It needs to be pointed out that the diode isn't converting over 100% of the electrical power into optical power. The extra optical power comes from Peltier heat drawn from the semiconductor lattice. The LEDs only had ">100% efficiency" when heated to 135°C. At 25°C the electrical efficiency was less than 1%.[1]
That still counts. Ambient temperature and pressure are necessary for just about any 'engine'. In fact, extracting heat from the environment to do something useful is more impressive than just converting one form of energy into another.
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It needs to be pointed out that the diode isn't converting over 100% of the electrical power into optical power. The extra optical power comes from Peltier heat drawn from the semiconductor lattice. The LEDs only had ">100% efficiency" when heated to 135°C. At 25°C the electrical efficiency was less than 1%.[1]
[1] Fig 1 (a) https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.108.097...
That still counts. Ambient temperature and pressure are necessary for just about any 'engine'. In fact, extracting heat from the environment to do something useful is more impressive than just converting one form of energy into another.