Quantum Dots and 3D Printing of Semiconductors

Steve Kelly and Charles Goulding of R&D Tax Savers discuss quantum dots and 3D printing. 

Quantum dots are a relatively recent discovery in the field of semiconductors. The integration of quantum dots has immense promise to improve the performance of solar panels, LEDs and quantum computing through the use of spherical semiconducting material. Although first observed in 1986 by Alexey Ekimov and Louis Brus, more recently scientists have been exploring the application, characterization, and synthesis of this technology to improve the performance of applications such as LCD screens, lasers, and photodetectors. Recent findings indicate that the integration of quantum dot technology into 3D printing has the potential to revolutionize the fabrication of circuitry and assembly of devices by integrating sensing technologies with mechanical components. As this academic research makes a shift to industrial applications, companies in this space can utilize federal tax incentives to help support the formation of their enterprise.

The Research & Development Tax Credit

Enacted in 1981, the now permanent Federal Research and Development (R&D) Tax Credit allows a credit that typically ranges from 4%-7% of eligible spending for new and improved products and processes. Qualified research must meet the following four criteria:

• Must be technological in nature

• Must be a component of the taxpayer’s business

• Must represent R&D in the experimental sense and generally includes all such costs related to the development or improvement of a product or process

• Must eliminate uncertainty through a process of experimentation that considers one or more alternatives

Eligible costs include U.S. employee wages, cost of supplies consumed in the R&D process, cost of pre-production testing, U.S. contract research expenses, and certain costs associated with developing a patent.

What Makes Quantum Dots Interesting?

Traditional semiconductors use planar sheets of materials to create junctions between two different types of materials. These junctions allow for the control of energy flows, and in different combinations can be a source of energy, such as those used in solar panels or LED lights. Due to the precise requirements of the materials, semiconductor manufacturing is highly energy intensive and demands high precision. According to a 2010 energy analysis, semiconductor manufacturing requires an estimated 1-2% of total energy consumption in the United States alone. As the world moves toward renewable energy and green technology, more efficient methods of manufacturing will ostensibly be needed in order to minimize the amount of “captured carbon” in solar cells and LEDs. This problem is so critical that the National Academy of Engineers lists solar energy as the first of the 14 Engineering Grand Challenges.

A quantum dot can be thought of as a self-contained, semiconducting sphere. At its core, the quantum dot is a solid sphere, and the semiconductor junction is formed by layering additional material on top of this sphere. This spherical layout of semiconductors leads to immensely interesting properties. In contrast to existing semiconductors, quantum dots may be suspended in fluids. In addition, since the purity and structure may be controlled through chemical synthesis, theoretically less energy will be consumed for industrial production. Perhaps the most important characteristic is the exploitation of an effect from quantum physics. While every photon generates one electron in a conventional solar cell, in some instances a photon may generate two electrons; however, the probability of this occurring is low. Quantum dot technologies, on the other hand, greatly increase the probability of this two-for-one exchange by several hundred percent, resulting in significant efficiency improvements. Research has also shown that the size (diameter) of the quantum dot may control the emission or absorption of photon wavelength. This ability to specify precise absorption or emission wavelengths is promising for applications such as displays, lasers, and solar panels. In fact, quantum dots are already being utilized in TVs sold by Samsung to provide a wide color gamut.

Quantum Dots and 3D Printing

Quantum dots have the promise to solve one of the biggest challenges of solar cell technology development in regards to energy efficiency. By and large, existing solar panel technologies have limited efficiency within a certain wavelength, approximately 20% for commercially available solar panels. Scientists are working to increase efficiency to 50% by layering solar cells to absorb different frequencies of light. Quantum dots can be utilized to achieve this quite easily. It has been well-observed that different diameter quantum dots absorb different wavelengths of light. Since various diameters of quantum dots can be mixed together on one surface, a greater spectrum of light is able to be absorbed. While the best quantum dot solar cell is around 13% efficient, research is rapidly improving this number at a greater rate than almost any other technology. Furthermore, inkjet printing of quantum dots may allow for solar cell features to be applied to a variety of surfaces such as windows, car bodies, and other organic shapes where current technology cannot fit. Coupled with 3D printing and robotics, in the future it might be possible to spray solar cells onto buildings or cars to enable power generation at the point of demand.

Within the next decade, we may start to see quantum dot technologies as a competing alternative to solar cells. However, solar cells are just one of many applications. Since quantum dots have the ability to emit across the light spectrum, they may soon become competing alternatives to LCD screens and LEDs. Moreover, the colloidal (solid and liquid mix) property enables them to be printed by inkjet heads which is a well-established deposition technology. Also, as opposed to planar technologies, the quantum dot may be applied on uneven surfaces. Their unique properties may make it possible to apply lights or screens onto the surface of any object, rigid or flexible. This will enable applications such as flexible phones and more efficient lighting design. Coupled with inkjet technologies, quantum dots may enable the integration of small sensors onto the surface of various components to evaluate loads or displacement. Similarly, logic gates may be integrated onto surfaces. This makes them of particular interest to 3D printing where complexity is relatively low-cost and the tight integration of components can produce new and novel applications for smaller and more reliable devices and cost savings. For example, with quantum dot technology as it stands, fluorescent markers may be deposited using inkjets onto components to provide tracking or the measurement of mechanical properties. Compared to other fluorescent inks, quantum dots are significantly more stable throughout their lifespan. Generally, fluorescent inks are organic compounds with degrade overtime and in sunlight. Since quantum dots are semiconductors, they are more stable in sunlight and have low corrosive properties.

However, one of the largest opportunities for research in quantum dot technology is the material selection. The most well-researched quantum dots use cadmium and lead, both of which are highly toxic. Significant research efforts are ongoing to find alternative formulations using copper or zinc. This research is not only improving upon safety, but may further reduce the cost of the technology.

Conclusion

In the past decade, quantum dots have moved from theoretical study to more applied research for migration into industrial applications. As this research migrates from academia, significant possibilities for new applications will become available to several industries. Such research will enable whole new classes of devices and improve on existing device performance. Quantum dots are an exciting field of technology development and have the promise to greatly reduce our impact on the planet and overcome existing limitations of semiconductor technology.