Diameter of crystal can be several cm, why isn't it possible to make LED with larger emitting area? I've also read that emitting area of single OLED can be pretty large, but why?

  • $\begingroup$ Probably first and foremost just a matter of cost. Why use a big crystal when a small one will do? And if one simply wants a large apparent lighted surface on the LED, that's already easily being done by turning the transparent plastic encasing the LED into one big lens. $\endgroup$ – Samuel Weir Dec 29 '16 at 21:02
  • $\begingroup$ @SamuelWeir I also think that OLED can have big area, because transparent ITO anode covers all the surface, but it's a suggestion. I wonder if there are researches on this topic or someone have tried to make huge LED in a lab $\endgroup$ – Autiarii Dec 29 '16 at 21:33
  • $\begingroup$ I'm an optoelectronics engineer but not a device designer. Based on that experience, I'd guess it's a matter of defects. A single defect (google to find out the different kinds) can ruin the whole device. Defects per wafer is roughly constant (given good process control in manufacturing), so the number of bad devices per wafer is roughly constant. So as you reduce devices per wafer, your yield (fraction of devices that are good) goes down. (which means cost vs area is even worse than you'd predict from just assuming cost per wafer is constant). $\endgroup$ – The Photon Dec 30 '16 at 0:26
  • $\begingroup$ Why do you need a larger area? And don't forget heat dissipation from the engineering issues to solve. $\endgroup$ – Jon Custer Dec 30 '16 at 0:28

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