A silicon quantum-dot (Si QD)-based hybrid inorganic/organic LED that exhibits white-blue electroluminescence (EL) and is fabricated by solution processing has been developed by a group at Hiroshima University (Hiroshima, Japan). The QDs were fabricated using pulsed laser ablation of a crystalline Si wafer placed in a 1-octyne solvent fluid; it took several 8 h periods to create enough Si QDs, which were then filtered through a membrane with a 100 nm pore diameter and dried under vacuum.
To fabricate the 4 mm2 LED, hole-injection and hole-transport layers were spun onto a prepatterned indium-tin-oxide (ITO)-coated glass substrate, with the ITO forming the anode. Subsequently, a 66-nm-thick Si QD emission layer in a solution was spin-coated and thermally annealed, followed by an electron-transport layer and a cathode. The LED produces a spectrum (red line is original data; black line is fitted) that has a small amount of EL around 2 eV (620 nm), increases sharply at 2.5 eV (496 nm), and peaks at 3 eV (413 nm). The output is about 78% from the Si QDs, with the rest coming from the organic matrix. The researchers determined that the very uniform light emission of the LED, in contrast to that of a purely organic LED, was due to the addition of the Si QDs.
Reference: Y. Kin et al., Appl. Phys. Lett. (2015); http://dx.doi.org/10.1063/1.4921415.
