Guided by Miss. Shahida

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 gateb)Top gate

Possible structure, (a) Bottom gate, and (b) Top gate.

Operation of a bottom gate TFT

Strengths and WeaknessesStrengths WeaknessesVisible 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