The evolution of LED lighting technology: from the blue LED to 200 lm/W

In a few decades, the LED has gone from a laboratory curiosity to the dominant lighting technology. This evolution of LED lighting technology has transformed not only luminous efficacy, but also colour control, lifetime and the ability to control light. This article traces the main stages and explains what they change in practice for professionals today.

The blue LED: the founding revolution

Red and green LEDs had existed since the 1960s, but the key piece was missing: the blue LED. Without it, white light could not be produced. It was in the early 1990s that Shuji Nakamura, then at Nichia, developed an efficient blue LED based on gallium nitride (GaN). By covering this blue diode with a yellow phosphor, white light was finally obtained: the way to modern LED lighting was open.

The importance of this breakthrough was recognised in 2014 by the Nobel Prize in Physics, awarded to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura "for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources". These first white LEDs already consumed up to 90 % less electricity than incandescence, without mercury unlike fluorescent lamps.

The race for luminous efficacy

Once white had been obtained, the challenge became efficacy, measured in lumens per watt (lm/W). The progress has been spectacular: whereas the first commercial white LEDs were at a few dozen lm/W, standard products now exceed 100 to 150 lm/W, and the best luminaires cross the 200 lm/W mark. Laboratory prototypes have even reached values above 300 lm/W.

This rise in efficacy changes everything for the professional: for the same illuminance, consumption collapses compared with the old technologies. We detail the issues of this performance in our article on luminous efficacy and the 200 lm/W luminaire, which is particularly decisive on solar installations.

More durable and better-designed LEDs

Alongside efficacy, lifetime has improved greatly. Progress in thermal management, component quality and power supply electronics (drivers) has made it possible to reach long flux maintenance periods, expressed by L70 and L80 values associated with B10 indices. Reliability has become professionalised, with test standards (LM-80, TM-21 method) that now frame manufacturers' promises. To go further, see our guide to assessing the reliability of LED lighting.

Optics and photometric control in clear progress

The evolution of the LED is not just about the chip. Control of photometry has progressed in parallel: precision lenses and reflectors now make it possible to direct the flux exactly where it is useful, with very varied distribution curves (narrow beams for great heights, wide for surfaces, asymmetric for façades or pitches). This native directionality of the LED, impossible to obtain so finely with the old omnidirectional sources, reduces losses and improves uniformity while limiting glare. Controlling UGR is made easier, a major advantage for visual comfort in the workplace as well as in sport.

The planned end of old technologies

This coming of age of the LED is accompanied by the gradual withdrawal of traditional sources. European regulations have set in motion the disappearance of several discharge and fluorescent lamps, for reasons of energy efficiency and elimination of mercury. For managers of lighting installations, this means that switching to LED is no longer just a matter of economic opportunity, but often a maintenance necessity: old sources are becoming difficult to replace. The technological evolution of the LED therefore comes at the right time to accompany this transition, offering better-performing solutions on every level.

Colour control: high CRI and tunable white

The first LEDs sometimes suffered from poor colour rendering and an unflattering cool white. Recent generations offer a high colour rendering index (CRI) and a wide range of colour temperatures (in kelvins). Tunable white even makes it possible to adjust the colour temperature dynamically, for example to follow the circadian rhythm in an office or adapt the atmosphere of a space throughout the day. Colour has become a parameter of comfort and well-being, not just of quantity of light.

Advanced architectures: CSP and miniaturisation

On the component side, architectures have evolved to gain compactness and performance. CSP (Chip Scale Package) approaches, which reduce the size of the package around the chip, or high-density modules, make possible luminaires that are thinner, more powerful and better controlled optically. This miniaturisation opens up new design possibilities, from very thin linear luminaires to high-power floodlights for great heights.

The connected LED: control and IoT

The most recent stage is not optical but digital. The LED is natively compatible with dimming and electronic control, which makes it the ideal medium for intelligent systems: DALI and KNX protocols, presence detection, use of daylight, programmed scenes, remote supervision and integration into the Internet of Things (IoT). Lighting becomes an active system, capable of adjusting light to actual use and reporting data. This dimension multiplies the savings made possible by raw efficacy, as we set out in our article on savings through intelligent lighting control.

What this evolution changes for the professional today

For a company, a local authority or an installer, these advances translate into very concrete benefits: greatly reduced consumption, less frequent maintenance thanks to the lifetime, superior visual comfort (CRI, anti-glare, suitable white), and operating flexibility through control. The LED is no longer a simple alternative to old sources: it is a technology platform in continuous progress.

This maturity also affects the way projects are designed. Where people used to reason in terms of simple replacement, "one lamp for one lamp", complete lighting systems are now designed, sized by photometric study and intended to evolve (adding sensors, integration into supervision, updating scenes). The LED, by its electronic and controllable nature, allows this system approach that secures the investment over time and makes it possible to adjust the installation to future needs without replacing everything.

These innovations run through all the Rexylum ranges, from the commercial range to the most demanding applications. The GALAXY HP, 170 lm/W linear luminaire, illustrates the maturity the technology has reached today: high efficacy, careful design and lasting performance brought together in a professional product.

FAQ

Who invented the blue LED that made modern LED lighting possible?

The efficient blue LED based on gallium nitride was developed in the early 1990s, notably by Shuji Nakamura. This invention, which made white LED light possible, was rewarded with the 2014 Nobel Prize in Physics, shared with Isamu Akasaki and Hiroshi Amano.

How is white light obtained with an LED?

The most widespread method is to cover a blue LED with a yellow phosphor. The mix of the diode's blue and the phosphor's yellow is perceived as white by the eye. The colour temperature can thus be adjusted.

What is tunable white?

Tunable white refers to the ability of a luminaire to adjust its colour temperature dynamically (from warm white to cool white). It is useful for comfort, well-being or for adapting the atmosphere of a space throughout the day.

Will LED lighting continue to progress?

Yes. Luminous efficacy is gradually approaching its theoretical limit (estimated at around 250 to 300 lm/W for white), but there is still real room for progress in control, connectivity, colour quality and integration into intelligent systems.

Need a photometric study?

The audit and the photometric study are the work of a lighting design office: we recommend the expertise of the Luminance Consulting agency, the lighting design office that contributes to developing our ranges of luminaires based on an in-depth analysis of the needs of the most demanding customers. Luminance carries out the audit of your installation, the DIALux study and the compliance check. Rexylum, for its part, designs and supplies the prescribed luminaires and lighting solutions: for the choice of equipment, contact us.