Organic LEDs. Yuhan Ye Apr. 26

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1 Organic LEDs Yuhan Ye Apr. 26 Special topic presentation for C150 4/26/2018 1

2 Outline Brief introduction and advantages of OLED Working principles Examples for different kinds of OLEDs and processing methods Commercial uses and applications Problems and weakness Special topic presentation for C150 4/26/2018 2

3 Brief introduction OLED = Light Emitting Diode + Organic emissive electroluminescent layer Similar working principles with LED (recombination of holes and electrons leads to emission of light) Main categories: small molecular and ploymer Application : portable and large-area flat panel displays; lighting Special topic presentation for C150 4/26/2018 3

benefits: ease of fabrication flexible and transparent low

4 Advantages-why we choose OLED 1,2,3 thin, lightweight better power efficiency better picture quality polymer benefits: ease of fabrication flexible and transparent low cost of materials Special topic presentation for C150 4/26/2018 4

5 Working principles 4 organic conductive materials: delocalization of pi electrons conjugation conductivity levels ranges from insulators to conductors(we consider organic semiconductors for OLED) HOMO -> valence band LOMO -> conduction band Special topic presentation for C150 4/26/2018 5

6 Working principles structures 5 OLED LED Special topic presentation for C150 4/26/2018 6

7 Working principles processes 5 Injection(electron to cathode LUMO, hole to anode HOMO) Transport(blocking layer) Recombination(efficiency-> electron and hole density) Migration and decay Special topic presentation for C150 4/26/2018 7

8 Examples (TOLED) transparent contacts on both sides of OLED make Head-up display(military aviation) Special topic presentation for C150 4/26/2018 8

vertically stacked geometry higher resolution; more

9 Examples(stacked OLED 6 ) require organic thin films are transparent R,G,B emission layers are placed in vertically stacked geometry higher resolution; more luminous Special topic presentation for C150 4/26/2018 9

Examples(dendrimer OLED 7 ) white LED => mixture of multichromophores energy transfer between different dyes contamination of origin emission color generation; site

10 Examples(dendrimer OLED 7 ) white LED => mixture of multichromophores energy transfer between different dyes contamination of origin emission color generation; site isolation; prevent energy transfer between cores(dyes) only need to tune the blending ratio of each component dendrimer Special topic presentation for C150 4/26/

11 Applications smartphone screen 8 ; TV screen - > compared to LCD flexible full color OLED display flexible OLED lighting Special topic presentation for C150 4/26/

12 Problems & Challenges lifespan(lower than typical lifetime of LCD,LED) color balance(blue light decrease faster than red, green) water damage power consumption Special topic presentation for C150 4/26/

13 Citing 1 Sekitani, T.; Nakajima, H.; Maeda, H.; Fukushima, T.; Aida, T.; Hata, K.; Someya, T. Stretchable Active-Matrix Organic Light-Emitting Diode Display Using Printable Elastic Conductors. Nature Materials 2009, 8, G.Gustafsson, Y. C., G. M. Treacy, F. Klavetter, N. Colaneri & A. J. Heeger, Flexible light-emitting diodes made from soluble conducting polymers Nature 1992, 357, Dirk Ammermann, A. B., Wolfgang Kowalsky, Multilayer Organic Light Emitting Diodes for Flat Panel Displays. Annual report 1995, Institut für Hochfrequenztechnik, TU Braunschweig 1995, Walzer, K.; Maennig, B.; Pfeiffer, M.; Leo, K. Highly Efficient Organic Devices Based On Electrically Doped Transport Layers. ChemInform 2007, Bardsley, J. N., International OLED Technology Roadmap. IEEE Journal of Selected Topics in Quantum Electronics 2004, 10 (1), Forrest, S.; Burrows, P.; Shen, Z.; Gu, G.; Bulovic, V.; Thompson, M. The Stacked OLED (SOLED): A New Type Of Organic Device For Achieving High-Resolution Full-Color Displays. Synthetic Metals 1997, 91, Li, J.; Liu, D. Dendrimers For Organic Light-Emitting Diodes. Journal of Materials Chemistry 2009, 19, OLED vs LCD: How the iphone X s display changes everything. (accessed Sep 22, 2017) Special topic presentation for C150 4/26/

14 Questions Special topic presentation for C150 4/26/

Performance Comparison of Bilayer and Multilayer OLED

Performance Comparison of Bilayer and Multilayer OLED Akanksha Uniyal, Poornima Mittal * Department of Electronics and Communication School of Engineering and Technology Graphic Era University, Dehradun-248002,