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  • - LEDs don't get their color from their plastic covers.

  • And you can see that because here is a transparent LED

  • that also glows the same red color.

  • The color of the light comes

  • from the electronics themselves.

  • The casing just helps us tell different LEDs apart.

  • In 1962, general Electric engineer Nick Holonyak

  • created the first visible LED.

  • It glowed a faint red.

  • A few years after that, engineers at Monsanto

  • created a green LED.

  • But for decades, all we had were those two colors.

  • So LEDs could only be used in things like indicators,

  • calculators, and watches.

  • If only we could make blue, then we could mix

  • red, green, and blue to make white,

  • and every other color,

  • unlocking LEDs for every type of lighting in the world,

  • from light bulbs, to phones, to computers,

  • to TVs to billboards.

  • But blue was almost impossible to make.

  • (dramatic music)

  • Throughout the 1960s,

  • every big electronics company in the world,

  • from IBM to GE, to Bell Labs,

  • raced to create the blue LED.

  • They knew it would be worth billions.

  • Despite the efforts of thousands of researchers,

  • nothing worked.

  • 10 years after Holonyak's original LED

  • turned into 20, then 30,

  • and the hope of ever using LEDs for light, faded away.

  • According to a director at Monsanto,

  • these won't ever replace the kitchen light.

  • They'd only be used in appliances, car dashboards,

  • and stereo sets to see if the stereo was on.

  • This might still be true today, if not for one engineer

  • who defied the entire industry

  • and made three radical breakthroughs

  • to create the world's first blue LED.

  • (dramatic music)

  • Shūji Nakamura was a researcher at a small Japanese chemical

  • company named Nichia.

  • They had recently expanded into the production

  • of semiconductors to be used in the manufacture

  • of red and green LEDs.

  • But by the late 1980s,

  • the semiconductor division was on its last legs.

  • They were competing against far more established

  • companies in a crowded market, and they were losing.

  • Tensions started to run high.

  • Younger employees begged Nakamura to create new products,

  • while senior workers called his research a waste of money.

  • And at Nichia, money was in short supply.

  • Nakamura's lab mainly consisted of machinery

  • he had scavenged and welded together himself.

  • Phosphorus leaks in his lab created so many explosions,

  • that his coworkers had stopped checking in on him.

  • By 1988, Nakamura's supervisors were so disillusioned

  • with his research that they told him to quit.

  • So it was out of desperation

  • that he brought a radical proposal to the company's founder

  • and president Nobuo Ogawa.

  • (dramatic music)

  • The elusive blue LED,

  • that the likes of of Sony, Toshiba and Panasonic

  • had all failed at.

  • What if Nichia could be the one to create it?

  • After suffering loss after loss on their semiconductors

  • for more than a decade,

  • Ogawa took a gamble.

  • He devoted 500 million yen or $3 million,

  • likely around 15% of the company's annual profit,

  • to Nakamura's moonshot Project.

  • Everyone knew that LEDs have the potential

  • to replace light bulbs,

  • because light bulbs, the universal symbol for a bright idea,

  • are actually terrible at making light.

  • They work by running current through a tungsten filament,

  • which gets so hot, it glows.

  • But most of the electromagnetic radiation

  • comes out as infrared, heat.

  • Only a negligible fraction is visible light.

  • In contrast, LED stands for light emitting diode.

  • It's right there in the name.

  • LEDs primarily create light, so they're far more efficient,

  • and a diode is just a device with two electrodes,

  • which only allows current to flow in one direction.

  • So here's how an LED works.

  • When you have an isolated atom,

  • each electron in that atom occupies a discreet energy level.

  • You can think of these energy levels like individual seats

  • from a hockey stadium,

  • and all atoms of the same element,

  • when they are far apart from each other

  • have identical available energy levels.

  • But when you bring multiple atoms together to form a solid,

  • something interesting happens.

  • The outermost electrons now feel the pole,

  • not only of their own nucleus,

  • but of all the other nuclei as well.

  • And as a result, their energy levels shift.

  • So instead of being identical,

  • they become a series of closely spaced,

  • but separate energy levels.

  • An energy band.

  • The highest energy band with electrons in it,

  • is known as the valence band,

  • and the next higher energy band

  • is called the conduction band.

  • You can think of it like the balcony level.

  • In conductors, the valence band is only partially filled.

  • This means with a little bit of thermal energy,

  • electrons can jump into nearby unfilled seats,

  • and if an electric field is applied,

  • they can jump from one unfilled seat to the next

  • and conduct current through the material.

  • In insulators, the valence band is full,

  • and the difference in energy between the valence

  • and conduction bands, the band gap, is large.

  • So when an electric field is applied, no electrons can move.

  • There are no available seats

  • to move into in the valence band,

  • and the band gap is too big for any electrons

  • to jump into the conduction band,

  • which brings us to semiconductors.

  • Semiconductors are similar to insulators,

  • except the band gap is much smaller.

  • This means at room temperature,

  • a few electrons will have sufficient energy

  • to jump into the conduction band,

  • and now they can easily access nearby empty

  • seats and conduct current.

  • Not only that, the empty seats they left

  • behind in the valence band can also move.

  • Well, really, it's the nearby electrons

  • jumping into those empty seats.

  • But if you look from afar,

  • it's as though the empty seat or hole

  • is moving like a positive charge in the opposite

  • direction to the electrons in the conduction band.

  • (soft music)

  • By themselves, pure semiconductors are not that useful.

  • To make them way more functional,

  • you have to add impurity atoms into the lattice.

  • This is known as doping.

  • For example, in silicon,

  • you can add a small number of phosphorus atoms.

  • Phosphorus is similar to silicon,

  • so it easily fits into the lattice,

  • but it brings with it one extra valence electron.

  • This electron exists in a donor level

  • just beneath the conduction band.

  • So with a bit of thermal energy,

  • all these electrons can jump into the conduction band

  • and conduct current.

  • Since most of the charges that can move

  • in this type of semiconductor are electrons,

  • which are negative,

  • this sort of semiconductor is called n-type,

  • n for negative,

  • but I should point out that the semiconductor

  • itself is still neutral.

  • It's just that most of the mobile charge

  • carriers are negative.

  • They're electrons.

  • So there is also another type of semiconductor where most

  • of the mobile charge carriers are positive,

  • and it's called p-type.

  • To make p-type silicon,

  • you add a small number of atoms of, say, boron.

  • Boron fits into the lattice,

  • but brings with it one fewer valence electron than silicon.

  • So it creates an empty acceptor level

  • just above the valence band.

  • And with a bit of thermal energy,