This report identifies and describes the main types of LEDs in automotive applications, and their evolution.
It starts with discussing the development and future projections of physical parameters like input power, luminous flux, flux density, and thermal flows for white LEDs for headlighting, and coloured LEDs for signalling. LED evolution is approaching a saturation in the foreseeable future, so competitive advantage will shift away from these physical characteristics. Instead, LED innovations enabling new or strongly improved applications are sharply growing in importance: miniaturisation and digitalisation, plus possibilities offered by new wavelength ranges.
A decade ago, white LEDs for headlighting illumination were in their embryonic phase with very simple products including a connector and thermal and mechanical interfaces to enable reliable operation of the LED dies positioned on such a device. The next generation of white headlight LEDs were designed as SMDs for direct soldering onto PCBs. A next big evolutionary step was driven by the car industry seeking light sources supporting the development and commercialisation of matrix and ADB front lighting systems. In response, the LED industry brought forth two innovative solutions: single-die SMD LEDs with a very small footprint for extremely narrow spacing on circuit boards; and SMD LEDs containing 2-5 dies, each individually addressable to support matrix applications. A further evolution was the creation of digital light enabled by pixellated LEDs. The first such products with more than one kilopixel were announced in 2020; a further significant increase in pixel count with up to 25 kilopixels is projected for 2023.
Another important trend of car industry is to reduce the height and size of headlight cavities. To keep adequate illumination levels, high-luminance LEDs have been developed (despite their non-optimal efficacy).
For signalling applications, LEDs were already in use before the turn of the century. A new technology has been developed based on the same principle as with white LEDs: the radiation of a high-energy, low-wavelength LED die is covered with conversion phosphors to create light of the desired colour. Phosphor-converted LEDs like this deliver higher efficacy and relatively little intensity degradation over the entire operating temperature range.
The configuration of signalling LEDs over the years has shifted from mechanical clinch frames to SMD for PCB soldering. Another application trend is the launch and use of standardised replaceable LED light source modules—”LED bulbs”, so to speak. The current generation of these modules was first commercialised in 2018, and they’re on their way to high-volume application notably in mass-market, popular-priced vehicles.
RGB LEDs are unlocking opportunities for innovative interior ambient lighting. For premium cars the expectation is that in the next years more than 300 RGB LEDs will be installed to create time- and space-dependent, variable-colour lighting in the cabin. A key question for car makers is how to control the colour impression in view of varying parameters like binning batches, temperature dispersion between the three colours, and ageing. A consortium of companies named ISELED have developed solutions for this problem, greatly facilitating the use of sophisticated RGB cabin lighting.
Another innovative technology still in the research phase involves displays based on RGB microLED assemblies.
With the ongoing trend for automakers to install sensors for better-performing driver-assistance and automated-driving systems, the LED industry has been launching and developing IREDs (infrared-emitting diodes) to grasp this business opportunity. Another significant business opportunity has arisen at the other end of the light spectrum, accelerated by the coronavirus pandemic: disinfection of vehicle interiors has become a top priority, and there’s been considerable developmental effort toward UVEDs (ultraviolet-emitting diodes) which can radiate in the required UV-C wavelength range for efficient cleaning of surfaces and air flow.
Finally, this report gives an overview of the main automotive application areas and describes where the various LED types are deployed to generate the best value for automakers, suppliers, and end users.