Automotive LED take-up hinges on cost reduction

The LED is one of the optical components that will be increasingly used in cars, providing improvements to safety and design. While significant market penetration has already been seen through automobile internal lighting with standard LEDs (table 1), their high-brightness counterparts will benefit from the next big market opportunity: external rear- and front-lighting systems, such as headlights, low beams, turning lights, sidelights and daytime lamps. This area is a fashionable research topic, with emphasis directed toward decreasing price and increasing performance.

The low power consumption and long lifetime of LEDs are attractive features for automobile designers. For example, the typical LED lifetime of 10,000 hours greatly exceeds the 3000 hours stipulated for low-beam lighting. The spectral quality of white LEDs, with an associated color-rendering index of 85, combined with their small size - which creates more flexibility for designers - offers further advantages. And LEDs, which have a 250 ms faster lighting-up time than conventional bulbs, can also prevent some car accidents: the stopping distance of a vehicle traveling at 100 km/h following a car fitted with LED-based brake lights is reduced by 7 m.

However, today s LEDs still have a number of drawbacks. Most crucially, they don t deliver enough lumens per watt for external lighting, while the high cost of white and blue high-brightness (HB) LEDs prohibits significant market penetration. Also, the operating temperature of LEDs is restricted to below 100 °C, which is too low for automobiles and well below the 200 °C figure of conventional bulbs. The performances and prices of commercially available HB-LEDs and the cost requirements that must be met to enable greater diffusion into the automobile market are summarized in table 2.

According to the Optoelectronics Industry Development Association, it will be 2010 before the cost-to-performance ratio falls to the 10 $/klm (or 100 lm/$) level that is required by car manufacturers. The car industry s take is more optimistic, with HB-LEDs expected to feature in high-end cars in 2007. The industry claims that headlamps will require between 15 and 50 LEDs to achieve the necessary functions. The lamps must comply with legislation dictating that low beams and high beams, which vary only in light-intensity distribution, must deliver between 350 and 1000 lm.

Industry regulations present another difficulty: currently only the US permits LED usage for front lighting. However, Japan and Europe should follow suit, with Europe expected to allow LED-based low-beam lighting in 2007. Audi has pioneered the use of LED technology and last year it launched a new version of the Audi A8 that was fitted with front lights containing five Luxeon LEDs generating a total output of 350 lm - powerful enough for daytime running lights, but insufficient for low- and high-beam applications.

The HB-LED market for automotive external lighting is in its infancy, but we expect that it will expand at a compound annual growth rate (CAGR) of 72% over the next four years (figure 1). By 2009 the white HB-LED market will be worth $90 million, with Lumileds, Osram, Nichia, Toyoda Gosei and Cree competing for market share. By comparison, the market for internal automobile LED lighting, valued at $350 million in 2003, will increase with a CAGR of only 5% through 2009.

LEDs are also suitable for rear-lighting applications, such as center high-mounted stop lamps (CHMSLs) and LED-based rear combination lamps (LED-RCLs) incorporating tail, stop, indicator and reverse functions. Today, red HB-LEDs are increasingly used for rear lighting, and have already been fitted on 18% of new European cars. These LEDs were first fitted into CHMSLs in the 1990s, and we expect that by 2010 they will feature in brake lights installed in more than half of all cars. This year, Hella - a Germany-based manufacturer of electronics and lighting products for the automotive industry - will launch the first RCLs solely containing LEDs. We expect that within five years, 10% of cars will be fitted with LED-RCLs. The future will also see the development of smart rear lighting. By 2010 we expect to see cars fitted with LED-RCLs featuring brake-force display, a system that will react to road and driving conditions with actions such as the automatic activation of hazard lights, increasing the lit brake-lamp area, or flashing of the CHMSL.

Photonics is part of the solution for increased safety, greater comfort for drivers and passengers and improved aesthetics in cars. However, because any changes are restricted by strong regulations within the car industry, the typical time taken to implement a new standard is at least five years. This sluggishness means that car, system and chip makers must work together to further HB-LED deployment in cars. Actions such as Audi s launch of the first car with LED-based daytime running lamps will, we hope, inspire other manufacturers to investigate the potential of solid-state lighting. LED penetration has already been realized in rear lighting, with a growing number of luxury cars now fitted with integrated LED-based lamps. Cars with LED-based rear combination lamps are expected to impact the market shortly.

• The European Photonic Industry Consortium and Yole Développement report Opportunities & Challenges for Photonics in the Automobile is now available. E-mail David Jourdan at jourdan@yole.fr.