Archives for posts with tag: plasmonics

I recently had the opportunity (and pleasure!) of attending the 39th Photovoltaics Specialists Conference (PVSC) in Tampa, Florida. The conference, which is put on by the Institute of Electrical and Electronics Engineers (IEEE), is an annual meeting of scientists and engineers who work in the field of solar energy. PVSC attracts people from all over the world to come and share their research on some of the cutting-edge topics in the field. In this entry I will be providing some highlights of the trip, especially topics that were of interest to me.

I once again had the honour of hosting (alongside other HQP) the Photovoltaic Innovation Network (PVIN) booth. As I have mentioned in previous blog entries, the booth is where we get to represent Canada’s research in photovoltaics. A lot of companies and Universities outside of Canada do not know exactly what we do up in Canada in regards to photovoltaic research, so the booth gives us an opportunity to educate them and get them interested in our work. There are always interesting discussions to be had at the booth with researchers from all over the world!

The conference itself had a plethora of talks which covered almost every aspect of photovoltaic research. It really is amazing just how many different technologies there are for capturing light from the sun and turning it into electricity; so many that it can make one’s head spin! There were discussions on existing technology that has been around since the dawn of photovoltaics such as crystalline silicon, as well as proposals and theories for ideas that have not yet come to fruition, such as hot carrier solar cells. Two talks in particular stood out to me because of their relevance to my own research (light trapping in ultra-thin crystalline silicon). One talk, given by Nicholas Hylton from the Imperial College of London, was on using aluminum nanoparticles (microscopic spheres that are only 100 nm in diameter) for light trapping in solar cells. This type of light trapping is known as plasmonic light trapping, and a lot of research has been devoted to the field in recent years. The novelty of their approach was to use aluminum instead of the more commonly used silver and gold. The issue with using silver and gold is that although they are useful for trapping light towards the red end of the solar spectrum, they are detrimental at the blue end since they soak up a lot of the light there. Aluminum does not have this issue, and the researchers were able to demonstrate an enhancement in light absorption across the whole spectrum!

Another talk that interested me was given by Joao Serra from Universidade de Lisboa in Portugal. His talk, titled “Comparative Study of Stress Inducing Layers to Produce Kerfless Thin Wafers by the Slim-Cut Technique”, focused on the fabrication of ultra-thin (thinner than 100 micrometers) silicon wafers from thicker wafers. Using ultra-thin wafers for silicon solar cells has become attractive in recent years because of the potential to cut costs by using less silicon. Serra’s talk discussed a method for making such wafers. The process involves laying down a layer of epoxy on top of a thick wafer, then heating and cooling opposite sides of the wafer. During the heating/cooling process, a thin layer (he discussed 60 micrometer thick layers in his talk) peels away from the wafer. The advantage to this process is that thin silicon wafers can be fabricated without losing any silicon in the process. Standard wafers are usually made by sawing from a large silicon ingot; the sawing process naturally destroys useful silicon in the process.

I would have to the say my favourite technical aspect of the trip was a discussion that Martin Gerber and I had with Keith Emery, the winner of this year’s William R. Cherry Award. The award is given to “an individual engineer or scientist who devoted a part of their professional life to the advancement of the science and technology of photovoltaic energy conversion”. Keith gave me a very useful suggestion for an undergraduate lab we run here at McMaster University. The lab allows undergrads to fabricate a PERL cell, the solar cell that holds the world record efficiency for single junction silicon cells. Being a record breaking cell, it is naturally very complicated to make and students have had very little success in achieving reasonable performance from them. We shared this with Keith and he suggested that a PERL cell is far too ambitious for an undergraduate lab. He suggested instead that we make far simpler cells. Although it may appear to be a simple suggestion, it really got my thinking about how we can make the lab a better learning experience for students. I will now be working on redesigning this lab around the concept of a simpler solar cell, and owe my inspiration to Keith!

The conference was by far not the only fun part of the trip. I mean, it is summer time and we were in Florida, you can’t really get much better than that! When we weren’t attending the conference we were at the pool, wandering about Tampa, or dining at the many restaurants they had down there. On one day we went down to the beach in the neighbouring city of Clearwater. I’ve never swam in the ocean before, and I don’t think I’ve ever swam in a body of water that was that warm! Overall the trip to Florida was great, and sometimes it felt more like we were on vacation and not on a business trip! I would like to thank Jennifer Briand for organizing this excursion for us, and for all the HQP who attended for the great company and discussions we had.

Kevin's picture

-Kevin Boyd

Ph.D Candidate, Year 1

Department of Engineering Physics

McMaster University.

Hello everyone! I’m here to tell you all about my trip to Frankfurt, Germany for the 27th European Photovoltaic Solar Energy Conference and Exhibition!  I flew out of Toronto at 1pm on Saturday afternoon, and I landed in Germany at 6am Sunday morning; that’s 12am Toronto time. This was my first time travelling alone, so I was admittedly nervous about the whole experience. Flying alone into a foreign country where I don’t speak the language, and where I can’t read street signs, made the prospect of navigating my own way from the airport to my hotel a rather daunting task, but I made it okay!  At the hotel, I met up with the other members of the Photovoltaic Innovation Network (PVIN), and we set out to explore the city before our week-long conference. Frankfurt is one of the financial hubs of Europe, and it features hundreds of different banks from all over the world. It is a very international city, but also a very quiet one. At night, you don’t see too many people walking in the streets; living in Hamilton, and having spent time in Toronto, this is not something to which I am accustomed!

Frankfurt, being such an international city, made an appropriate setting for the conference. 4024 people from across 76 countries participated either by giving talks, presenting posters, or simply listening to the presentations. The conference brought a lot of different people together, and with them came a lot of different ideas. During the first few days, the presentations focused on solar cell devices, and I must say that the diversity of solar cell designs is quite amazing. There were talks on traditional silicon cells, organic cells, heterojunction cells, multijunction cells, Dye and Hybrid cells, concentrator systems and so much more! My own work involves silicon, so I was particularly interested in these talks. Silicon has been around for a long time in photovoltaics, and it is a very mature technology. I observed that a lot of the current interest in silicon is not about improving devices, but about finding ways of making them cheaper while maintaining the same performance.  For example, there were many talks on replacing the silver in silicon cells with cheaper metals such as nickel and copper. While silver has nice electrical properties that make it attractive for use in solar cells, it is also expensive and the price is somewhat unpredictable.

Later into the week, the presentations focused on the ‘big picture’ issues of solar energy. There were talks on large-scale photovoltaic power plants, grid integration, manufacturing and processing, and solar cell markets, just to name a few. These talks were interesting because they covered issues that we don’t often think about at the research level. For one, we often don’t consider the manufacturability of the devices we make in the lab. It is one thing to be able to make high efficiency solar cells one at a time in a laboratory, but it is quite another to be able to produce them in higher quantities at a large-scale factory. As a researcher, the talks I saw later in the week really put things in perspective. I saw that solar energy is not just about the research; research is only the first link in a long chain. Included in the chain are the manufacturers that mass produce cells, the engineers who build and install the systems, and the policy makers that study and regulate the deployment of these systems. There are so many contributors from across numerous disciplines working in solar energy, and the conference really reinforced that idea in me.

I must say that my favourite presentations were those by Dr. Harry Atwater from the California Institute of Technology, and Dr. Martin Green from the University of New South Wales. Both men are very prominent researchers in the field of photovoltaics, and each lead a large group of graduate students and post docs that work at the frontier of photovoltaic research. Dr. Green in particular has done some of the pioneering work in silicon cells, including making a cell that is 25% efficient. This cell holds the world record for efficiency! A neat little bit of trivia is that Dr. Green graduated with a PhD from McMaster University, where I did my undergrad and am currently working on my Master’s degree. The talks given by Drs. Atwater and Green focused on the exciting work being done to incorporate the field of plasmonics into photovoltaics. Plasmonics is a field that deals with the interaction of light with nano-sized metal structures, and the strange phenomena that can result. For example, thin sheets of metal with nanoscopic holes can be made to transmit light in one direction, but not in the opposite. For a solar cell, this means that light could enter a cell, but not escape it. A useful application, indeed!  As solar cells are made thinner, in a push to reduce cost and the amount of material used, their ability to capture light is compromised. Techniques for manipulating and trapping light then become necessary in order to maintain comparable performance with thicker cells. The field of plasmonics happens to be brimming with these techniques. I should mention that my own research involves plasmonics. I am working with ultra-thin silicon cells, and using nano-sized particles of silver as a scheme for light trapping. This is why I was especially interested in these talks. Seeing Drs. Atwater and Green speak at the conference was truly a pleasure! Considering that they are co-authors on many of the research journals that I read, it felt like I was at a concert seeing my favourite musician play!

Plasmonic nanoparticles.

 

Alongside the conference there was a solar energy exhibition, in which companies and research institutes ran booths that showed off what each had to offer. Obviously there were many companies offering just solar panels, and some had put a decorative spin on their design. For example, I saw one company that had designed the cell to have a waterfall trickling down it! Definitely something that would look nice in a backyard! Other companies were offering equipment for research or manufacturing, and these booths were the most prominent at the exhibition. The most impressive booth, in my opinion, was from a company that had actually brought a solar cell assembly line into the building. There were periodic demonstrations in which cells would be produced, ready to be used in a panel. The operators were quite secretive about the assembly line, and photography was prohibited. Our own NSERC Photovoltaic Innovation Network (http://www.pvinnovation.ca) also had a booth at the exhibition, which displayed posters that highlighted the research that we do, and the Universities and companies that are involved. Manning the booth was one of my favourite parts of the trip. At the booth, we (representatives of the Network) were able to talk one-on-one with so many interesting people, and teach them a little about what we do in Canada, and what we have to offer. We talked with students, with members of industry, and other researchers that were interested in our work. The PVIN was (to my knowledge) the only Canadian presence at the conference. I felt truly honoured to be standing there at an international convention, representing our entire country and the research that we do, all while piquing the interest of experts from all over the world. It was an absolutely amazing experience. Being there in person also showed me that interest in solar energy is a truly global phenomenon. It’s really no surprise though; the sun is essentially an unlimited source of energy!

Overall, my trip to Germany was a fantastic experience. I learned a lot at the conference, talked with many interesting people, and made some new friends with other members of the Network. I was very grateful that we all stayed in the same hotel together. Very few people had a working cell phone, so organizing trips for dinner or walks around the city would have been a nightmare had we not stayed under the same roof. The city of Frankfurt was a neat place, and according to the locals, very boring! It was mostly banks and retail stores, but we always found something to do and were never bored. Aside from the conference, food was the highlight of the trip! I don’t think I will ever be able to eat schnitzel again, because it would just pale in comparison to authentic German schnitzel. Although the trip was fun, it was also exhausting, and after a week of being away, I was excited to get home. As I mentioned before, this was my first time travelling by myself and I learned a very valuable lesson: indirect flights are no fun! I flew from Frankfurt to New Jersey, and then I had to get a taxi to New York, where I could fly back to Toronto. After 19 hours of travelling and waiting and four airports later, I finally arrived home safe and sound at Pearson! I will definitely choose my flights more wisely in the future!

Suffice to say, I really enjoyed Germany and the conference, and can’t wait for the next one! Before I go, I’d like to thank Jennifer and Sandra for all of their help in organizing the trip and making it possible! Dankeschön!

-Kevin Boyd (Year 1 of M.A.Sc in Engineering
Physics at McMaster University, Hamilton Ontario)