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Transparent
ElectronicsSubmitted by, Sajas K.K. Roll no: 18 S5 EC
Introduction
What is transparent electronics?
In transparent electronics the usual
opaque semiconductor materials forming the
basis for electronic device fabrication is
replaced with transparent materials.
There are two technologies which
preceded and underlie transparent
electronics:
1. Transparent Conducting Oxides (TCOs)
2. Thin Film Transistors (TFTs)
Transparent Conducting Oxides TCOs)
TCOs constitute an unusual class of
materials possessing two physical properties
(generally considered mutually exclusive):
1. High optical transparency. ( Eg>3.1eV)
2. High electrical conductivity.
Transparent electronic devices
Transparent Passive devices
Transparent Active devices
Transparent Passive devices
Transparent Thin Film Resistors
Transparent Thin Film Capacitors
Transparent Thin Film Inductors
Transparent Thin Film Resistors
Resistive material: ITO (Indium Tin Oxide)
Typical sheet resistance ~ 10-
Conductivity of TCO’s depends on number of oxygen vacancies ( and metal atoms occupying interstitial sites.
Transparent Thin Film Capacitors
Most insulators are transparent.
Contact layer is made of highly conducting TCOs (ITO).
Transparent Thin Film Inductors
Hard to realize due to poor conductivity of TCO’s compared to metals.
High L requires larger number of turns which in turn results in increased parasitic resistance.
Schottky Barriers
Formed from metal (anode)-semiconductor (cathode) junction.
Space charge region (depletion region) and potential barrier formation due to difference in work function of metal and semiconductor.
Schottky barrier height
, where Schottky barrier height
work function of metal
Electron affinity of semiconductor
Energy band in a Schottky barrier
Transparent Thin Film TransistorsConstitutes the heart of transparent
electronics
Channel is formed from highly insulating, wide band gap transparent semiconductor(ZnO).
Source, drain and gate contacts are made from highly conductive TCO (ITO).
Two possible configurations are:a)Bottom gate
b)Top gate
Possible structure, (a) Bottom gate, and (b) Top gate.
Operation of a bottom gate TFT
Strengths and WeaknessesStrengths Weaknesses
Visible transparency High resistance of TCO’s
Large area Lack of complementary devices
Low cost (solution based deposition and printing)
Low frequency of operation.(KHz to few MHz).fT=
Low temperature processing Technological immaturity
Free real estate
Passive availability (R & C)
Robust stable inorganic materials
Safe, nontoxic materials
Applications
Active Matrix LCD (AMLCD).
Active Matrix Organic Light Emitting Device display backplane (AMOLED).
Value added glass.
Transparent electronics on opaque substrates.
UV detectors and arrays
• Transparent solar cells
• UV detectors for spectrally resolved imaging.
• Security applications:
Invisible cameras and
Invisible RFID’s
Conclusion
• Started as a mere electrical device
technology during world war 2,
transparent electronics now holds the key
for many future advancements in security,
entertainment efficient utilization of
energy.
Reference• ‘Transparent Electronics ’, Springer
publications, J.F.Wager, D. A. Keszler, R. E. Presley.
• ‘Transparent electronics: from synthesis to applications’, Wiley publications: Antonio Facchetti, Tobin J. Marks
Thank you