Post on 12-Feb-2017
ORGANIC THIN FILM TRANSISTORS
Chemical Processes For Display Devices Professor Heeyeop Chae
Presented by Hussain FiazStudent ID 2016711218
Outline1. Motivation and introduction2. Types and mechanism3. Different advancement4. Vacuum and solution based processes5. Applications
What and why an organic transistor?• First Organic Transistor - 1986
• Using organic molecules (Polymers) rather than silicon for their active material.
• Semiconductor• Advantages
1. Light weight, 2. flexible, 3. Cheap4. Solution Processing Photolithographic patterning5. lower temperature manufacturing (60-120° C) 6. Print-able Organic Transistors7. compatibility with plastic substances 8. foldable & light weight
(Tsumura et al. 1986.B. kumar et al. 2014.
Device Structure
• Important parameters Key Parameters
– Mobility (µ ≈ 1-10 cm2/vs)
– On-Off Ratio• Suitable (106)
– Threshold voltage
– Colin Rees et al. 2005
Device design• Top contact • Bottom contact
Top contact devices have superior performance sue to low contact resistance between the source and active layer.
Roichman et al. 2004
Comparison of different OTFTs
Comparative plot of the OTFTs which are based on different materials is shown.
Different materials have been assed to improve the device performance.Among all the materials pentacene based organic thin film transistors or electronic devices have best field effect mobility.
Feng et al. 2015, B. kumar et al 2014
Interlayer between electrode and insulator
Capacitance and leakage current of the device is reduced.
J. Yoon et al. 2013 C. Chu et al.2005
High Performance OTFT with a metal/metal oxide bilayer electrode
• TMO helps in controlling work function and charge injection properties
• Reduces contact barrier and prevents the diffusion
*Chih-Wei Chu, Sheng-Han Li, Chieh-Wei Chen, Vishal Shrotriya, and Yang Yang, High-performance organic thin-film transistors with metal oxide/metal bilayer electrode, Applied Physics Letters 87, 193508 (2005);
Other key factors to improve Field Effect Mobility • Higher the dielectric constant of insulator higher will be the field effect mobility
• k↑ → Polarization↑ → Carrier Density↑ → Mobility↑
• Dielectric roughness also effect the field effect mobility
• Roughness↓ → Mobility↑
• Higher the contact resistance of the insulator with the electrodes will lower the field effect mobility. Penetration of the electrode into the dielectric also effect the mobility, higher the penetration lower will be the mobility
• Au coated (PEDOT/PSS) Charge Injection↑ → Contact Resistance↓ → mobility↑
• H. H. Lee et al. Appl. Phys. Lett. (2005)• 18- R. Schroeder et al, Appl. Phys. Letts (2005)
Vacuum Processes Solution Processes
PECVD , PVD, LPCV, OVPD
Conventional ProcessProvides advantage of Deposition Rate MonitoringControlledCostly
Colin et al. 2011.
Coating by Spray, spinElectrodepositionElectroless depositionAlso includes printing processes
Very lost CostFlexibleCan be used for large area applicationsEfficiency few orders
FlexibleOLED
FlexibleLCD
OrganicMemory
ImageSensor
BioSensor
OrganicLaser
Smart CardRFID Tag
E-paper
OTFT
ICTechnology
OpticalTechnology
BioTechnologyApparel
Technology
SensorTechnology
Memory device
Technology
LCDTechnology
OLEDTechnology
E-PaperTechnology
Smart Textile
Application of Organic TFT
Any Question?