Multi-chromatic silicon nanocrystals

• Published in: Light, science & applications science & applications, 2017-06, Vol.6 (6), p.e17007-e17007
• Main Authors: Bruhn, Benjamin, Brenny, Benjamin JM, Dekker, Sidoeri, Doğan, Ilker, Schall, Peter, Dohnalová, Katerina
• Format: Article
• Language: English
• Subjects: 639/624/1107/527/1819; 639/624/399/354; Applied and Technical Physics; Atomic; Classical and Continuum Physics; Color; Crystals; Lasers; Luminescence; Luminosity; Materials science; Molecular; Nanocrystals; Optical and Plasma Physics; Optical Devices; Optics; Original; original-article; Photonics; Photons; Physics; Physics and Astronomy; Radiation; Scaling; Silica; Silicon; Toxicity
• ISSN: 2047-7538; 2095-5545; 2047-7538
• DOI: 10.1038/lsa.2017.7

Silicon nanocrystals (SiNCs) have great potential to become environmental friendly alternatives to heavy-metal containing nanocrystals for applications including medical imaging, lighting and displays. SiNCs exhibit excellent photostability, non-toxicity and abundant resources, but their often reported inefficient and spectrally limited light emission seriously impair their applications. Here we demonstrate a new method that converts SiNCs into an efficient and robust multi-chromatic phosphor. Using ~15 keV electron-beam irradiation of oxide-capped SiNCs, we introduce several types of color centers into the nanocrystal’s oxide shell with efficient blue, green and red emission bands, together yielding warm-white photoluminescence, even for a single SiNC. Introduced centers are not native to the original system and we relate them to known defects in silica. Unlike in the silica host, however, here the centers are efficiently optically excitable. Provided further optimization and up-scaling of this method, e-beam irradiated SiNCs can be of great interest as white phosphors for applications such as LEDs. Silicon nanocrystals: Efficient, environmentally friendly white-light source An efficient phosphor that emits warm white photoluminescence can be created by bombarding silicon nanocrystals with an electron beam. Silicon nanocrystals are promising for replacing nanocrystals that contain toxic heavy metals, which are currently used in displays and lighting. But their application is constrained by their inefficient and spectrally narrow emission. Benjamin Bruhn at the University of Amsterdam and co-workers used various techniques to create oxide-capped silicon nanocrystals. They then created color center defects in the nanoparticles’ oxide shells by bombarding the nanocrystals with an electron beam for a few minutes. The color centers have efficient blue, green and red emission bands, and can hence produce white light when the nanocrystals are pumped by a low-power blue laser diode. After optimization, the approach may be useful for realizing new designs of solid-state white lighting.