This is a Silicon Cell
So what’s the major aspect of solar energy that’s really holding it back? Don’t know the answer?
Well I’ll tell you, it’s efficiency.
Efficiency of silicon solar cells at the moment is limited to around 30%. That’s not a lot when you think about it. That means 70% of the sunlight that’s hitting your panel is completely wasted.
So why is it wasted, and why can we not figure out a way to utilize more?
Well first you need to understand a bit of the science of how silicon solar cells work… Nope, not gonna get into a long winded discussion right here, if you would like to know more about that please visit Solar Energy Facts.
The problem is that most of the energy coming from the sun is just to high to be turned in to usable energy. Hot Electrons is the term used to define this energy and it is lost as heat during the conversion process. Enter Quantum Dots! Sounds like a new candy!
Here’s the theory behind quantum dots, or semiconductor nanocrystals as some like to call them. If you were able to separate the higher energy from the sunlight “hot electrons” and be able to capture them, the efficiency of a solar power system could be increased to a theoretical 66%. That’s more than doubling the efficiency, which amounts to a whole lot more energy.
According to Xiaoyang Zhu, professor of chemistry and director of the Center for Materials Chemistry, “There are a few steps needed to create what I call this ‘ultimate solar cell,’”. “First, the cooling rate of hot electrons needs to be slowed down. Second, we need to be able to grab those hot electrons and use them quickly before they lose all of their energy.” This is where quantum dots come in, it has been shown that hot electrons can be slowed down in semiconductor nano crystals. So that’s the first step, for the second, how to take those hot electrons out, Zhu’s team has discovered that they can be transferred from photo-excited lead selenide nanocrystals to an electron conductor made of widely used titanium dioxide.
So in a nutshell the sunlight comes in and the higher energy “hot electrons” are grabbed and slowed down by lead selenide nanocrystals (quantum dots), and transferred to an electron conductor, which allows the system to work with them instead of just casting them off as heat like conventional silicon solar cells.
Zhu cautions that this is just a first step and theirs still a lot of engineering that needs to take place before any technology is viable, but hey, it seems like a lot of good progress to me.
Resource: University of Texas at Austin (2010, June 18). Highly efficient solar cells could result from quantum dot research. ScienceDaily. Retrieved June 18, 2010, from http://www.sciencedaily.com /releases/2010/06/100617143930.htm
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