APPLICATION OF THIN FILMS

ANEETTA DAVISMSc NS & T, 2nd SEMMOUNT CARMEL COLLEGE

WHAT IS THIN FILM?

• thin = less than about one micron ( 10,000 Angstroms, 1000 nm)

• film = layer of material on a substrate

The need for thin films is because we can alter their properties and for miniature devices.

APPLICATIONS

• SOLAR CELLS• THIN FILM TRANSISTORS• OPTICAL COATING• THIN FILM BATTERIES

SOLAR CELLS• This is a cheaper raw material than crystalline silicon. No

structural damage!• The conversion of solar light to electric power is one of the

available renewable sources of energies.• The basic physical principle involved is the absorption of

photon resulting in the creation of electron-hole pairs; the excess electrons in the conduction band, and holes in the valence band.

• Depositing one or several thin layers of photovoltaic material onto a substrate is the basic gist of how thin-film solar cells are manufactured.

ADVANTAGES OF THIN FILM SOLAR CELLS

• Mass-production is simple and potentially cheaper to manufacture than crystalline-based solar cells.

• Can be made flexible, which opens up many new potential applications.

• High temperatures and shading have less impact on solar panel performance.

• In situations where space is not an issue, thin-film solar panels can make sense.

DISADVANTAGES OF THIN FILM SOLAR CELLS

• Thin-film solar panels are in general not very useful for in most residential situations. They are cheap, but they also require a lot of space.

• Thin-film solar panels tend to degrade faster than mono- and polycrystalline solar panels, which is why they typically come with a shorter warranty

THIN FILM SOLAR PANELS

THIN FILM TRANSISTORS

• TFT is made by depositing thin films on semiconductor.

• A common substrate is glass since the primary application of TFT’s are Liquid Crystal Displays.

What is TFT LCD ?

• TFT LCD is a sandwich like structure with crystal filled between two glass plates.

• It is common in notebook computers , that it has transistor for each pixel.

How do they work ?

• TFT glass has as many TFTs as the number of pixels displayed.

• Millions of pixels create an image on the display.• TFT’s act as switches to individually turn ‘on’ and ‘off’

for each pixel• A color filter glass has color filter which generates color.• Diffuser distributing the light evenly near the viewing

area.• Liquid Glass Crystals move according to the change in

voltage between the TFT glass and color filter.

ADVANTAGES

• Light weight• Portable • Low power

consumption• High resolution• Wide variety of

commercial application

DISADVANTGES

• The general comment from the people is that the LCD TFT gets switched off after sometime .

• The liquid crystals inside the display are poisonous

• Spills off from a cracked display should be washed with soap water.

OPTICAL COATING

An optical coating is one or more thin layers of material deposited on an optical component such as a lens or mirror, which alters the way in which the optic reflects and transmits light.

ANTIREFELCTION COATING

• Whenever light travels between two interfaces of different refractive index, some of the light is reflected.

• These reflections form flare images.• The coating of optical surfaces with antireflection

coatings has resolved this problem.• The antireflection coatings should be applied to

optical surfaces containing germanium, silicon or materials with high refractive index.

Antireflection coating

THIN FILM BATTERIES

• Unlike typical batteries, thin film batteries are all solid-state.

• In many cases they can be made flexible. • They can be manufactured using normal thin

film deposition techniques.

HOW DO THEY WORK?Thin film lithium ion batteries are widely used in the industry. It

consists of:• Cathode materials: Cathode materials in thin film lithium ion

batteries are the same of what is seen in classical lithium ion batteries. They are normally metal oxides that are deposited as a film by various methods like pulsed laser deposition, magnetron sputtering, CVD, Sol-gel processing.

• Electrolyte: The greatest difference between classical lithium ion batteries and thin, flexible, lithium ion batteries is in the electrolyte material used. The electrolyte plays a major role in safe battery operation. LiPON, lithium phosphorus oxynitride, is an amorphous glassy material used as an electrolyte material in thin film flexible batteries. Layers of LiPON are deposited over the cathode material at ambient temperatures by RF magnetron sputtering. This forms the solid electrolyte used for ion conduction between anode and cathode.

•SEPARATOR MATERIAL: Here the electrolyte is a solid, which conveniently satisfies both the ion transportation and the physical separation requirements without the need for a dedicated separator.

•CURRENT COLLECTOR: Current collectors in thin film batteries must be flexible, have high surface area, and be cost-effective.

ADVANTAGES

• Higher average output voltage• Lighter weights• Longer cycling life• Low maintenance

OTHER APPLICATIONS

• Semiconductors• Super capacitors• Data storage• Photo electrochemical cells• Drug delivery• Nanomedicine

REFERENCES

• http://www.worldscientific.com/doi/pdf/10.1142/S2010194513010696

• http://shodhganga.inflibnet.ac.in/bitstream/10603/4025/8/08_chapter%202.pdf

THANK YOU