An Overview of Latest Display Technologies and Their Usage for Various Special Applications

Home , AMOLED, Digital Light Processing, Quantum dot display

Journal of Radio and Television Broadcast Volume 3 Issue 3

An Overview of Latest Display Technologies and their Usage for Various Special Applications

1Dr. Vandana Khare, 2N. K. Shreyas 1Professor, Department of Electronics and Communication Engineering, CMR College of Engineering & Technology, Hyderabad, India 1Research Scholar, Department of Electronics and Communication Engineering, JNT University, Hyderabad, India 2B. tech II year, Department of Electronics and Communication Engineering, CMR College of Engineering & Technology, Hyderabad, India Email: [email protected], [email protected]

Abstract In the new world of technology, due to its volatile nature there had been immense changes in the display technology since the past few years. Now it is that when portability plays an important role, the electronic displays of various electronic devices have changed their trend from being heavy and thicker in size to more light and thin in dimensions. This significant change in the dimensions of the electronic displays is due the adoption of AMOLED and Active QLED technology. AMOLED [Active Matrix Organic Light Emitting Diode] is a display technology used in smartphones, mobile devices, laptops and television. A Quantum Dot Display is a display device that uses Quantum dots (QD), semiconductor nanocrystals which can produce pure monochromatic red, green, and blue light. Hence, with the use of these display technologies the manufacturing and usage of flexible and foldable electronic displays have come into existence with low power consumption and low cost, brighter colors with wide color gamut. Also by using this AMOLED and AQLED technology in the latest electronic displays, it is possible to control each and every pixel of the particular display so that, the possibility of manipulating the saturation, brightness, contrast and especially sharpness of the image or the picture increases. But still implementation of AQLED (Active Quantum Dot Display Light Emitting Diode) display is under Research and development process as there are various aspects like optimization and implementation with existing display technologies. This paper proposes a brief idea about the latest display technologies i.e., AMOLED & AQLED and their special applications in various contemporary devices and its possible usage in various other fields in modern devices.

Keywords: AMOLED, OLED, AQLED, QLED, TFT, HOMO, LUMO.

INTRODUCTION the level needed to create a constant The term AMOLED stands for Active current to the pixel, thereby eliminating Matrix Organic Light Emitting Diode. As the need for the very high currents the name suggests this technology is required for passive-matrix OLED dependent on its parent technology i.e. operation. This feature has made the OLED which uses matrix of pixels which possibility of adjusting the brightness are deposited on TFT layer by which levels, contrast levels, etc., at the pixel control of current through each individual level. pixel can be achieved. The TFT works as series of switches for completing this job. Coming to the 2nd part of display One TFT is used to start and stop the technology i.e. AQLED which stands charging of a storage capacitor and the Active Quantum Light Emitting Diode is second one to provide a voltage source at also one of the latest and upcoming trends

Journal of Radio and Television Broadcast Volume 3 Issue 3

of display technologies. In these Auxiliary technologies manufacturing of technology nano crystals of semiconductor AMOLED T.V’s are also taken into view. which serve as quantum dots helps in The authors Moon Kee Choi, Jiwoong conversion of back light into pure mono Yang, Taeghwan Hyeon & Dae-Hyeong chromatic light of red, blue and green. The Kim in their publication “Flexible difference between AQLED and quantum dot light-emitting diodes for AMOLED is that AMOLED possess self- next-generation displays”, in the year luminescence feature but the latter possess 2018 discuss about the QLED technology electro luminescence dependent feature i.e. and future scope of QLED in it depends on the backlight for production implementing flexible displays. In of display contrast with various other display technologies the AQLEDS have their In this paper, the details about the upper hand when it comes to various AMOLED technology under the electronic technical parameters such as brightness, display technologies are discussed and a wide colour gamut, low voltage brief introduction to operation of these consumption and ultrathin dimensions. display units is mentioned. The rest of the As mentioned by the authors many issues paper is organized as follows: Section II like cutting edge quantum dot gives the details about the related work. technology, flexible and wearable QLED The detail about the existing technology in and colour patterning are discussed. electronic displays is mentioned in Section III. The complete details about the EXISTING TECHNOLOGY proposed display technology are illustrated The following are few display in section IV. Next, Section V gives the technologies used: conclusions and future scope of this 1. Cathode ray tube display (CRT) modern technology. 2. Light emitting Diode (LED) 3. Electroluminescent display (ELD) RELATED WORK 4. Plasma Display Panel (PDP) The authors Jong hyuk Lee, Hye Dong 5. Liquid Crystal Display (LCD) Kim, Chang Ho Lee, Hyun-Joong Chung, 6. High performance Addressing Display Sung Chul Kim and Sang Soo Kim in (HPA) their publication “The Technological 7. Digital Light Processing Display Trends of Future AMOLED” ,in the year (DLP) 2009 from Technology Center, Samsung 8. Field emission display (FED) etc., Mobile Display Co, LTD ,review the technological trends for the future Introduction of each individual display AMOLED ,especially the unique technology applications to small and medium sized CRT (CATHODE RAY TUBE) Display displays as well as large sized AMOLED The cathode ray tube display uses vacuum TV. The unique characteristics of tube, phosphorescent screen and electron AMOLED enable paper thin, foldable, guns for the purpose of display. The CRT bendable and transparent displays which was basically used in oscilloscopes, old the other display technology can’t easily television’s etc. By controlling the realize. For large sized AMOLED TV, electron beam intensity which is emitted TFT backplane, color patterning and from electron gun the image can be encapsulation are the key technological produced, these beams are influenced the issues and the new technologies should be magnetic deflection which is one of the consequences of magnetic field around developed for the mass production of electronics circuits. AMOLED TV. With the aid of certain

Journal of Radio and Television Broadcast Volume 3 Issue 3

LED (LIGHT EMITTING DIODE) which can produce to a 16 million colours. DISPLAY This phenomenon is referred to as “multi The LED display is one of the commonly line addressing”. used electronic displays where in the light emitting diodes act as pixels to laminate THIN FILM TRANSISTOR (TFT) various colors of light. The LED consumes In the TFT (Thin Film Transistor) which is less power for illumination of the pixels in a kind of an FET (Field effect transistor) order to display the image. Thus they are made by deposition of layers semi- widely used in sign boards, Stage lighting, conductors and di electric over a substrate. T.V displays, Etc., The substrate is generally made out of

ELECTRO-LUMINESCENT glass but in other transistors the semi- DISPLAY (ELD) conductor material itself acts as substrate. In this display technology electro The TFT generally serves as series of luminescent material like gallium arsenide switches for making the light produced is sand witched between 2 layers of from the active region of semi-conductor conducting material which upon electrical on or off. activation produces light. ORGANIC LIGHT EMITTING PLASMA DISPLAY (PLD) DIODE (OLED) The plasmas are the electrically charged In the organic light emitting diode, the ionized gases which upon electrical electro luminescent layer is made using an activation produce visible light making it organic compound through which the light possible to use it in the displays. These is emitted with the application of electric ionised gases are placed in small cell like current. The organic compound is placed structures. between 2 electrodes with one electrode made completely transparent. The OLED LIQUID CRYSTAL DISPLAY (LCD) has been helping factor for development of The Liquid Crystal Display (LCD) is one next generation display technologies such of the flat panels’ displays which are as AMOLED. OLED’ S are basically used dependent on back light to produce images. The LCD’s are used widely in 7 in T.V, mobile display, Etc. segment displays, displays of digital clock and computer screen displays, etc. The PROPOSED AMOLED & AQLED LCD displays are the successor of the old DISPLAY TECHNOLOGIES CRT displays hence, reducing the INTRODUCTION to AMOLED dimensions both in appearance and weight. Before having an overview about LCD’s have more advantage over CRT AMOLED and AMQLED displays, it is displays with low possibility of image mandatory to have some basic information burn- in. They consume less power and its parent display technology i.e., OLED can be used efficiently for producing (ORGANIC LIGHT EMITING display. DIODE) and QLED (QUANTUM DOT DISPLAY LIGHT EMITTING DIODE) HIGH PERFORMANCE respectively.The term AMOLED stands ADDRESSING (HPA) for Active Matrix Organic Light Emitting The High-Performance Addressing display Diode. As the name suggests this is an improvement of LCD with passive technology is dependent on its parent matrix display analyzes the incoming technology i.e. OLED which uses matrix video signal and refreshes the image by of pixels which are deposited on TFT layer modulating the frequency making it the by which control of current through each high responsive rate display technology individual pixel can be achieved. The TFT

Journal of Radio and Television Broadcast Volume 3 Issue 3

works as series of switches for completing this job. One TFT is used to start and stop Materials Used the charging of a storage capacitor and the Coming to the materials used in second one to provide a voltage source at production of OLED’s much more the level needed to create a constant complex analysis of electro chemistry and current to the pixel. The OLED’S are physics is needed. Number of materials is mainly categorized depending of accessing used making of OLED for various of pixels present. If each row of pixels is internally developed functions like controlled sequentially, then these types of transport of charge. Using thermal OLED are called “PASSIVE OLED”. But evaporation process for production of coming to its counterpart i.e., ACTIVE OLED consisting of minute molecules is OLED, the electric current through each an expensive task. But when compared to individual pixel can be controlled making Polymer based display devices, the it more reliable for usage in the general vacuum deposited organic OLEDs and special applications. This mechanism facilitate the formation of Homogeneous in AMOLED of controlling each pixel has layers and multilayer structures which become possible by placing the TFT allow efficient charge exchange. Generally backplane behind the pixels with not only small molecules of Alq3 are used in allows easy switching of pixels but also OLED. If the properties of these small allows improvement of resolution and molecules are analyzed carefully then sharper images. Overcoming the production of molecule sized devices disadvantage of LCD, CRT displays etc., binding the optical, electrical properties AMOLED displays due to self-light* can be accomplished. Coming to the emitting property perform well even in design architecture of OLED layer of ambient day light than their counterparts organic material is placed between two by improving high contrast ratio of electrodes. This arrangement is placed on display. the substrate and the organic material is electrically conductive. The organic INTRODUCTION AQLED (Active material consists of High Occupied Quantum Dot LED) Molecular Orbitals and Low Unoccupied The abbreviation of AQLED is Active molecular orbitals. From cathode, Quantum Dot Light Emitting Diode. electrons are injected into LUMO region Before discussing about AQLED, a brief and holes are injected at HOMO region idea about QLED is needed. The QDLED from anode. The hole movement in OLED basically works on the principle that the is more hence, decay of excited state recombination of electron-hole from results in relaxation energy levels. The organic material takes place in Quantum recombined electron-Hole pair at the Dots thereafter emitting visible emissive region is called as EXCITON. monochromatic light of more efficiency Indium Tin oxide is generally used as reaching 100% colorgamut. When this Anode as it has high electron injection technology is collaborated with Active property at HOMO junction and is organic layer then sensitization of electric transparent to visible light since the Anode up to sub pixel level is can be achieved. in OLED are selected based on their The basic Quantum Dot structure consists chemical stability, optical transparency of Cadmium Selenide. One more added and electrical conductivity. advantage of AQLED technology is more efficient power consumption, sharper display and more vibrant colour saturation levels.

Journal of Radio and Television Broadcast Volume 3 Issue 3

middle of dopant allows transfer of singlet and triplet states by spin-orbit coupling.

Bottom or top emission The main difference between top emitted Fig: 1. Light Emitting Diodes using and bottom emitted OLED’s lies in the Polymers direction of emission of light which comes out of the device. If the light is emitted Poly (p-Phenylene vinylene) through the transparent or semi transparent In these types of diodes the light is emitted layer electrode and substrate on which the from the electroluminescent conductive panel is placed, it is called bottom polymer when an external voltage is emission. In top emission devices the light applied and the required voltage for the exits the device from the lid i.e. placed polymer LED is activate and function is during the fabrication process of the very less. These polymers LED due to device. In practice top emission devices flexible nature can be used in a wide are widely used for AMOLED displays variety of applications as their film is thin because integration of the pixels with layer. These polymers can be formed using immobile TFT back plane can be made. spin coating method. To achieve the But in bottom emissive devices the formation of multilayer polymer light blockage of light transmitted can take emitting diodes which are used in many place due to interfacing of TFT array with display applications vacuum deposition bottom substrate. method. The first Polymer Light Emitting Diode developed using Poly (p-Phenylene Transparent OLEDs vinylene). Using transparent OLED’s Top and bottom emitting TOLED’s can be made which can improve the contrast levels to have better display in day light. These transparent OLED’s use semi-transparent or transparent contacts on both sides of the device.

Graded heterojunction Fig: 2. OLED using Phosphorescent The reduction of ratio of electron-holes to materials electron transporting chemicals is made using graded hetero junction OLED’s Iridium complex Using Phosphorescent which increase the quantum efficiency of materials in OLEDs the electrical energy contemporary OLED’s to 2x times. can be efficiently converted into light energy using the principle of Electro Stacked OLEDs and Inverted OLED phosphorescence. Also the Internal Stacked OLEDs use a pixel architecture Quantum efficiency of the device is that stacks the red, green, and blue sub pixels on top of one another instead of enhanced by decay of singlet and triplet next to one another, leading to substantial exactions by usage of Electro increase in gamut and colour depth, and phosphorescence materials. In general poly greatly reducing pixel gap. Currently, N-vinyl carbazole is used as main hosting other display technologies have the RGB material. To This host material an organic (and RGBW) pixels mapped next to each metallic complex such as Iridium complex other decreasing potential resolution. In is added as a Dopant. The metal atom at contrast to the OLED in which the anode

Journal of Radio and Television Broadcast Volume 3 Issue 3

is placed on the substrate, in the inverted (luminescence) upon electrical activation OLED cathode is placed on the substrate that have been deposited or integrated onto to connect to drain end of N channel TFT a thin-film transistor (TFT) array, which basically for amorphous silicon TFT back functions as a series of switches to control plane. Using the above techniques, materials a new concept has been the current flowing to each developed which is addressing of pixels in individual pixel. The AMOLED display in the display screen. order to function, use two TFTs backplanes one for applying a proper Designing of AMOLED and AQLED voltage across the individual pixel and the display other TFT backplane for Starting and Design of AMOLED display Stopping the charging of Storage capacitor An AMOLED display consists of an active matrix of OLED pixels generating light

Fig: 3. Design of AMOLED display

Schematic of active matrix OLED Polycrystalline Silicon(Poly-Si) & A transparent substrate is used in the Amorphous Silicon(a-Si) are two generally construction of AMOLED display in order used TFT backplanes for allowing the to manufacture Flexible displays. formation of Active Matrix planes.

Fig: 4. Design of AQLED display

Journal of Radio and Television Broadcast Volume 3 Issue 3

Quantum Dot Design by Samsung solution of Quantum Dots and Organic technologies Here in the AQLED design, semiconductors are mixed with the help of the Quantum Dot nanoparticles are spin casting process. The formed arranged in from of active array of matrix monolayers of QD are placed on top of the which allows the reduction in response co-deposited contact. During the drying of time of each individual sub pixel and solvent, the formed QD layer disassembles eliminating the usage of Liquid Crystal from the Organic material and move layer. There are basically two approaches towards the surface of the film. The of the Quantum Dot. They are organic layer generally used is N,N’-Bis photoluminescent and electroluminescent (3-methylphenyl)-(N,N’- approaches. The photoluminescent approach used by all current commercially diphenylbenzidine). In phase separation available QLED displays, including process lateral patterning of different QDs Samsung’s new QLED TVs, uses an which in turn disable to form multi-colour external light to stimulate the QDs. The Quantum LEDs’. Few parameters that electroluminescent approach applies affect the formed Quantum Dot structure electricity individually to each QD to are solvent and solution concentration, deliver a self-emitting image where purity of the solvent used, QD size essentially every pixel creates its own distribution and aspect ratio etc. light. Clearly the ability of this approach to combine LCD’s brightness and color Contact printing advantages with perfect black levels makes The contact printing method is one such it a hugely exciting proposition for the method used for the formation of quantum future. The main innovative approach is dot thin films. These films are solvent free the cladding of the QDs in a new metallic water-based suspension. Using this sheath. It matters for various reasons. method, the RGB pattern of electro luminescent structure with a resolution of First, it makes the QDs much less 1000 pixels per inch can be accomplished. susceptible to oxidation, meaning that their In this process the main task lies with performance will erode much less rapidly over time than normal QDs. Second, the separating the solvent’s interaction with metal sheath means that the QDs can be the charged transport layer of quantum dot positioned differently on the preliminary LED structures. To overcome this problem display structure. the usage of solvent free suspensions is encouraged. Now the process of contact In the AQLED design ,the Quantum Dot printing is mentioned below stage by layer is placed in-between the electron and stage. hole transporting organic materials when  First Polydimethylsiloxane is moulded the electrons and holes recombine in the using a silicon master and the top side Quantum Dots they emit visible light. The of this PDMS stamp is coated with a Quantum Dot layer is generally made of thin film of chemical vapour deposited Cadmium Selenide nanocrystals. For the aromatic organic polymer. fabrication of AQLED display the two  This thin layer is inked through spin basic methods are, casting of colloidal quantum dot 1. Phase separation method suspended solution in organic solvent 2. Contact printing method and after the evaporation of the solvent the resulting single QD layer is shifted Phase separation on to the substrate using contact The Phase separation process is mainly printing. used to produce Quantum Dot monolayers  The matrix of QD’s is made by process layers of larger size. In this process the of spin casting in which the QD’s after

Journal of Radio and Television Broadcast Volume 3 Issue 3

being placed on substrate are evenly watts regardless of whatever the case spun to spread the solution. Using this might be one important features in process QLED of 25 micro meter wide AMOLED display is that the black pixels strip can be fabricated of red, green turn off completely making it produce high and blue mono layers. The main contrast levels of image produced. The advantage of this process is effective proposed QLED display also carries all the usage of QD hence reducing the advantages that an AMOLED display expenditure. does. The only difference lies in the materials used in their manufacturing. CONCLUSION Thus, in conclusion the AMOLED and AMOLED and AMQLEDS displays be AQLED display are far ahead in terms of responsible for greater refresh amounts SIZE, POWER CONSUMPTION, than passive-matrix, repeatedly decreasing COST AND ESPECIALLY DISPLAY the reply time to a smaller amount than a FEATURE. These display technologies if millisecond, and they devour considerably implemented in the latest electronic minus power. By using this property it gadgets from smartphones to smart creates active-matrix OLEDs and QLEDs watches can be made advantageous and which is well-applicable for portable more reliable to future usage. electronics, where energy feasting is dangerous near battery life. Various A FEW APPLICATIONS OF parameters such as the colour production PROPOSED DISPLAY and brightness decide the power TECHNOLOGIES IN EXISTING consumption of the display for reference ELECTRONIC DISPLAYS and OLED display (QVGA) on an average 1. Mostly used in flexible mobiles. consumptions 0.3 watts for displaying 2. Frequently used as mobile chargers. white text on black background and vice 3. Most of the time used with 60 inches versa of this consumes 0.7 watts but in Televisions. LCD’s, on and average consume 0.35 4. Generally used in smart watches.

Fig: 5. Amoled Display In Samsung’s Galaxy Note 8 Edgesamsung Flexible Mobile 7.3” Exhibited At World Mobile Congress

Fig: 6. Sony 60 inch TV using QLED display Samsung gear S Smart watch with AMOLED Display

Journal of Radio and Television Broadcast Volume 3 Issue 3

FUTURE SCOPE Symposium Digest of Technical Thus, using the above discussed Papers. technologies such as the AMOLED and 4. Hamer, John W.; Arnold, Andrew D.; AQLED displays bendable, high Boroson, Michael L.; Itoh, Masahiro; resolution, better colour saturated displays Hatwar, Tukaram K.; Helber, Margaret can be made. These displays can be used at J.; Miwa, Koichi; Levey, Charles I.; scientific research centres so that effective Long, Michael; Ludwicki, John E.; usage of space can be made. Also, 3D Scheirer, David C.; Spindler, Jeffrey stereoscopic displays that use eye tracking P.; Van Slyke, Steven A. (2008). (via stereoscopic front-facing cameras) to "System design for a wide-color-gamut provide full resolution 3D visuals can also TV-sized AMOLED display". Journal be developed. These flexible displays can of the Society for Information also be used in Defence applications and Display. Medical applications so that mobility and 5. "Introduction to OLED Displays – portability of various devices like the Design Guide for Active Matrix OLED monitoring and surveillance systems can (AMOLED) Displays". 4D Systems. be further increased. These AMOLED 6. Lin, Chih-Lung; Chen, Yung-Chih. "A screens when developed in larger Novel LTPS-TFT Pixel Circuit dimensions can be substituted with Compensating for TFT Threshold- projectors used for presentations or used in Voltage Shift and OLED Degradation movie theatres. for AMOLED". IEEE Electron Device Letters. REFERENCES 7. Sarma, Kalluri R.; Chanley, Charles; 1. Lee, Hyunkoo; Park, Insun; Kwak, Dodd, Sonia R.; Roush, Jared; Jeonghun; Yoon, Do Y.; Kallmann, Schmidt, John; Srdanov, Gordana; Changhee Lee (2010). "Improvement Stevenson, Matthew; Wessel, Ralf; of electron injection in inverted Innocenzo, Jeffrey; Yu, Gang; bottom-emission blue phosphorescent O'Regan, Marie B.; MacDonald, W. organic light emitting diodes using A.; Eveson, R.; Long, Ke; Gleskova, zinc oxide nanoparticles". Applied Helena; Wagner, Sigurd; Sturm, James Physics Letters. C. (2003). "Active-matrix OLED using 2. Kim, Yang Wan; Kwak, Won Kyu; 150°C a-Si TFT backplane built on Lee, Jae Yong; Choi, Wong Sik; Lee, flexible plastic substrate (Proceedings Ki Yong; Kim, Sung Chul; Yoo, Paper)". SPIE Proceedings. EuiJin (2009). "40 Inch FHD AM- 8. Seth Coe; Wing-Keung Woo; Moungi OLED Display with IR Drop Bawendi; Vladimir Bulovic (2002). Compensation Pixel Circuit". SID "Electroluminescence from single Symposium Digest of Technical monolayers of nanocrystals in Papers. molecular organic devices". 3. Lee, Myung Ho; Seop, Song Myoung; Kim, Jong Soo; Hwang, Jung Ho; Shin, HyeJin; Cho, Sang Kyun; Min, Kyoung Wook; Kwak, Won Kyu; Dr. Vandana Khare is working as Jung, Sun I; Kim, Chang Soo; Choi, Professor in CMR College of Engineering Woong Sik; Kim, Sung Cheol; Yoo, & Technology in ECE department. She Eu Jin (2009). "Development of 31- completed her PhD in Communication Inch Full-HD AMOLED TV Using Engineering from JNTU Hyderabad (T.S), LTPS-TFT and RGB FMM". SID M.E (Digital techniques) in 1999 from SGSITS, INDORE (M.P) India and B.E in

Journal of Radio and Television Broadcast Volume 3 Issue 3

ECE in the year 1994 from GEC Rewa (M.P). She has 20 years of teaching experience. She has published 27 research N. K. Shreyas is pursuing his papers in International journals B.tech in Electronic & Communication &presented 05 papers in National & Engineering in CMR College of International conferences. She is life Engineering & Technology, Hyderabad. member of ISTE & IETE Technical His research Interests’ include Microwave societies. Her research Interest includes and RADAR remote sensing systems, computer networks, mobile computing and Display systems, Micro-electronics and Bio-medical imaging. Digital Forensics.