLEDs are deposited on flexible substrates due to the metals and semiconductors’ electrical properties combining with the polymers’ mechanical properties (Borchardt). Organic LEDs have multilayer structures that outwardly resemble the inorganic LEDs. Light is generated when a positive bias is applied to the device thus allowing the holes and electrons to recombine in an emission layer. In POLEDs, the cathode directly injects the electrons into the emission layer and the anode injects holes through the hole transport layer. The light which is emitted becomes apparent through the transparent anode that is deposited in the glass substrate (Hecht). POLEDs contain an anode, a cathode, an emissive layer, and a conductive layer. The small molecule OLEDs or SMOLEDs on the other hand have two other parts aside from the parts mentioned in polymer: a hole transport layer and an electron transport layer. The processes involved in POLEDs only require low-temperature formation, and can be generated using ink-jet printing. This is opposed to the requirement of high temperature for chemical vapor deposition in the SMOLEDs. The hole-electron pairs which were recombined called the excitons transfer their energy to the dopants which emit light, in the emission layer. The exciton spin determines the formation of exciton. A singlet state or spin-zero forms one-quarter of excitons and a triplet state or spin-one forms three-quarters. Flourescent dyes can only change the singlet states’ energy into photons, while a photon cannot be emitted by a triple state to drop into a singlet state, so the dissipation as heat is needed by the energy. Electrophosphorescence is an alternative where molecules which contain heavy metal like platinum gain energy from singlet and triplet states, and then hold it until the states mix together and energy is converted into photons (Hecht). Cross-linking Techniques used in the Manufacturing Process The main part of manufacturing OLEDs is the application of the organic layers to the substrate and there are three ways of application: Vacuum thermal evaporation (VTE) or vacuum deposition, organic vapor phase deposition (OVPD), and the inkjet printing. Vacuum thermal evaporation is done in a vacuum chamber where organic molecules are evaporated and made to condense as thin films on cooled substrates. Organic vapor phase deposition is done in a hot-walled reactor chamber with low pressure wherein organic molecules that are evaporated are transported by a carrier gas to the cooled substrates where they condense into thin films while Inkjet printing is done by spraying OLEDs on substrates (Freudenrich). In the manufacturing of POLEDs, the more commonly used technique is solution-processing which has been considered less efficient than SMOLEDs because the required multilayer structure that makes it efficient is hard to produce. The first layer usually dissolves when the second layer is deposited. To overcome this problem, polymers which can be cross-linked by using UV radiation prior to being deposited in the next layer were developed. Through this procedure, the layers become insoluble thus allowing them to function as hole injectors as well as electron blockers. . Source: (Anscombe) Figure 7. The cross-linked layers Chemistry based on oxetane functions were developed to attain the cross-linking of the layers. In the presentation of the process, four layers were deposited from solution on top of an ITO substrate. These layers included a hole-injection layer which was water soluble, two hole transport layers that were cross-linked, and a polymer host which was doped with a phosphorescent iridium dye (Anscombe). Thermal evaporation of the CsF/Al cathode completed the emitters. The product however is still considered low in lifetime which is attributed to the compounds’ electrochemical stability. Polymers which are soluble can be made insoluble through thermal cross-linking or photo-cross-linking reactions. The Photo-cross-linking technique is commonly used in the casting industry and is likewise use in photo-resist technology. It can also be employed for photo patterning of pixels. In recent developments, low molecular weight glass compounds, photo-cross-linkable side-chain polymers, and thermally cross-linkable polymers and oligomers have been accounted for OLEDs (Ya-Dong Zhang). Screen printing and ink jetting are two common printing techniques which have technical difficulties. The technical problems are limited resolution for screen printing and wetting problems for ink jetting which often require pre-treating the substrates. A solution is demonstrated with the use of a new class of EL polymers which has the same application as a standard photoresist. Photochemical cross-linking was done to soluble polymers and oxetane sidegroups to produce polymer networks in preferred areas. These polymer networks are insoluble. The resolution of the procedure is adequate to make common pixilated matrix displays. Depositing the three colors successively produced an efficient RGB device which can be compared to advanced EL polymers. It likewise slightly decreased onset voltages, and enhanced efficiencies at high luminance levels. Improving the morphological and thermal stability guarantees improved performance in passive-matrix displays which entails high drive currents. This new technique paves the way for the efficient manufacturing of multi-color polymer based displays with high resolution, on big area via common lithography techniques (Muller, Reckefuss and Rudati). The Application of the POLED Technology The development of the different technologies that are related to POLED and LED can be perceived as one of the most colorful and active development since the said technology has its application in the present era, including the display systems of computers and other appliances. The turn of the century marks the most active development of the LED technology. The important events are summarized in the Table 1 which includes the trend in 1996, the onset of the LED and OLED technology to the present. It can then be considered that the application of the system can presently be considered as highly prevalent and extensive since almost every industry can apply the POLED display and other form of the said system (Saini 225). Table 1. The Highlights of the LED and POLED Technology through the Course of History. Source: (OLED-info.com; Saini 225). Date Historical Event 1996 ♦ CDT gives world's first public demonstration of Light Emitting Polymer devices 1997 ♦ UDC Demonstrates Flexible Flat Panel Display Technology ♦ Pioneer Electronic Produces EL Display with 260,000 Colors 1998 ♦ Kodak, Sanyo Show Full-Color Active Matrix Organic Display; First Color OEL Display Increases Threat to LCD Display Dominance ♦ Green Organic LED Shows High Efficiency 2000 ♦ Ritek plans to mass produce OLED ♦ Toshiba Corp. plans to produce (organic EL) panels in 2001 ♦ Motorola Grants OLED Technology Rights To Universal Display And Takes Equity Position ♦ UDC and PPG Industries Form Strategic Alliance for Development & Supply of Chemicals for OLED Manufacturers ♦ Sanyo Electric to start mass production of color organic EL panels in 2001 ♦ NEC, Samsung To Develop Organic Wireless Displays ♦ LG Electronics develops organic EL displays for mobile gadgets 2001 February ♦ Sony Develops World's Largest Full Color OLED (13 inches diagonally with a resolution of 800x600 pixels.) April ♦ Universal Display Corporation and Sony Corporation Announce Joint Development Agreement Aimed at OLED Television Monitors. ♦ Samsung Exhibits Color Organic EL LCD Panel for Mobile Phones at CeBIT (132 by 162 pixels). May ♦ Toshiba Develops World's First 260,000-Color Polymer OLED. August ♦ eMagin's OLED Microdisplay Selected by Air Force for F15E Aircraft. October ♦ Sony Demonstrates 13-Inch, Full-Color OLED Prototype. ♦ Universal Display Corporation and Samsung SDI Announce Key Joint Development Agreement. ♦ Universal Display Reports New Red Phosphorescent OLED Materials, Significant Power Efficiency Advances. ♦ Samsung SDI Develops World's Largest Organic Display Panel (15.1 inch). November ♦ RiTdisplay opens new color OLED/PLED factory. 2002 February ♦ Samsung SDI develops 2.2-inch AM OLED for mobile phones. April ♦ Philips Announces Industry's First Volume Shipments of Polymer-Based OLED Modules. May ♦ Kodak Announces Availability of Evaluation Kit For Active-Matrix OLED Display. ♦ RiTdisplay reportedly receives orders for over one million mobile phone OLEDs. June ♦ AU Optronics develops world's first OLED prototype combining a-Si TFT LCD technology. ♦ Epson, CDT form polymer OLED production venture. November ♦ Pioneer Supplies OLED to LG Electronics for Cell Phones. December ♦ DuPont Displays and Universal Display Corporation Form Strategic Alliance to Develop Next Generation Displays Combining Aspects of Small Molecule and Polymer OLEDs. 2003 January ♦ Philips invents EL material to generate both red and green light. ♦ Kodak, Sanyo invest in active-matrix OLED production. ♦ Sanyo Unveils Mobile Phone with Organic EL Panel Designed for KDDI, announces plans to build full-color OLED production line. February ♦ RiTdisplay lands mobile phone OLED orders from Samsung and LGE. ♦ Kodak Licenses Samsung NEC Mobile Display to Manufacture Passive-Matrix OLED Displays. March ♦ Kodak introduces the first digital camera with an OLED screen - the Kodak EasyShare LS633. ♦ IDTech develops 20-inch full-color OLED display. April ♦ DuPont forges 'Olight' brand for emerging OLEDs. ♦ Sony testing 24-inch OLED screen. May ♦ AUO and UDC develop 4-inch, a-Si TFT backplane-based, red phosphorescent AMOLED. ♦ Samsung NEC develops 65,000-color PM OLED mobile phone display. ♦ Sony demonstrated a 24.2 inch OLED panel. June ♦ ERSO and Windell develop 10-inch LTPS TFT technology-based AM OLED display. ♦ Sony to invest nine billion yen to build OLED production line. September ♦ AU Optronics has showcased its 1.93" AMOLED for Mobile Phone. ♦ Princeton electrical engineers have invented a technique for making Organic Solar Cells that Could Lead To Widespread Use Of Solar Power. October ♦ Sanyo Unveils Long-Lasting QVGA Organic EL Panel for Cell Phones. ♦ Univision begins OLED production. November ♦ Tohoku Pioneer Corporation to Be First Manufacturer to Use Universal Display Corporation's PHOLED Material in a Commercial OLED Display. ♦ Univision showcases 65,000-color mobile phone OLED sub-display. December ♦ Univision reaches monthly capacity of 6,000 OLED substrates. ♦ Casio Ventures into Organic EL Panels Driven by Amorphous Si TFT. 2004 January ♦ Opto Tech to invest NT$4.5 billion in four new OLED lines in 2004. February ♦ Philips 639 mobile phone applies PolyLED technology in unique 'Magic Mirror' display. March ♦ GE Global Research Breaks Two World Records For OLEDs As A Lighting Device. Demo Lighting Panel is Biggest and Most Efficient Ever Created. ♦ NEC drops its OLED business . ♦ Chi Mei Optoelectronics Corp. (CMO) has announced a fully functional prototype of a 20-inch full-color OLED display - the largest Amorpheous Si TFT. April ♦ Teco Optronics to invest NT$300 million to build new PM OLED plant. ♦ RiT Display ships mobile phone OLED sub-displays to Samsung, says paper. ♦ Seiko Epson Reveals 12.5-Inch Organic EL Panel for Large TVs. ♦ RiT Display shipping OLED panels to Motorola. May ♦ Seiko Epson unveils first 40" colour OLED display. ♦ Universal Display Corporation Announces Record-Breaking Power Efficiencies for its Phosphorescent White OLED Technology. ♦ Taiwan's AU Begins Mass Production of Organic EL Panels. ♦ Universal Display Corporation Unveils Ground breaking flexible OLED Prototype on Metallic Substrate. June ♦ Toppan to volume produce large-size OLED panels. ♦ OLED-Info is on-line, the web's first OLED community site. September ♦ Sony Starts Mass Production of Organic EL Displays, and released first a new clie PDA with a 3.8in 480 x 320 OLED screen. October ♦ LG.Philips develops 20-inch OLED display. November ♦ OLED displays with 50,000h operating lifespan from URT. ♦ Seiko Epson will commercialize OLED TVs by 2007. December ♦ CDT IPOs, lists on NASDAQ. 2005 January ♦ Samsung Electronics develops 21-inch OLED for TVs, claims world's largest. ♦ Samsung SDI To double the OLED output. ♦ OLED Technology Poised to Become Core Business for Daewoo Electronics. February ♦ MP3-player demand boosts sales of Taiwan OLED makers. ♦ LG.Philips LCD launches AM OLED Business. March ♦ Sony introduces Flash based MP3 players with OLED display. ♦ Canon says to start making OLED displays next year. April ♦ Samsung Licenses OLED Patents from Universal Display. May ♦ Kodak Licenses OLED Technology to Fuji Electric Holdings. ♦ CDT Achieves 100,000 Hour Blue Polymer Lifetime. ♦ Samsung Electronics Develops World's First 40-inch a-Si-based OLED. June ♦ UDC announces fundamental breakthrough in blue PHOLEDs - New sky blue achieves over 15,000 hours of lifetime. July ♦ Samsung SDI to invest over 850M$ in AMOLED production. August ♦ LG Electronics Launches Full-Scale OLED Operations. September ♦ Toppoly develops a 7" AMOLED display. October ♦ Samsung SDI's Organic LED Display Shipments Top 30 Million units. November ♦ CDT Prints a 14" P-OLED display. ♦ China's first OLED production line set up. December ♦ Pioneer withdraws from AM-OLED market. 2006 January ♦ BenQ announces a camera and a phone with large (2.0") OLED screens. ♦ Kodak Broadens its Participation in OLED Technology, ends OLED joint venture with Sanyo. March ♦ Univision to invest $40M in OLED line expansion. ♦ Epson and CDT shows world's first print head using an OLED light source. April ♦ Kodak Licenses OLED Technology to Univision Technology. May ♦ Pioneer Launches Mass Production at White OLED Plant. June ♦ India's Samtel to produce OLED displays. August ♦ AUO relocates OLED engineers, focuses on LCD. September ♦ first 'Nokia' phone with an OLED display. ♦ CDT sees rapid progress in Blue and Red lifetime October ♦ CMEL & CMO develop 25" AMOLED TV panel ♦ Samsung showcases 17" AMOLED 2007 January ♦ Sony showcases 27" and 11" OLED TVs at CES. Says might start production at 2008. February ♦ Sony begins production of AMOLED panels. March ♦ KDDI starts selling a phone with a 2.4" AMOLED display. ♦ Konica Minolta and GE to jointly develop OLED light products. April ♦ Sony to sell 11" OLED TVs in 2007 ♦ TMDisplay to sell 21" OLED TVs in 2009 ♦ Toshiba plans to launch 30" OLED TVs in 2009 May ♦ Samsung SDI to make OLED TVs in 2009 ♦ Mitsubishi to enter OLED market ♦ Novaled Achieving Groundbreaking Lifetimes For fluorescent PIN OLEDs ♦ Sony shows Flexible OLEDs July ♦ LG Electronics moves into AMOLED mass production ♦ CMEL sampling 2.4" AMOLED panels ♦ Sumitomo acquires CDT for 285M$ August ♦ Sumitomo plans OLED TVs by 2009 Source: (OLED-info.com; Saini 225). Based on the presented evolution and development of different systems and technologies, it can be considered that the application of POLED can be recognized in different field of application e.g. medicine, academe, industries and even defense. It is also used in different gadgets and appliances, from tools and machineries to computers and automated equipments and apparatus. Upon consideration, it can be perceived that at the present point in history the extensive utilization of POLED can classify the technology as a necessity for establishment of different systems. Namely, the system can be utilized in television screens, computers, portable systems, and advertising. Illumination is also one of the basic applications. Analysis Based on the presented notions, it is still vital to analytically deliberate the possible applications of POLED. In relation to this, the determination of the advantages and the drawbacks are important and can be considered essential to the process. Advantages There are different notions that can be considered in the positive side of the issue. One is the fact that the use of materials for conductivity is not limited to metals. For that matter the cost can be considered as less. This can be attributed to the cost-effective notion which can be considered as one of the most important factor in the study of any method or technology that will be released in the market. Aside from the material, cost-efficiency can also be described by the main feature of the POLED system. It is the generation of a bright light through the use of the minimum amount of input energy. For that matter maximization of energy consumption can be achieved (Saini 226). Also related to the unique features of the system is the capability for a wide range of color display. Based on studies too, lower costs can be incurred compared to LCD and plasma display. The processing of the OLED solution can be considered as being cost effective also due to the fact that the fabrication cost is lower. Another reason is low solution processing cost. Other advantages include high brightness, near-perfect viewing angle and high rate of response time (van de Biggelaar 134). One of the most unique features of the POLED or OLED is the capability to be printed to surfaces. This is on the basis of the structure and the use of organic polymers. Based on the flexibility of the system it can also be printed on shirts and roll up banners. In terms of illumination, the light emitted has higher quality aside from the fact that it is composed of a variety of colors. Also in terms of display, POLED does not require a backlight function, to the fact that it has a built in light source (Leising 76). Disadvantages and Limitations Another important consideration in the feasibility of application of the craft is the negative effects and limitations. It can be considered that the main strength of the system is also the main weakness. Since the system uses organic materials, degradation is the main hindrance in the main stream application of the POLED (Saini 227). Another is the considerably short lifespan that can be around 5000 hours of display only. This is less than 10% of the lifespan of display using other materials. Conclusion Based on the study conducted, the importance of the discovery and development of the LED technology can be presented through a variety of fields and application. The development of this class of technology can be considered as continuously progressing. This can be attributed to the fact that every component can be improved and developed. The fields related to LED technology and development include, flat- and LCD panel displays which contains the light valve and the emissive type. The Small Molecule and the Coagulated Polymer can be considered as one of the major line of future research and experiments related to OLED (Saini 225). References Andrew, Piers et al. “Photonic band structure and emission characteristics of a metal-backed polymeric distributed feedback laser.” Organic Photonic Materials and Devices IV. Eds. Bernard Kippelen and Donal D. C.Bradley, 13 June 2002. 71-78 Anscombe, Nadya. "Polymer OLEDs Match Small-Molecule Efficiencies." Jul 2006. Photonics. 11 Oct 2007 . Antoniadis, Homer. Overview of OLED Display Technology. OSRAM Opto Semiconductors OLED Product Development, 2003. Bernius, Mark T. “Developmental progress of electroluminescent polymeric materials and devices.” Organic Light-Emitting Materials and Devices III. Ed. Zakya H. Kafafi, Editors, 17 December 1999. 129-137 Bockstaele, Ronny et al. Microcavity LED-based parallel data link using small-diameter (125 m) plastic optical fibres. J. Opt. A: Pure Appl. Opt. 1 (1999): 233-236. Borchardt, John K. "Developments in organic displays ." 12 Oct 2004. Science Direct. 11 Oct 2007 < http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6X1J-4DHWPG9-2X&_user=10&_coverDate=09%2F01%2F2004&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=47c45ba26148347addc9c1f3b76061ec>. Chen-Morris, Raz D. “Optics, imagination, and the construction of scientific observation in Kepler's new science.” The Monist, October, 2001. Chuang, T. K. et al. “Active-matrix organic light-emitting displays on flexible metal foils.” Cockpit and Future Displays for Defense and Security. Eds. Darrel G. Hopper, Eric W. Forsythe, David C. Morton, Charles E. Bradford, Henry J. Girolamo, 25 May 2005. 234-248. Cina, Savatore et al. “New efficient light-emitting polymer diode for flat-panel display applications.” Organic Photonic Materials and Devices III. Ed. Bernard Kippelen and Donal D. C.Bradley, 15 June 2001. 221-228. Czerw, Richard et al. “Tailoring hole transport and color tunability in organic light-emitting devices using single-wall carbon nanotubes.” BioMEMS and Smart Nanostructures. Eds. Laszlo B. Kish, Erol C. Harvey and William B. Spillman, 19 November 2001. 153-161 Freudenrich, Craig. "How OLEDs Work." How Stuff Works. 11 Oct 2007 . Fung, Man-Keung, Chun-Sing Lee, and Shuit-Tong Lee. “Metal/Polymer Interface for Organic Light-Emitting Devices.” Organic Light Emitting Devices. Ed. Klaus Mullen and Ullrich Scherf. Wiley-VCH, 2006. 181-212. Hecht, Jeff. City of Light: The Story of Fiber Optics. New York: Oxford University Press, 2004. Hecht, Jeff. "PHOTONIC FRONTIERS: ORGANIC OPTOELECTRONICS - Organic LEDs try to live up to a bright promise." 1 Jan 2007. Laser Focus World. 11 Oct 2007 . Huang, Jen-Wei and Shih Jung Bai. “Light-emitting diode of fully conjugated heterocyclic aromatic rigid-rod polymer doped with multi-wall carbon nanotube.” Light-Emitting Diodes: Research, Manufacturing, and Applications IX. Eds. Steve A. Stockman and H. Walter Yao, E. Fred Schubert, 7 March 2005. 154-161. Hubert, Christophe et al. “Emission properties of organic light-emitting diodes directly patterned using optically controlled nanostructuration means.” Organic Optoelectronics and Photonics. Eds. Paul L. Heremans, Michele Muccini and Hans Hofstraat, 8 September 2004. 441-448. Kajii, H. T. “Organic photonic devices utilizing nano-structured materials.” Quantum Sensing and Nanophotonic Devices III. Eds. Manijeh Razeghi and Gail J. Brown, 28 February 2006. Kamaev, Vladimir et al. “Optical studies of 2D and 3D metallo-dielectric photonic crystals.” Plasmonics: Metallic Nanostructures and Their Optical Properties III. Ed. Mark I. Stockman, 26 August 2005. Kanno, H., Y. Hamada and H. Takahashi. “Development of OLED with high stability and luminance efficiency by co-doping methods for full color displays.” IEEE Journal of Selected Topics in Quantum Electronics 10.1 (Jan.-Feb. 2004): 30 – 36. Kim, W. H. et al. “Molecular organic light-emitting diodes using highly conductive and transparent polymeric anodes.” Organic Light-Emitting Materials and Devices V. Ed. Zakya H. Kafafi, 27 February 2002. 85-92. Leising, Guenther. “Efficient full-color electroluminescence and stimulated emission with polyphenylenes.” Organic Light-Emitting Materials and Devices II. Ed. Zakya H. Kafafi, 16 December 1998. 76-87. Muller, C. David, et al. "Multicolor polymeric OLEDs by solution processing." Feb 2004. SPIE Digital Library. 11 Oct 2007 . OLED-info.com. OLED History. 09 November 2006. 02 October 2007 . Ryszard R. Buczynski et al. “Polymer-based pixel matrix display in MOEMS technology.” MEMS, MOEMS, and Micromachining. Eds. Hakan Urey and Ayman El-Fatatry, 16 August 2004. 36-43. Saini, Gurdial S. and Darrel G. Hopper. “Approach of organic light-emitting displays (OLED) to technology status.” Cockpit Displays V: Displays for Defense Applications. Ed. Darrel G. Hopper, 14 September 1998. 288-298. Saini, Gurdial S. “Update of status of OLED technology.” Cockpit Displays VI: Displays for Defense Applications. Ed. Darrel G. Hopper, 16 August 1999. 225-235. Schubert, E. Fred. Light-Emitting Diodes. 2nd ed. New York: Cambridge University, 2006. van de Biggelaar, Ton et al. “Passive and active matrix addressed polymer light-emitting diode displays.” Flat Panel Display Technology and Display Metrology II. Ed. Edward F. Kelley and Apostolos T. Voutsas, 30 April 2001. 134-146. Wirth, R. et al. “Fast LEDs for polymer optical fiber communication at 650nm.” Optoelectronic Devices: Physics, Fabrication, and Application II. Ed. Joachim Piprek, 25 October 2005. Wyckoff, Susan. Experiments by Exploration. 22 Feb 1999. Arizona State University. 01 October 2007 Ya-Dong Zhang, Richard D. Hreha, Ghassan E, Jabbour, Bernard Kippelen, N. Peyghambarian, Seth R. Marder. "Photo crosslinkable polymers as hole transport materials for organic light-emitting diodes." 3 May 2002. Royal Society of Chemistry. 11 Oct 2007 . Zheludev, Nikolay. “The life and times of the LED – a 100-year history.” Nature Photonics 1.4 (2007): 189-192. Zweben, Carl H. “New material options for light-emitting diode packaging.” Light-Emitting Diodes: Research, Manufacturing, and Applications VIII. Eds. Steve A. Stockman, H. Walter Yao and E. Fred Schubert, 21 June 2004. 173-182. Read More