nanoHUB U Nanophotonic Modeling/Lecture 3.19: Plasmonic Nanoparticle Light Trapping
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[Slide 1]  Hey everyone. Welcome to Lecture 3.19. So, in the last lecture, we were just talking about how we can model different experimentally observed plasmonic light trapping structures for crystal and silicon photovoltaics and so now, we're actually going to explore more details of how we can fully understand and then optimize these sort of light trapping structures. 

[Slide 2] And so this is kind of quantifying what is the enhancement of absorption associated with adding the silver nano-particles which we identified last time as the most promising type of structure for enhancing absorption. And you can see that with the nanoparticle, we can have absorption up to 65% at wavelengths that are very close to the band edge because of this extraordinary field enhancement and confinements. Whereas, if you did not have this sort of light trapping then it's almost an order magnitude weaker absorption. So you basically increase from 10% up to 65% with the assorted nanoparticle. 

[Slide 3] And so, then, just zooming in again on the field enhancement, you can see that the field enhancement, with the nanoparticle, it's like this. Without the nanoparticle, it's actually like quarters magnitude smaller. 

[Slide 4] So this is like really strong, significant effect and so another way to look at it kind  of zoomed out from the previous picture. It kind of looks like this and so you can see that there's a big enhancement over the whole volume of the crystalline silicon which might be like two microns thick. 

[Slide 5] And then, if you look at this as a function of texturing height, then you can see that, actually, with the plasmonic nanoparticle, especially for very short structures, that there's a marked improvement. But then the gap kind of closes as you increase the height to a large enough value. So, that indicates that over the whole spectrum, it may not be extremely beneficial for a very thick structure. So, say, like a crystalline silicon wafer. But then or a crystalline silicon thin film where texture heights are limited to less than one micron, then this could actually be a big benefit, or a big boost. 

[Slide 6] And so just to kind of visualize like what kind of outputs you got from these sort of systems, again you have the parasitic loss, quantified as basically subtracting 3.7 from the ultimate JSC that's possible. And then of course you have some reflection losses of about 5 mA per square centimeter, but you are still left with a surprisingly large value of 36.6 mA per square centimeter, which of course is below kind of the maximum theoretical value. for silicon. But it actually comes not too far away from some of the world record wafer based crystalline silicon cells. So that says at least in principle this sort of light trapping could allow you to reproduce the performance of crystalline silicon wafer based cell with much less silicon. 

[Slide 7] This is just showing like what the texture looks like for the system.