Researchers at Koç University in Istanbul, Turkey, have created relatively efficient LEDs with quantum dots suspended in a liquid. The researchers noted that the efficiency of emission from quantum dots is known to be reduced when they are taken out of a liquid and then fixed into a solid form. This loss of efficiency is known as the host material effect. So, the researchers simply integrated liquid into LEDs to eliminate the host material effect. They achieved a luminous efficiency of 64 lm/W for red, green, blue (RGB)-based and 105 lm/W for green, blue (GB)-based white light generation.
According to their theoretical calculations, the luminous efficiency of liquid QD-LEDs could reach above 200 lm/W. The researchers also noted that the optical properties of the fluid medium can be altered by replacing it with another one, and the spectra can also be modified by controlling the blend ratio of the fluids.
Koç University Researchers Increased Efficiency More Than 50%
They demonstrated that the using the liquid-based quantum dot solution increased the luminous efficiency by more than 50% due to suppressed host material effect. Second, as the quantum yield of the quantum dots increased, they pointed out that ratio of the number of emitted photons compared to the absorbed photons improved significantly, which lead to a more efficient color conversion and higher efficiency of the white LEDs.
They performed additional fine-tuning of the color conversion spectra to keep the peaks close to the peak of the eye sensitivity function. This additional fine-tuning led to the high luminous efficacy of the optical radiation and high luminous efficiency.
They published the results in the Optical Society journal Optica.