Excellent article about QDs, and we are included, with interesting quotes from Art.
Trends in Miniaturization
Yet another quantum dot implementation comes from Quantum Materials Corp. of San Marcos, Texas. The company is a nanomaterials supplier, making tetrapod quantum dots. As the name implies, these quantum dots consist of a core and four arms. Adjusting the dimensions of either the core or the arms alters the spectral output, leading to the possibility of emission over a range of wavelengths and amplitudes.
Quantum Materials has produced quantum dots made out of heavy metals, such as cadmium, and is developing others with zinc and indium cores. An advantage of the latter is that the materials are nontoxic, which keeps potential toxicity issues from arising during manufacturing, use and eventual recycling.
Although the cost of quantum dots is confidential, there is some information that illustrates just how expensive these nanocrystals can be. The publicly known cost runs some $2000 a gram, 50 times as expensive as gold, according to Art Lamstein, director of marketing at Quantum Materials.
Such prices impact the use of quantum dots. However, Quantum Materials believes it has a solution to this problem. “We’ve developed and commercialized an automated process for the synthesis of quantum dots,” Lamstein said.
Besides substantially cutting the cost of production, automation brings another benefit, he added. It tightens the performance-defining attributes of the quantum dots by eliminating variations in size and shape introduced during manual processing. The result is that optical and other characteristics should be much more predictable, which could contribute to the yield of any product.
Quantum Materials has a subsidiary, Solterra Renewable Technologies, that is commercializing the technology in solar cells. These will be thin film and made in a roll-to-roll press, with the quantum dots embedded in a polymer using a proprietary process.
As for miniaturization, one possibility would be quantum dots sitting atop a conductive layer, Lamstein noted. Instead of working via photoluminescence, as all current quantum dot sources do, these devices would excite emission through electroluminescence. A key advantage would possibly be higher efficiency, as there would not be a multistep “electron to photon to downshifted photon” process by which the light is produced.
Such a device is an industry goal, according to Lamstein. Pulling it off would require creating a conductive and quantum dot layer such that electrons could be efficiently injected from the first to the second while keeping each intact. The quantum dot itself would need to be carefully crafted so that it would have a long life without developing surface defects and without the matrix developing heat-related color change.
“An electroluminescent device would be brighter, smaller, more efficient with less heat generated, less expensive to manufacture and open to many form factors. We think we have the material for it,” Lamstein said.