Silole Derivative Properties in Organic Light Emitting Diodes

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1 Silole Derivative Properties in Organic Light Emitting Diodes E. Duncan MLK HS Physics Teacher Mentors: Prof. Bernard Kippelen & Dr. Benoit Domercq

2 Introduction Theory Methodology Results Conclusion Acknowledgements References Outline

3 Introduction Objective Definitions What is an OLED? What is a Silole? Motivation

4 Objective Organic light emitting diodes (OLED( OLED) ) were fabricated using a new family of materials based on silole derivatives. 4 Si Si Si XZ-I-151 XZ-II-69 XZ-I-125 Si Ph H XZ-I-149B

5 What is an OLED? OLEDs,, organic light emitting diodes, are solid-state state devices composed of thin films of organic molecules that create light with the application of electricity. 1 They are practically the dynamic opposite of Solar Cells, which create electricity with the application of light.

6 What is a Silole? Siloles are a family of materials that have been found to have high external quantum efficiencies and electron transport properties. 4

Motivation http://www.universaldisplay.com/foled.htm http://www.engadget.

multilayer devices that do not require a backlight Printed on plastic making displays flexible and

7 Motivation Provide brighter, crisper displays on electronic devices Very thin multilayer devices that do not require a backlight Printed on plastic making displays flexible and lightweight Use less power than conventional LEDs or liquid crystal displays (LCDs) Much less costly to fabricate than traditional LCD displays

8 Theory Basic OLED Structure How an OLED works

9 Basic OLED Structure Multilayer device made up of Anode Organic Layers Cathode Organic Layers consist of Hole Transport Layer (HTL) Electron Transport Layer (ETL) Emissive Layer (EL) Anode HTL ETL Cathode Light

Basic OLED Structure (cont d) Substrate Anode Organic Layers Conducting Layers HTL ETL Emissive Layer (EL) Cathode http://science.howstuffworks.

10 Basic OLED Structure (cont d) Substrate Anode Organic Layers Conducting Layers HTL ETL Emissive Layer (EL) Cathode Substrate - The substrate is made of glass and supports the OLED. Anode - The anode removes electrons (adds electron "holes") when a current flows through the device. Conducting Layer(s) - One layer made of organic plastic molecules that transport "holes" from the anode. (HTL)) Another layer made of organic plastic molecules (different from those in hole transport layer) that transport electrons from the cathode. (ETL( ETL) Emissive Layer This organic layer is where light is made. (EL) Cathode - The cathode injects electrons when a current flows through the device. d

11 How an OLED works Holes are injected from the anode and recombine with electrons injected from the cathode creating an exciton which emits light when it relaxes to the ground state. hν HTL e- Emission Layer Exciton e- ETL Anode e- Cathode Electron Injection Anode Hole Injection

12 An OLED device made out of the silole material presented in this study. Anode Cathodes (5 devices)

13 Methodology Experimental Apparatus Device Fabrication Materials Used OLED Measurements

14 Experimental Apparatus Physical Vapor Deposition System Double-Glove Box System

15 Physical Vapor Deposition system with 4 low power sources to deposit organic materials and 2 high power sources to deposit metals

16 A Double-Glove Box System with a integrated spin-coater to fabricate thin films from solution

17 Device Fabrication Nitrogen environment Layers are deposited using spin-coating techniques The material is sublimated and deposits evenly onto the substrate

18 Materials Used Anode: indium tin oxide (ITO) 150 nm Organic layers: HTL:a copolymer based on N- N -diphenyl-n-n bis(3- methylphenyl)-[1 [1-1 -biphenyl] biphenyl] diamine (TPD)) 40 nm ETL: tris-(8 (8-hydroxyquinoline) aluminum (AlQ( 3 ) 40 nm EL: siloles derivatives blended with polystyrene (4:1 weight ratio) 40 nm Cathode: Lithium Fluoride (LiF( LiF) ) 1 nm and Aluminum 300 nm N TPD N O O Al O N N N AlQ 3

19 OLED Measurements Voltage is applied to the device Record current flowing through the device Forward light output data is collected Electroluminescent spectrum is taken From this data, analysis can be done on the device performance

20 Results OLED Analysis Spectrum of OLEDs with silole derivatives in Polystyrene (4:1 wt-%) L, J, V characteristics as EL L, J, V characteristics as ETL Findings & Expectations

21 OLED Analysis Current Density - amount of current flowing per unit area (ma/cm 2 ) Luminescence - accounts the photopic response of the eye, the sensitivity response of the photodetector and the physical geometry of the measurement set-up (cd/m 2 ) External Quantum Efficiency - the measurement of the number of photons emitted from the device in the forward direction divided by the number of electrons injected into the device (%)

22 Spectrum of OLEDs with silole derivatives in Polystyrene (4:1 wt-%) Emission layer configuration (EL) Al (200 nm) LiF (1 nm) Alq 3 (40 nm) Silole:PS (40 nm) Poly-TPD-MeO 2 (35 nm) ITO Glass EL spectrum of Silole derivatives Electron transport layer configuration (ETL) EL spectrum of Silole derivatives Al (200 nm) LiF (1 nm) Silole:PS (40 nm) Poly-TPD-MeO 2 (35 nm) ITO Glass AH-IV-7 Electroluminescence (a.u.) 1.0 XZ-III-28 XZ-VI-96 XZ-I XZ-I-149d XZ-I Alq Wavelength (nm) public\shared\oled\siloles\ah-iv-7\spectrum AH-IV-14 Electroluminescence (a.u.) XZ-III XZ-VI-96 XZ-I-151 XZ-I-149d 0.0 XZ-I Wavelength (nm) public\shared\oled\siloles\ah-iv-7\spectrum

23 L, J, V characteristics as EL Current Density (ma/cm 2 ) AH-IV-7 J-V characteristics of different siloles as EL E-3 1E-4 1E-5 1E-6 XZ-III-28 XZ-VI-96 XZ-I-151 XZ-I-149d XZ-I-125 1E-7 1E Applied Voltage (V) public\shared\oled\siloles\ah-iv-7\ah-iv-7 AH-IV-7 L-V & EQE-V characteristics of different siloles as EL Luminance (cd/m 2 ) E Applied Voltage (V) XZ-III-28 XZ-VI-96 XZ-I-151 XZ-I-149d XZ-I Ext. Quantum Efficiency (%) public\shared\oled\siloles\ah-iv-7\ah-iv-7

24 L, J, V characteristics as ETL Current Density (ma/cm 2 ) AH-IV-14 J-V characteristics of different siloles as ETL E-3 1E-4 1E-5 1E-6 XZ-III-28 XZ-VI-96 XZ-I-151 XZ-I-149b XZ-I-125 1E-7 1E Applied Voltage (V) public\shared\oled\siloles\ah-iv-14\ah-iv-14 L-V & EQE-V characteristics of different siloles as ETL Luminance (cd/m 2 ) AH-IV E Applied Voltage (V) XZ-III-28 XZ-VI-96 XZ-I-151 XZ-I-149b XZ-I Ext. Quantum Efficiency (%) public\shared\oled\siloles\ah-iv-14\ah-iv-14

25 Findings & Expectations Current density, luminance, and external quantum efficiency were observed. Although the emission layer configuration (EL) efficiency was minutely greater than that of the electron transport layer configuration (ETL), the results were essentially the same for both. The efficiency was between 1 and 3% for both configurations.

26 Conclusion Found that OLED testing is very rigorous & detailed work Not easy to find high efficiency (> 3%) Higher efficiency with blue light emission is important future goal Good results in future very possible since this research team is dedicated, diligent, persistent, and supportive of one another

27 Acknowledgements Prof. Bernard Kippelen,, Professor Dr. Benoit Domercq,, Research Scientist Andreas Haldi,, Graduate Research Assistant The Remainder of the Kippelen Research Group of the Georgia Tech School of Electrical and Computer Engineering

28 The Kippelen Research Group

29 Acknowledgements (cont d) Doctors Edward and Leyla Conrad, Step-Up Georgia Institute of Technology National Science Foundation

30 References , 1-Diphenyl1 Diphenyl-2,3,4,5-tetrakis(9,9-dimethylfluoren- 2-yl)silole Properties in Organic Light-Emitting Diodes and Organic-Field Effect Transistors,Sarah Montgomery, Purdue University, Bernard Kippelen, Benoit Domercq School of Electrical & Computer Engineering, Georgia Tech, Chen, H. Y.; et al. Appl.. Phys. Lett , 81, (4),

Fundamentals of Organic Light Emitting Diode

Fundamentals of Organic Light Emitting Diode M. F. Rahman* 1 and M. Moniruzzaman 2 Organic light emitting diode (OLED) has drawn tremendous attention in optoelectronic industry over the last few years.