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Summer 2011 Blog - Jason Zhang

Jason Zhang has been working on the development of solar cells at the Chinese University of Hong Kong.

 

July 5, 2011

Professor Xiao's Solar Energy Lab at the Chinese University of
Hong Kong.

Greetings! For the past month I have been working in Professor Xudong Xiao’s Solar Energy Research Laboratory at the Chinese University of Hong Kong. The first couple weeks were a bit hectic, as I did not yet have a good understanding of what it was the lab group did exactly, and the language barrier did not help. Although I can speak Mandarin relatively well, translation of technical and scientific terms from Chinese into English is still a difficult task. So for the most part of the first two weeks, I was asking many, many questions and reading many, many papers. As I got to know more people in the lab and figured out what each person was in charge of and what they did on an every-day basis, I got a better understanding of the whole solar cell fabrication process in this lab. Several of the graduate student researchers helped me to figure out how I could best fit into their process, without them having to take too much time out of their schedule to accommodate me. My goal in these two months is to learn as much as I possibly can about their research, as well as contribute something to their research projects.

A view of the main lab room

The main focus of our lab is to design higher efficiency CIGS solar cells. A CIGS solar cell has many components, the most important of which is the CIGS layer, made of Copper, Indium, Gallium, and Selenide. However, the other layers are also important. They consist of the glass substrate base, the Molybdenum back contact film, the Cadmium Sulfide n-type semiconductor, and the front contact/anti-reflective layer. In general, each graduate student is in charge of one part of the cell, so I am able to work with different people.

Clearly, the goal of this research is to improve the efficiency of the CIGS solar cell. As of right now, the record efficiency for an experimental cell is around 20%, fabricated by the US Department of Energy’s National Renewable Energy Laboratory (NREL). Our goal is to, of course, beat that efficiency, or reach it with less material. CIGS solar cells are the most promising alternative to silicon crystal solar cells, and they are thin-film cells, meaning they can be made with less material and are more flexible. They have the potential to make solar energy the dominant alternative energy source in the future.

July 20, 2011

Equipment used to fabricate solar cells

In the past few weeks I’ve gained a lot more experience and familiarity with the technical equipment in the lab. I’ve found that operating a vacuum system is one of the most precise and frustrating things in the lab. If any mistake occurs within the vacuum system, the internal compartments all have to be returned to room pressure, opened, fixed, and then re-vacuumed, which takes at least one full day. I’ve also learned that parts of the equipment my lab uses were actually designed by the graduate students and professors themselves, so not everything is streamlined as well as it should be, and they are sort of experimenting with the design at the same time as they are performing the actual experiments.

My daily schedule is pretty simple, and consists of my coming into lab around ten in the morning and doing some reading until lunch. After lunch I help out with experiments and analyses, and then I finish up till six with some more reading. If need be, I sometimes come into the lab after eight to finish up some experiments and such. The environment is very relaxed, and the whole lab is air-conditioned, which is great since Hong Kong is so very, very humid. All the graduate students are very friendly and know each other, and they go out to lunch together and stuff. Professor Xiao comes in once or twice a day to check up on everything and to give advice to the graduate students, but for the most part, they are on their own doing their own research.

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