A typical LED diode consists of the actual light-emitting LED chip, which is surrounded by a transparent protective domed casing/lens. And while much of the light produced by the chip passes right through the casing, some of it is reflected back inwards.
Unfortunately that reflected light is wasted, as it doesn't travel out into the diode's surroundings to provide illumination. Additionally, it raises the temperature inside the diode, causing the chip to degrade faster – this means that the LED ultimately won't last as long as it would otherwise.
Seeking a solution to the problem, scientists at Imperial College London and the Indian Institute of Technology Guwahati recently developed a computer model in which a transparent layer of inexpensive metallic nanoparticles was added above the LED chip, between it and the inside of the casing.