(a) By mixing the novel photoluminescent 0D material with a yellow phosphor, the scientists were able to make a white photoluminescent film, demonstrating one of the potential applications of the material. (b) The color of the photoluminescent film could be changed by simply adjusting the ratio of the 0D material and the yellow phosphor. Image: Advanced Materials.By designing a novel photoluminescent material that is cheap to fabricate, does not use toxic starting materials and is very stable, scientists at the Tokyo Institute of Technology in Japan have enhanced their understanding of the quantic nature of photoluminescence. They describe this novel photoluminescent material in a paper in Advanced Materials.
Understanding and mastering the generation of light could allow researchers to build and improve upon all kinds of optical and electronic devices for various applications. Quantum dots (QDs) are specially tailored nanoparticles that emit light at certain frequencies when excited. But their applications are currently limited due to a combination of factors: it is hard to fabricate QD thin films, they use toxic starting materials like cadmium and lead, and they are expensive to synthesize.
Some photoluminescent zero-dimensional (0D) materials (in which electrons are confined to a few nanometers and can be excited to produce light) have also been tested, but they still rely heavily on lead. Now, scientists at the Tokyo Institute of Technology, led by Hideo Hosono, have managed to design a novel photoluminescent lead-free 0D material and analyzed it to gain insight into the nature of photoluminescent materials.
The fabricated material is made up of cesium, copper and iodine (Cs3Cu2I5) and has a crystalline structure. The cesium atoms confine the [Cu2I5]3- units, which emit blue light when excited at specific frequencies similar to those that excite QDs. The researchers were able to fabricate a thin film using this material, which proved to be very stable and had excellent photoluminescent characteristics. "The thin film exhibited good stability under ambient conditions, that is, no noticeable degradation in photoluminescent quantum yield (PLQY) over two months," states Hosono.
The team then went one step further and demonstrated two applications for this material. The first application was a white luminescent film, fabricated by mixing the blue-emitting material with a yellow phosphor at a specific ratio to produce white light. Films that emit light of different colors could then be prepared by simply varying the ratio of the ingredients used.
The second application was a blue LED, which unfortunately exhibited a poor electroluminescence (EL) performance. However, this allowed the team to better understand the underlying EL mechanisms, which will be useful in future research. "The exploration of low-dimensional compounds based on a Cu(I) halide proved to be a novel route to obtain a lead-free high-PLQY luminescent material," concludes Hosono. Such materials will hopefully see the light of day in future optical and nanotechnological applications.
This story is adapted from material from the Tokyo Institute of Technology, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.