Modernization of the world is marked by the innovation in Science and Technology. In recent times, there have been many technological advancements that spearhead us towards new levels of technological advancements. There has been a recent discovery of Quantum Dots that has found its utilization in the core section of Engineering and effects our day to day lives directly.
Quantum Dots (QD) are synthesized by nanoscale crystals which can transmit electrons. When UV Rays or Ultraviolet Rays strike over these semiconductor nanoparticles, they can emit light of various colors which is visible due to variation of the wavelength of light rays. The various colour patterns are due to the variation of the wavelength of light rays.
In quantum dots, properties vary according to the shape and type of semiconductor material.
Russian physicist Alexei Ekimov studied in detail over the topics of nanocrystals of Copper Chloride and Cadmium Selenide in a molten glass matrix and he also observed the fluorescence and color gradients. He is credited as the founder of Quantum Dots discovery which dates back to 1977.
Alexander Efros was the first scientist who theoretically explained the concept and Louis Brus introduced the Colloidal Quantum Dots Discovery.
Detailed Study
Quantum Dots are light emitting sources and are also evolving as better forms of LEDs, also known as QLEDs. The color of light emission depends on the difference of the gap between the Valence Band and the Conduction Band which is categorized under the Band Theory which forms the basis of categorization of material whether it is conductor, insulator, or semiconductor.
These particles are very tiny for that reason we categorise this field in Quantum Mechanics. Whenever quantum dots are illuminated by UV Rays than their electrons can get excited to a higher state of energy. It was shown that electronic wave function in quantum dots resembles the ones in real atoms. The optical properties of spherical metallic quantum dots can be explained by Mie Scattering Theory.
Properties OF Quantum Dots
Quantum dots have properties in between bulk semiconductors and discrete atoms or molecules. Their optoelectronic properties vary because of their size. Larger quantum dots of bigger diameter emit longer wavelengths, like Orange or Red, and those with smaller diameter emits shorter wavelengths of light like Green and Blue.
QLEDs versus LEDs
Quantum dot Light Emitting Diode or QLED is better than other types of LEDs because they are very small so they occupy very little space and the amount of light generated by them is brighter than normal LEDs in general.
Difference between the QLED and OLED
QLEDs are comparatively better than OLEDs because they emit more brightness and consume less energy. OLEDs are emissive which means the pixels emit their own light. QLEDs currently designed are transmissive and they fully depend on the LED backlight.
Problem Solving
The most devastating impacts of LED is that of its high power consumption and utilities can be solved using QLEDs.
Modern Day Application
These quantum dots are majorly used as QLEDs in quantum computing, but its use is limited due to its new discovery and high cost. They are also used in solar cells and forms the basis of laser emission. Solar panel is also based on Quantum Dot Theory. Single Electron Transistor and medical imaging can be accomplished using this technology. Due to its usage in fluids, we also use this in inkjet and laser printers’ ink.
Plasma or Chemical Synthesis
Plasma synthesis has been established as one of the most famous gas-phase approaches for the production of quantum dots, usually, for covalent atoms, for example, Silicon (Si) and Germanium (Ge) quantum dots have been synthesized by using non-thermal plasma. The size, shape, surface and composition of quantum dots can be hindered using this method. Quantum dots generated by plasma are in powdered form. They can also be made using Carbon. Research-based on these methods is explained below:
Colloidal Synthesis
In colloidal synthesis, the product neither precipitates as a bulk solid nor remains dissolved. It involves heating the solution at a very high temperature which is a major factor in determining the optimal conditions for nanocrystal growth. The concentration of monomers is another critical factor that needs to be controlled during nanocrystal growth. The growth process of nanocrystals can occur in two different phases, ‘focusing’ and ‘defocusing’. At high monomer concentrations, the critical size is relatively small, resulting in the growth of nearly all particles. In this regime, smaller particles grow faster than large ones as larger crystals require more atoms to grow resulting in ‘focusing’ of size distribution, resulting in a discrete distribution of particles.
Research based on Colloidal Quantum Dots
Colloidal Quantum Dots are solution synthesized semiconductors in low-cost photovoltaics. Change in solar cells absorption can take place using Tuning of Bandgaps, displaying the quantum size effects.
According to a research based on the Colloidal Quantum Dots by Jiang Tang and Edward H Sargent:
Recent progress in this field involved the reduction of cost of solar cell composition and more eminent panels are build due to the usage of colloidal quantum dots, in addition to it colloidal quantum dots photovoltaics have contributed 5% increment in the solar power conversion efficiency, achieved by the introduction of a new architecture.
Reaseach based on Carbon Quantum Dots
According to a research based on the Carbon Quantum Dots by Shi Ying Lim, Wei Shen and Zhiqiang Gao:
Fluorescent Carbon Nanoparticles or Carbon Quantum Dots (CQDs) are quality of carbon nanomaterials that have been nascently introduced and have gathered much interest in global market as a potential competitor to conventional semiconductor quantum dots. In addition to their comparable optical properties, they possess desired advantages of low toxicity, environmental friendliness low cost and simple synthetic routes. Since exploration, CQDs have found many applications in the fields of chemical sensing, biosensing, bioimaging, nanomedicine, photocatalysis and electrocatalysis.
Research based on Silicon and Germanium Quantum Dots
The result was formulated by Prof. Guo Guoping, Prof. Li Hai-Ou, team was led by Academician Guo Guoping.
They manufactured high-quality Si MOS quantum dots and achieved a record of spin qubits. Based on this technique, they found both the effect of strength and orientation of the external magnetic field on spin relaxation rates. They summarised when the in-plane external magnetic field is positioned at a certain angle, the spin relaxation ‘hot spot’ could be ‘cooled down’ by two orders of magnitude. This work had a sprawling contribution in twisting the phenomena and solving the practical problems of optimum operating conditions to exploit the spin degrees of freedom in Silicon Quantum Dots.
QLED – A Game Changer in Near Future
QLED has transformed many things to build them more efficiently. From solar cells to normal LEDs quantum dots is tangible everywhere. We hope to witness much more developments in the upcoming days.
Conclusion
To end with, I want to establish a fact that we can see new technology coming up but rarely use them because of its huge expense. However, its sprawling demand and ongoing innovation will surely depreciate its price and we will see a complete change of technology due to its widespread usage, one day.
in the current world.
I find it really interesting to read. Keep up with the great work 😊😊
Wonderful work Lakshya. Can see the depth of your knowledge in this article written by you. Great going. All the best and looking forward to your next article.