Boosting Solar Cell Power
Scientists are continuously improving the existing solar cells. Now they are taking the help of computer simulations and real lab testing. A group of physicists and engineers at MIT have discovered new methods to make the existing solar cells more efficient by 50%. Currently the most efficient solar cell gives 45% output and is extremely expensive to produce. Cells produced by using this new technology will be more efficient and cost effective. Their cost effectiveness emerges from just 1% use of refined silicon. It should be noted that refined silicon is quite costly.
Scientists want to bring clean and green energy on par with energy produced by fossil fuels. One of the biggest hurdles they face is cost. Most of the green energy is quite expensive and they have a longer break-even time. So here the MIT team has reduced the amount of extremely thin layer of silicon used in the solar cell. They are using hundreds of times less material.
Choosing Different but Simple Path:
The MIT team has paid close attention to the limiting factors of the solar cells. One of the greatest disadvantages in the existing solar cells is that whatever amount of light is falling on the solar cell has got very little time to be converted into energy. So this MIT team has concentrated its efforts on making the sunlight stay inside the cell for a longer duration of time therefore these cell can produce more energy. Peter Bermel, a postdoctoral researcher in MIT’s physics department and his team took the help of computer simulations and applied various advanced chip-manufacturing techniques.
They went for the anti-reflection coating to the front of the cell and a multi-layered reflective coating to the back of the silicon films which were ultra thin. In the end, the team settled for the best result in a multi-layered reflective coating coupled to a tightly spaced array of lines. This technique armed the cells like a laser around the cell, where light can bounce back and forth before finally exiting. This way the light stays longer inside the cell and can produce more energy. Current solar cells don’t have these coatings so the light is just reflected back to the surrounding air in the atmosphere.
“It’s critical to ensure that any light that enters the layer travels through a long path in the silicon,” Bermel said. “The issue is how far does light have to travel [in the silicon] before there’s a high probability of being absorbed” and knocking loose electrons to produce an electric current.
Trying out various combinations by computer simulations
When you have to try out various combinations and don’t know which combination will yield that magical results, its best to try out computer simulations. They will give out the excellent and almost correct results and save the time and material costs. The MIT team ran thousands of simulations with each one designed to try a slightly different approach toward keeping photons within the cell for longer. Using computer simulations they will be able to find the magical combination of multi-layered reflective coating coupled to a tightly spaced array of lines. This approach enhances the energy output of the cells by as much as 50%.
Examining the Correct combination in Laboratory
When this research team thought that they have found the right combination in the computer simulation they verified the results in the laboratory. These tests were carried out by the graduate student Lirong Zeng, in the Department of Materials Science and Engineering. According to Lionel Kimerling, who directed the project, “The experiments confirmed the predictions, and the results have drawn considerable industry interest.”
This project has caught the attention of like-minded people. Stephen Saylor, CEO of SiOnyx in Beverly, MA says, “This work demonstrates the importance of improving the performance of thin-film technologies. “SiOnyx is engaged in increasing the absorption of red and infrared light in thin silicon devices.
Bermel says that his team is already thinking of other production methods. One sound option is nanoimprint lithography, but they haven’t tried it yet. “A 35 percent efficiency increase is clearly predicted in simulations,” he opines, “but the challenge is, ‘Can you make it practically?’ That’s what we’re working on.”