Al2O3-Interlayer-Enhanced Performance of All-Inorganic Silicon-Quantum-Dot Near-Infrared Light-Emitting Diodes

Abstract

Efficient all-inorganic silicon-quantum-dot (Si-QD) near-infrared light-emitting diodes (LEDs) have been fabricated by using nickel oxide (NiO) and zinc oxide (ZnO) as the transport layers of holes and electrons, respectively. It is found that the LED performance may be significantly improved by the atomic layer deposition of an Al2O3 interlayer between Si QDs and NiO. The improvement is due to the fact that the Al2O3 interlayer can not only suppress the exciton quenching induced by the traps at the NiO surface and the accumulated holes at the NiO/Si-QD interface, but also reduce the leakage of carriers. The optimum thickness of the Al2O3 interlayer is found to be ~5.7 nm, which leads to the increase of the optical power density by a factor of ~7 (from ~2 to $14~\mu \text{W}$ /cm2) and that of the external quantum efficiency by a factor of ~10 (from ~0.01% to 0.1%) for the all-inorganic Si-QD near-infrared LED on glass. In addition, it is shown that the Al2O3 interlayer may also improve the performance of flexible all-inorganic Si-QD near-infrared LEDs on poly(ethylene terephthalate).