But unfortunately, the usage of broad spectrum white LED street lamps at night pollute the night sky with light in such a manner that renders powerful research telescopes useless.
They decided to preplace their old yellow light emitting sodium street lamps with yellow emitting LED street lamps, as the sodium street lamps are being phased out due to loss of production.
But this solution created another problem, yellow LEDs are not efficient nor bright.
This solution solved the telescope problem but inadequately lights the streets in La Palma at night efficiently.
This inefficiency arises from the fact that present day yellow emitting LED technology is merely a shifted and thus degraded red LED technology that is somewhat un-naturally forced to emit yellow light. Yellow emitting LEDs can also be made from a phosphor-down-conversion. This method results in an wavelength broadened yellow light derived from a degraded blue emitting LED technology.
Consequently, there is the need to invent a new and optimized specifically yellow emitting LED technology that is efficient and bright.
For example, the graph pictured above is called a energy band diagram. It graphs the allowable energy ranges for charge carriers, in this case for the material Copper (I) Oxide. This graph also compares the wavelengths of the charge carriers in the material to the atomic spacing wavelength of the material itself. If such a graph forms a smile at the top where the smile's lowest point aligns directly over the frown's highest point, then this material is a GREAT CANDIDATE for an LED, and in this case, it does.
Also, note that the graph pictured above shows a match for charge carrier energy potential loss that is equal to a YELLOW PHOTON. In other words, Copper (I) Oxide semiconductor can efficiently and directly emit pure yellow light and could be considered one of the viable candidates for the next generation yellow emitting LED.
I therefore propose that research on developing and producing an optimized efficient yellow emitting LED technology begin now.