Indoor lighting in homes and offices and public outdoor lighting account for approximately 20% of all electricity consumption in developed countries. An EU initiative developed efficient light-emitting diodes (LEDs) to address the issue. LEDs are gradually replacing fluorescent tubes in solid-state lighting solutions. They convert electric current directly into light and have very long operating lifetimes.
Today's LED-based solid-state lighting relies on a combination of violet LEDs with phosphors emitting in the yellow and red part of the spectrum to produce white light.
With this in mind, the EU-funded NWS4LIGHT (Nanowires for solid state lighting) project set out to develop improved LEDs for four key light wavelengths in the visible spectrum: blue, green, yellow and red.
Several nanowire structures for LED applications were developed, namely conventional and core-shell nanowire (NW) LED (NW-LED) structures based on indium gallium nitride, and aluminium gallium indium phosphide materials systems already used for commercially available planar LEDs.
Project partners began by characterising related physical properties using novel experimental methods, namely optical, electron microscopy and rapid analytical techniques. This led to new developments, such as mapping and measuring single NW-LED structure profiles. A production facility was set up to test the developed NW-LEDs.
For the growth of nanowires, researchers demonstrated that a chemical process used to produce high quality, high-performance solid materials is ideal for developing core-shell NW-LED structures in a very precise manner.
The NWS4LIGHT team demonstrated a device processing technology for the NW-LEDs by using a wafer process flow that operates on a commercial wafer fabrication line. To do so, it compared the predicted performance of NW-LEDs with lumen and colour maintenance, wall-plug efficiency, reliability and projected production cost.
Team members successfully illustrated that NW-LEDs can be produced using such technology which allows them to be integrated into systems with several devices.
NWS4LIGHT's NW-LEDs eliminate the use of hazardous materials and increase lifetime and efficiency through elimination of phosphor. The polychromatic NW-LEDs also provide greater opportunity for tailoring light depending on need. The improved low-cost solution is expected to tap into a large commercial market with important benefits for producers and the EU economy.