University of Toronto researchers have produced the first tunable pure green-blue emitting LEDs from colloidal cadmium selenide nanoplatelets. The very nary bandwidth of the light emission makes even a change of 10nm easily detectable. Such LEDs could be integrated into ultra-high-quality displays with significantly improved colors.
Colloidal nanoplatelets are quasi-two-dimensional quantum wells. The colloidal nanoplatelets that the researchers fabricated emit light over the extremely narrow bandwidth of around 10 nm. However, the emission wavelength of these materials cannot be easily controlled. The wavelength of light they emit depends strongly on the thickness of the atomic layers.
The researchers alloyed cadmium selenide nanoplatelets with cadmium sulphide at high temperatures in solution to overcome this problem. The team was able to make LEDs from the nanoplatelets. The structures had sub-bandgap turn-on voltages of 2.1 V for devices emitting at 2.4 eV. At the same time, they emitted the narrowest wavelength range of around 12.5 nm ever reported for colloidal semiconductor-based LEDs.
Team member Mayuran Saravanapavanantham noted that the color emitted by their LEDs is the purest ever for such materials and the purest green for any LEDs.
Researcher Fenglia Fan says that having such pure emitters in the green-blue range would allow engineers to make devices that emit a larger array of colors in the green-blue portion of the electromagnetic spectrum for higher quality displays.
The researchers published the findings in Nano Letters.