Full-color display by upconversion nanocrystals

08 Apr 2015 NUS scientists have developed novel upconversion nanocrystals capable of emitting any desired colour(s) on demand by a new concept of upconversion process.

Producing luminescence materials with tunable emission colors that can be applied for high quality displays is a very difficult task. It is challenging to develop light-responsive materials that are possible to produce any desired colors in a broad spectrum range on demand through the use of a simple external stimulus.

A team led by Professor LIU Xiaogang from the Department of Chemistry in NUS has now achieved this goal by exploiting a novel concept, non-steady-state upconversion, based on the design and synthesis of lanthanide-doped core-shell upconversion nanomaterials. In this work, the emission color of the core-shell upconversion nanocrystals was turned by adjusting the pulse width and intensity of near-infrared laser excitations. With a rational designed multi-layered core-shell structure, the core-shell upconversion nanocrystals can emit three primary colors (red, green, blue) with tunable ratios and intensities (see figure).

The ability of emitting variable emission colors on demand allows researchers to demonstrate full-color volumetric 3D displays with wide-color gamut and high spatial resolution by using this newly designed upconversion nanomaterials. This work provides a major step towards the precise control of color emission and will offer great potential in a wide range of applications such as optical memory, multiplexed optical chemical sensing, anti-counterfeiting and so on.

Figure shows (on the left) Upconversion emission spectra and emission photograph showing the ability of emitting visible RGB color by using the core-shell upconversion nanoparticles. (On the right) Luminescence color images showing the ability of display color objects using the as developed the nanocrystal/PDMS composite display matrix. [Image credit: Xiaogang LIU]

Reference

Deng R, Qin F, Chen R, Huang W, Hong M, Liu X. “Temporal full-colour tuning through non-steady-state upconversion” Nature Nanotechnology 10 (2015) 237.