LED uses p-n junction semiconductor together to produce light. Normal diode also has p-n junction semiconductor and it doesn't heats up quickly. But why LED heats up quickly. What is science behind it? And they uses same kind of material. then, how LED produces light whereas diode cannot?
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\$\begingroup\$ LED's work by exploiting the band-gap at the junction. For lower energy band-gaps, you get IR and Red spectrum LED's, design the LED with a higher band gap, and the color shifts. The heat is generated as a result of pushing current through the band gap, converting the electrical potential energy to light energy as the electrons jump from the high energy conduction band to the low energy valence band. \$\endgroup\$– R DrastCommented Sep 11, 2015 at 17:37
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\$\begingroup\$ The most simple explanation (without theory) - every process have its efficiency. You're pushing into LED 1W of power and getting 0.5W - that means the rest goes into heat (because it can't disappear). @RDrast gave more theoretically accurate explanation. P.S. Rectifier diode and LED works with different principles. \$\endgroup\$– LooongcatCommented Sep 11, 2015 at 18:30
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The amount of power going into a device such as an LED or a diode is the voltage times the current.
LEDs tend to have higher voltage drop than rectifier diodes. For example, a 1N4004 might drop 0.7V at 0.35A (245mW) but a blue LED would drop more like 3V, so it would be consuming more than 1W at the same current, and if the packages were identical it would get much hotter.
The LED will actually run somewhat cooler than you might expect because some of the power is carried off as light rather than as heat.
If the LED was 100% efficient, then it would not heat up at all- all the incoming power would be converted to light. Most LEDs are probably in the 5%-20% range, so most of the incoming power still leaves as heat.
answered Sep 11, 2015 at 17:42