Silicon crystal defect and solar cell performance
Updated: Jan 18, 2021
Solar manufacturing players are striving to deliver (solar cell) product at lower production cost, reliable and higher performance. To achieve this, advance solar cell technologies are now leaving R&D lab and entering the manufacturing environment, where such technologies are known as: Front contact to back contact to Silicon-based tandem to silicon heterojunction technology to passivated emitter rear cell (PERC). Aside of thin film (ie: First Solar), the major bulk of solar cell materials is: silicon.
Let’s talk about how silicon is created. First you have polysilicon charges put inside crucible and then you melt polysilicon at high temperature, and then you dip a seed and do seeding, necking and shouldering process. Then after that you keep growing the crystal slowly and grow the entire body of silicon and then after you grow tail make end cone and cooling. This silicon crystal growth technique is known as Czochralski process.
During this process of growing silicon, there are so many defects that can be incorporated inside silicon itself. If we cut the silicon crystal - the cross section from top to tail. You will be able to see different defect formation throughout the crystal length. Not all defect is bad, some of defect is harmless actually some defect can be beneficial to solar cell. Possibly could boost the solar cell performance. But the interaction between the defect and solar right now is not well understood yet.
It is critical to create and R&D characterization platform where when there is a process issues occurred at the solar cell company then we can generate the data and triggers it back to the silicon supplier and they can react, they can retune their process and they can give a better product and on top of that we will learn what defect matters most for silicon solar cells.