by Michael Crowley
The once assumed fact, that Photovoltaic (PV) solar technologies could not be cost effective and energetically viable, is slowly crumbling. Relatively low-cost and powerful solar cells are produced in large quantities throughout the world, making the levelized cost of electricity (LCOE) of these cells competitive with other energy-related technologies. A similar thought process was assumed when discussing the possibilities for ion implant technology in solar applications. This assumption is slowly being proven wrong too. Ion implanting technology is slowly becoming a favorable method for doping formation in semiconductors (silicon is commonly used in present PV cells). By using this technique, higher-efficiency solar cells can be mass produced. Two hurdles must be faced in order to make this technology more accessible: high costs and low throughput. These hurdles have been faced most head on by a semiconductor company, Kingstone. By developing a simpler ion implanter, Kingstone believes they can cut 90% of their current operations cost while producing a very high thoroughput (>1500 wafers/hour).
Researchers in Shanghai, looked into the possibilities for ion implanted solar cells and the ability for ion implanters to become low cost but high throughput options. If doping is needed more than once, ion implantation has clear advantages. Fewer steps are required in the workflow and efficiency loss at each step is limited. Ion implementation, which produces cells with an average of ~21% efficiency, avoids the <0.1% efficiency losses often found when using laser edge isolation (eg. plasma etching) and this number increases as surface size increases. For standard p type cells, ion implantation shows similar performance with conventional techniques.
Ion implantation allows for the ability to use uniquely single sided doping. This enables easier and simpler production in n-PERT and IBC cells and will result in higher efficiencies in both mediums. In a forming one specific type of n-PERT cell, poly-Si, ion implantation will boost average efficiency in those cells to over 22%. In IBC cells, that number will be raised to nearly 22.5%, confirmed by a third party test. Commonly used in the semiconductor industry, ion implantation, and the range of possibilities that comes with the technique, is now primed to be fully utilized in the solar industry.
Jin, G., Sun, Y., Wang, Y., Zhang, D.W., Chen, L., He, C., Boeker, J., Hong, J., Chen, S., Liu, R., Lv, Y., and Chen, J., 2016. Ion Implant Technology for State-of-the-art High Efficiency Solar Cell Applications. 2016 16th International Workshop on Junction Technology (IWJT), 59-63.