Quantum Dots… They Are In Your Future

Hunter McDaniel and Aaron Jackson
UbiQD
Café Scientifique- Los Alamos

Description

Written by Elijah Pelofske

 

 

 

 

 

 

 

 

 

The speakers began by introducing themselves and their background. Both Hunter and Aaron got their PhDs in Material Science, and Hunter founded the start up UbiQD in Los Alamos in 2014. Aaron is one of the team members at UbiQD, and currently there are 12 full time employees.

The purpose of UbiQD is to use quantum dots to better harvest sunlight. Quantum dots can be thought of in terms of a photoluminescent demonstration. Blue light when shown on some photoluminescent paper is re-emitted from that paper in the form of green light for a small period of time. However, when compared to shining red light on that paper, the light re-emitted is very small and difficult to discern. What this means is that blue light is higher energy than red light. Quantum dots function in a similar manner—when a very specific frequency of light hits a specifically manufactured quantum dot, that quantum dot absorbs and then re-emits that light at specific frequency. The frequency that the light is re-emitted at is entirely determined by the size of the quantum dot. The smaller the quantum dot, the smaller the frequency (such as blue light.) Larger quantum dots produce more red light which has a larger frequency.

One of the applications of quantum dots is that they can very accurately produce one color of light. LEDs and quantum dot LEDs can be manufactured to have a specifically desired emission spectrum. It is very important to produce exactly the correct color, and there are many many colors that exist. The Hue scale, which can be visually represented by a cylindrical coordinate system, very accurately described all of the possible colors. The advantage of quantum dots is that they can reach a larger volume on that hue scale than traditional means of lighting.

In addition to more accurate colors, quantum dots are much easier to manufacture. UbiQD specifically manufactures quantum dots which are non-hazardous, they are based on zinc and copper instead of elements like Cadmium. Quantum dots also have applications in security inks for monetary authentication, and harvesting sunlight more efficiently. Currently this is what UbiQD is focusing on—manufacturing quantum dots for windows where the edge of the window can have solar cells on the side of the window which can convert the sunlight of a particular frequency filtered from the quantum dots, and retained in the window due to total internal reflection. About 70% of the sunlight that comes through the window can reach the edge of the window. Additionally, UbiQD is also testing some plastic strips that can be applied to greenhouses, which can change the profile of frequency versus intensity graphs. The idea behind this is to more accurately mimic the absorption spectrum of chlorophyll for all times of the year. Because of the precision of creating an emission spectrum using quantum dots this is not extremely difficult to do, and can lead to an increase in production output form the greenhouse for all times of the year. Currently, these products are being tested in northern New Mexico green houses.

Hands on Activity

 

The hands on activity for this café was a color differentiating task. This demonstrated the difficulty in distinguishing slightly varied hues.