Nano-Scale Solar Rectenna can Achieve 70% Efficiency
7th Feb 2013
Silicon solar cells account for the majority of solar cells in the world today, and whilst they are useful and effective they actually only work at a 10% - 20% efficiency rate; some have been produced with a higher efficiency, but the cost of manufacturing is far too great to enable them to enter the market.
Scientists have theorised about a solar technology which would have an efficiency that dwarfs all other solar cells, as well as most other forms of energy generation. By using nano-scaled rectenna, a rectifying antenna, sunlight can be absorbed and directly turned into a DC current at an efficiency of 70%. Only large scale hydroelectric power plants can beat this number, and nearly all other power plants work at less than 50% efficiency.
The reason that this technology still remains theoretical is due to the problem of constructing and testing it as parts within the rectenna must be mere nanometres apart. Engineers at the University of Connecticut now plan to use a manufacturing technique called selective area atomic deposition (ALD) to create a working rectenna.
Phys.org explained that “in a rectenna device, one of the two interior electrodes must have a sharp tip, similar to the point of a triangle. The secret is getting the tip of that electrode within one or two nanometers of the opposite electrode, something similar to holding the point of a needle to the plane of a wall.”
Atomic layer deposition is defined as, “a thin film deposition technique that is based on the sequential use of a gas phase chemical process. The majority of ALD reactions use two chemicals, typically called precursors. These precursors react with a surface one at a time in a sequential, self-limiting, manner. By exposing the precursors to the growth surface repeatedly, a thin film is deposited.”
By. Henry Winter