Development of nonvolatile white light-emitting liquid that is coatable on diverse range of materials

May 30, 2012
Fig: (a) Preparation of white light-emitting paste material by mixing solid dyes of green color (Alq3) and orange (rubrene) in a room temperature OPV iquid. (b) White light-emission of characters written with a ballpoint pen (365nm UV irradiation). (c) Large area coating emits white light on area of 5 x 5 cm2 (365nm UV irradiation). (d) 375nm UV-LED light-emitting photograph. (Left) Without coating with white light-emitting paste and (right) with coating.

A Japanese research team headed by Dr. Takashi Nakanishi of the National Institute for Materials Science developed a nonvolatile liquid material which emits white light at room temperature.

Because account for about 20% of all electric power consumption, and technological improvements are desired in order to reduce emissions of (GHG). In particular, high expectations are placed on organic materials which emit white light as a material for next-generation lighting, replacing today’s incandescent light bulbs and fluorescent tubes. Although the organic materials which have been developed to date display a white light-emitting property when dispersed in a solution, the molecules tend to aggregate when the solution is coated on a substrate and the solvent is evaporated. This problem is the reason why these materials cannot fully demonstrate their intrinsic white-light emitting performance. Furthermore, from the viewpoint of the manufacturing process, an which can be prepared by a simple method, without use of volatile organic solvents, achieving high brightness, homogeneous white light-emission, had been desired.

Dr. Nakanishi’s team developed a liquid material with blue light fluorescence which is nonvolatile, has a melting point of approximately -45°C, and solves the problem of molecule aggregation, by modifing highly flexible branched alkyl chains around the molecule that can emit fluorescence. This material is a liquid with a viscosity of approximately 1.0 Pa·s, which is similar to that of lubricating oil, and does not require use of a volatile organic solvent. It displays blue light emission with an absolute fluorescent quantum yield of approximately 50%. A white light-emitting paste material can also be prepared by mixing a small amount of luminescent dyes in solid powder in the liquid. Various materials which emit high brightness white light even when coated were successfully prepared, including printing of white light-emitting characters, large area coating, white light-emitting lights by coating on a UV-LED surface, and others.

This research achieved the development of materials which emit white light with high quality using only an extremely simple operation, namely, mixing of a small amount of solid dyes in the nonvolatile, blue light-emitting liquid. This liquid material can be coated on substrate surfaces with various shapes, and thus is expected to enable broad simplification of the manufacturing processes for lighting devices and other products. Because the emitted color can be controlled with a high brightness, and liquids that display full-color light emission can also be prepared easily, this material is expected to become a new light-emitting material for next-generation printable electronics.

Explore further: New CMI process recycles magnets from factory floor

More information: These research results were published in Angewandte Chemie International Edition (2012, 51, 3391-33), which is a publication of the German Chemical Society, and were also highlighted in Nature (2012, 484, 9).

Related Stories

Berkeley Researchers Light Up White OLEDs

Apr 06, 2010

(PhysOrg.com) -- Light-emitting diodes, which employ semiconductors to produce artificial light, could reduce electricity consumption and lighten the impact of greenhouse gas emissions. However, moving this ...

Building a better light bulb

Feb 01, 2012

Scientists study the movement of charge carriers to design an organic LED that is energy efficient and still casts a warm, natural glow.

High-brightness breakthrough

Jun 28, 2005

As a result of cooperation between Philips Lighting, Philips Research and Novaled have announced a new record for the efficiency of high-brightness white OLEDs, a new solid state lighting technology. OLEDs are expected to ...

Highly efficient organic light-emitting diodes

Aug 09, 2011

(PhysOrg.com) -- Organic light-emitting diodes (OLEDs) are seen as a promising replacement for the liquid-crystal displays (LCDs) used in many flat-screen televisions because they are cheaper to mass-produce. ...

Recommended for you

New CMI process recycles magnets from factory floor

2 hours ago

A new recycling method developed by scientists at the Critical Materials Institute, a U.S. Department of Energy Innovation Hub led by the Ames Laboratory, recovers valuable rare-earth magnetic material from ...

Chemists characterize 3-D macroporous hydrogels

5 hours ago

Carnegie Mellon University chemists have developed two novel methods to characterize 3-dimensional macroporous hydrogels—materials that hold great promise for developing "smart" responsive materials that ...

Substrates change nanoparticle reactivity

11 hours ago

(Phys.org)—Nanoscale materials tend to behave differently than their bulk counterparts. While there are many theories as to why this happens, technological advances in scanning tunneling microscopy (STM) ...

Reviving cottonseed meals adhesives potential

14 hours ago

Cottonseed meal—the leftovers after lint and oil are extracted from cottonseed—is typically fed to ruminant livestock, such as cows, or used as fertilizer. But Agricultural Research Service scientists ...

New concrete composite can heal itself

14 hours ago

In the human body, small wounds are easily treated by the body itself, requiring no further care. For bigger wounds to be healed, the body may need outside assistance. Concrete is like a living body, in that ...

Actuators that mimic ice plants

14 hours ago

Engineers developing moveable robot components may soon take advantage of a trick plants use. Researchers at the Max Planck Institute of Colloids and Interfaces in Potsdam and Harvard University in Cambridge ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.