Categories Lighting

Better Materials for OLED Lighting

LEDs have been replacing traditional lighting at a rapid pace, offering longer life times, more efficiency, lower cost, etc. OLED lighting promises to complement LED lighting by offering better color performance, power efficiency, unique shapes and designs, as well as a thin, lower weight and elegant profile. To enable OLED technology in this emerging lighting market, there is a need to replace traditional materials with new, better-performing materials such as silver nanowires.


Figure 1. Image of Silver Nanowires at 70° tilt

Silver Nanowires
In an OLED device, the top electrode is made of a transparent conductor and plays an important role in light transmission/efficiency. A transparent conductor made of silver nanowires allows for high conductivity with excellent transmission and acts as the top electrode/anode in the case of an OLED lighting system. Silver nanowires in the top electrode are used in the form of a network of wires (see Figure 1) that are a few nanometers thick and a few micrometers in length. With silver being the best conductor on the planet, the network of overlapping nanowires offers conductivity less than 10 ohms/sq while allowing 94 percent of the light to go through the percolated network.


Figure 2. High transmission of silver nanowires at low resistance (Photo courtesy – ClearOhm silver nanowire material by Cambrios Technologies)

Aesthetic Lighting
OLED lighting is not a point source and, therefore, does not need to be diffused or set at a distance from the area that needs to be lit. OLEDs emit light all through their surface and can be used to create aesthetically pleasing lighting structures of various forms and sizes. Imagine an elegantly shaped lampshade emitting light instead of the shade diffusing the light from the lamp within. Lights in any form factor that needs to be bent, curved or flexed, needs flexible transparent conductors. This can be achieved easily through the use of silver nanowires rather than thick and brittle conductors.


Figure 3. OLED lighting tiles. Photo courtesy – Panasonic

OLED devices can serve a dual purpose of being a window or a light. They can be made transparent – a window that you can see thru during the day and that would emit light at night. The skylights and car sunroof could not only allow ambient light to enter, also could become lamps at night. In such applications, it is important to have very transparent layers of OLED materials, another area where silver nanowire networks play a huge role.

In addition, OLED lighting can offer shades of color previously not possible with conventional lighting. Better color tuning is possible with silver nanowires, and OLED lights can offer a more precise shade of color for premium lighting applications.

2.5D Lighting
OLED lights can be produced on plastic substrates and coated with silver nanowires. These types of flexible and rugged form factors can be deployed on non-flat surfaces, such as the dashboard of a car. This type of 2D and 2.5D lighting systems are very desirable in high-end consumer devices, retail stores and museums where any surface can provide changeable color. The traditional transparent conductor materials like ITO (indium tin oxide) are brittle and don’t lend themselves to bending or shaping, hence newer materials such as silver nanowires, which are malleable and ductile, are preferred.

Thinner, Lightweight, Rugged
Silver nanowires complement OLED in that both materials are thin, lightweight and very rugged. The thin and lightweight features make them suitable for applications such as aircraft lighting and illuminating skyscrapers, and the rugged nature of the system (both OLED and silver nanowires can be coated on plastic or thin glass) makes them suitable for outdoor public venues, which typically require lighting that is not only bright but also unbreakable.

LED and OLED technologies will reshape the lighting market with more efficient devices that require less power and offer flexibility in design at lower overall cost. While LED technology is way ahead in replacing conventional lighting technologies, OLED lights will follow and offer lighting solutions that we have never had before. Silver nanowire technology has begun to enable these emerging applications.

Categories Blog

Enabling SSL Adoption Through Intuitive Interconnect – Part II

Last month we discussed interconnect of the Chip on Board LED device within a luminaire utilizing a TE Connectivity (TE) scalable or Zhaga compliant socket.  This month we’ll move another layer away from the light source and look at the various device-level interconnects commonly used in lighting applications. Lighting interconnects span a broad range of options from board-to-board, wire-to-board, surface mounted and inverted through board technologies.  The multitude of interconnect options for the fixture designer can be confusing, so let’s spend the time speaking about the attributes and merits of common interconnect classifications used in lighting systems.

Board-to-board applications: This connector technology allows the direct connection of two printed circuit boards. In lighting applications, this is usually in an end-to-end fashion. While a number of board to board options exist, a specific example shown is TE’s Hermaphroditic connector. This connector allows for end to end mating of board assemblies and also allows for horizontal and vertical axis mating enabling 90° and 180° articulation.  Linear, multi-segment, solid state lighting (SSL) board assemblies commonly used in cove lighting or linear lighting fixtures are ideal applications for this type of interconnect.

Wire-to-board applications: This category of interconnection can be further segmented into sub categories; two-piece separable, one-piece removable and one piece permanent. All accomplish the same fundamental task of bringing a wire to a printed circuit board in a simple, solderless approach. An example of a separable wire to board connector can be seen in TE’s low profile, micro MATE-N-LOK connector shown in the image at the right. A one piece removable solution is best illustrated by TE Connectivity’s innovative line of poke-in connectors that includes the micro poke-in wire SSL connector. Lastly, a one piece permanent connection between a wire and board can be accomplished with an insulation displacement connector such as TE’s SMT IDC connector. Termination with an IDC connector is as simple as inserting the un-stripped wire and pressing the stuffer cap down. The common thread shared by all these wire to board connectors is they are all low-profile wire to printed circuit board connectors designed specifically  for LED lighting systems whether they be channel lettering lighting strips, general illumination LED fixtures, architectural cove and valence lighting,  or LED modules for other applications.

There is another unique wire to board product that is worth noting here as well. The inverted through-board style of connector products provide an unobtrusive interconnect to printed circuit boards. By rotating the mating axis to mate from the underside of a PCB, connector exposure and wire routing issues on the LED side of the board are minimized.  The result is a clean, minimally obstructed light emitting surface ideal for use with LED array implementations in downlight, spotlight and even street-lighting applications.

To close, the interconnection is often one of the last items to be considered in a lighting design. The wrong selection can have long term ramifications in manufacturing, reliability and field repair. With a little forethought and understanding of interconnect options, design, assembly and repair can be optimized in lighting systems. Consider the following during your design efforts:

  • Is this a board to board application? If so, can this be accomplished with a direct board to board mating connector system or is a header/wire jumper assembly required by the application?
  • For wire to board applications is a separable wire to board interconnect required or can the wire be terminated with a one piece semi-permanent or permanent connector?
  • How many circuits need to be accommodated by the connector?
  • What is the end fixture application and what are the governing agency standards required by the fixture?
  • What is the voltage and current rating required?
  • What are the particular environmental constraints required (temperature, humidity, shock/vibration, ingress protection, etc.)?
  • Does your application require positive latching or is a friction latch acceptable?