Lossev’s work was ignored for some time until 1951 when a better understanding of the LED light phenomenon was provided by K Lehovec and colleagues following the development of the p-n junction and theory in 1947. In their abstract they describe “Recombination of carriers injected through P-N boundaries in silicon carbide crystals may lead to light emission ("injected light emission")… The light intensity increases approximately proportionally to current…”

Following the articles by Haynes and colleagues in 1952 and 1956 the potential light emitting capabilities of the LED and potential application in the light bulb began to be taken seriously. However, up until this time the light was a very red light so a material still had to be found to create a white or warm white / yellow light.

The development of a suitable LED light for traditional light bulb replacement took a long time and even when a suitable white light or colour temperature was found the light intensity or brightness was too low. Subsequently the application of LEDs remained in solid state or electronic applications.

In 1962 when the first practical visible spectrum LED light was developed by Nick Holonyak Jr of General Electric. Then in 1972 Holonyak’s graduate student M. George Craford invented the first yellow LED and 10x brighter red and red-orange LEDs. When green LEDs then came along the applications increased with the use of three basic colours.

The breakthrough occurred in 1994 when Shuji Nakamura and colleagues from the Japanese company Nichia developed a blue high brightness LED light, which are made from indium gallium nitride (InGaN). This was significant for a number of reasons but also because when blue, green and red LED light are added together the light appears white to the human eye.

Nakamura’s invention formed the basis for future white LED light production and he was awarded the Millennium Technology Prize in 2006, but by that time had left Nichia. However, it was not until approximately 2008 when LED light output was sufficient enough to produce a light of sufficient intensity to use in residential and commercial lighting.

We estimate that it has only really been since late 2009 that 10-12W LED light bulbs have been able to match their traditional halogen and incandescent counterparts. And it has only been in the last year since 2011 and 2012 that there have been LED light bulbs rated at 7W which are considered to have sufficient light intensity (> 500lm). Examples are LED light bulbs which utilise more recent LED chips like the CREE MTG, XTE or MTG-2.

References:

The diode: The first electronic device, Electronics World, 110, 45-47

Light emitting diodes – How it started, Journal of Non-Crystalline Solids, 352(9-20), 871-880 

Characteristics of LEDs – Ch 2. Power Supplies for LED Driving, 2008, Elsevier

The long history of light-emitting diodes. Electronic Products (Garden City, New York), v 53, n 9, September 2011

Candela-class high-brightness InGaN/AlGaN double-heterostructure blue-light-emitting diodes. Nakamura et al. 1994, Applied Physics Letters, 64, 1687-1689

D Kahaner “Blue LEDs: Breakthroughs and Implications.”

CREE (2011). New Cree XLamp® MT-G LED Delivers Unprecedented Performance. CREE Press Release, Feb 22, 2011. http://www.cree.com/news-and-events/cree-news/press-releases/2011/february/110222-mt-g