'Thin films & coatings' Roadmap - Nano Mahidol

Organic Light-Emitting Diode (OLED): An OLED is made of semiconducting organic
polymers. Varying amounts of OLEDs can be deposited in arrays on a screen using
printing methods (section 2.3.3) to create a graphical colour display or lighting
devices. OLEDs are available as distributed sources while the inorganic LEDs are
point sources of light. Main advantage of OLED displays is that OLED displays don't
require a backlight to function: they consume far less power and could be used in
portable devices. The possibility to produce displays (or solar cells) as a continuous
sheet rather than one panel at a time could also have a very positive impact on
production costs.
Besides the use of OLEDs as displays, there’s significant research looking at their
exploitation as solid-state light sources. There are several running projects building
first prototypes. Most suitable materials include a.o. polyfluorene, PPV, PEDOT or
Ca or Ba thin films.
Solar cells
Current thin-film solar cell technologies are limited by either the ultimate efficiency
that can be achieved with the device material and structure or the requirement for
high-temperature deposition processes that are incompatible with all presently known
flexible polymer substrate materials. Nanotechnology could address both limitations
by:
• The development of deposition processes exploiting advantages of (expensive)
mono or polycrystalline silicon (e.g. higher electron mobility). For instance, the
combination of thin films of a-Si and c-Si is close to commercialisation.
• TiO 2 thin films could improve photovoltaic cells efficiency over glass substrates.
• The development of low temperature processes for the deposition of thin film
semiconductor materials (e.g. ZnO, CdS, CuInSe 2 ) for photovoltaic cells on
lightweight flexible plastic substrates.
• On the long term, replacing Indium TinOxid (ITO) transparent electrodes by
conducting polymers (i.e. PEDOT or polyaniline) offering increased electrical and
thermal properties as well as processability.
Magnetic RAM (Non-Volatile Memory)
Thin films have attracted great attention in recent years for their potential use in
Dynamic RAMs and Multi Chip Modules (MCM) due to their high dielectric constant
and relatively low leakage current. In D-RAM, each storage cell consists of a
transistor and a capacitator, the last discharging quickly and having the need to be
re-charged. M-RAM is built up of units called magnetic tunnel junctions that consist of
2 thin-film metal layers separated by an insulator. A tunnel junction stores a single bit
of data and to write data you would only need to change its spin by applying a
magnetic field. Main advantage is that there isn’t the need to constantly supply
electric power to maintain the data (thousands of time per second in nowadays RAM)
avoiding data loss and drastically reducing power consumption.
Planar waveguides and other optical components
The optics’ industry has been using thin film coatings in components like lenses,
prisms, filters, reflectors or mirrors. Developments have mostly been pushed by the
high demand to increase bandwidth in optical fibre networks by breaking the laser
33 Roadmap report on
Thin films and coatings