Welcome to the Thin-Film Solar Cell Group!
We work on solar cells, which produce electricity directly from sunlight without any moving parts and without wearing out or consuming anything. Our goal is to develop the technology so far that solar cells can be employed for competitive large-scale production of "green" electricity in Sweden and beyond. We are working towards this goal on several fronts in parallel.
On this site you can find a description of the technology along with a synopsis of our various research projects. We have a list of publications as well as notice spaces for advertizing available master theses and vacant positions for postgraduate students. Besides our research, we contribute to a number of courses at both the undergraduate and postgraduate level.
Where We Work
If you want to visit us, we are located in the Ångström Laboratory at Uppsala University. When parking your bike on the laboratory's northern bicycle-parking lot, you can already catch a glimpse of our day-to-day research, taking place in the cleanroom on Ångström's ground floor. Feel free to wave at the people in blue and green overalls — they may be solar cell researchers!
Funding and Cooperations
Our largest research grant, "Ångström Thin Film Solar Center", is funded by the Swedish Energy Agency. We receive further funding from Vinnova, from the trust funds in memory of Carl Trygger and Göran Gustafsson, from SolElprogrammet and from the initiative STandUP for Energy. We have several commercial collaboration projects in which we explore industry-specific problems.
Fabrication of Thin-Film Solar Cells
Thin-film solar cells are steadily gaining ground against against their silicon-based relatives on the rapidly growing solar cell market. At present there are three major thin-film technologies to be found on the market, each named after the material used for absorbing sunlight: Thin-film silicon (TF-Si), cadmium telluride (CdTe), and copper indium gallium diselenide (CIGS). Many more technologies exist still at the pre-commercial or research stage. One of these technologies is based on copper, zinc, tin and sulfur and/or selenium (CZTS) and seems to share many properties with CIGS. The advantage of this material over CIGS is that the rare elements indium and gallium are replaced by zinc and tin, which are found in larger amounts in Earth's crust.
Our projects comprise research into both CIGS and CZTS, as well as into all the other thin-film materials (back contact, buffer layer and front contact) that are needed for a complete solar cell. As CZTS is still a relatively new material for solar-cell applications, we believe that a lot of research remains to be done before the best components are found. The search for optimal material combinations is also a major theme of our CIGS-related research. Particular attention is given to the so-called buffer layer: together with the material quality of the CIGS absorber, the interface between CIGS and the buffer is by far the most important factor in achieving a highly efficient solar cell.
Evaluation of Thin-Film Solar Cells
Once solar cells are fabricated, it is equally important to measure them, to understand how they work and how they can be improved. For that reason, we have a measurement laboratory with electrical instruments and powerful lamps that are calibrated to be equivalent to full sunlight. The analyses done there are used on the one hand as direct feedback for the practical experiments in the cleanroom, and on the other hand as input data for computer models which allow a more detailed study of the functional principles of the solar cells.
The Ångström Laboratory is one Sweden's best-equipped laboratories for material characterization. We benefit greatly from these capabilities, for in order to study our materials we need both high-resolution microscopes and surface-sensitive analysis methods. The combined thickness of the active layers in a thin-film solar cell is around 3 micrometers — a twentieth of the diameter of a hair!