Advantages of Quantum dots | disadvantages of Quantum dots
This page covers advantages and disadvantages of Quantum dots including its working. It mentions Quantum dots advantages or benefits and Quantum dots disadvantages or drawbacks.
What is Quantum dots? | Working principle
The quantum dots are very small nanometer size semiconductor particles. Due to their smaller size their optical and electronic properties differ compare to larger particles. Different types of quantum dots produce specific frequencies when electricity or light is being applied to them. The frequency emitted by quantum dots can be tuned by varying the size of the dots, their shape and material used for their construction.
The figure-1 depicts structure of Quantum dots. Usually Cadmium Selenide is used as inner core and Cd1-xZnxS outer shell, coated in silica to avoid oxidation. The outer shell acts like an absorber. When a photon interacts with a quantum dot, the electron transfers from its valence band into conduction band, which leaves hole in the valence band.
The figure-2 depicts working of quantum dot solar cell. Quantum dots capture excess photon energy which is normally lost to heat generation through the process called multiple exciton generation. The incident light radiations enter through the transparent electrode of a quantom dot solar cell onto a light absorbing layer of dots in order to create electron hole pairs (e-/h+). The charged particles then seperate and eventually travel to their respective electrodes thereby producing electric current.
Benefits or advantages of Quantum dots
Following are the benefits or advantages of Quantum dots:
➨They are widely used in television industry due to ultra high definition colors and increased effective viewing angles.
➨They have capability to absorb light in order to boost output of the photovoltaics, light sensors, photocatalysts and other opto-electronic devices. Hence they are used in solar cells to produce the energy 24 hours in a day. Moreover quantum dot solar cells absorb various spectrum such as ultraviolet, visible to infrared to produce energy during day as well as night. Due to wide spectral range they make solar cells more efficient.
➨CdSe quantum dots are better compare to fluorophore dyes. They are twenty times brighter.
➨It is easy to alter wavelength of light emitted in 400 to 4000 nm range to produce different colors.
➨Quantum dot cells can be prepared via low cost solution phase chemistry methods. They are amenable to high speed printing techniques.
➨Thin layer of quantum dots on normal glass could have lifetime of upto 14 years.
➨They are compatible with chip technology.
Drawbacks or disadvantages of Quantum dots
Following are the drawbacks or disadvantages of Quantum dots:
➨CdSe based quantum dots are highly toxic and require stable polymer shell.
➨The shells can alter the optical properties and it is also hard to control size of the particles.
➨Degradation of quantum dots inside the living organism has been studied.
➨Overall conversion efficiency is lower.
➨Lower temperature operation.
➨Device production yield