Ultrathin, transparent and flexible solar cells
30 May, 2009 04:42 pm
Prof John Rogers and his colleagues from the University of Illinois developed a method to print ultrathin, semitransparent and flexible cells on plastic and cloth, opening up a broad range of applications in the solar sector. He answers Scitizen's questions.
We have etching methods, for Si and GaAs, that allow us to slice off of the near surface region of a wafer, ultrathin (i.e. between 2 and 20 microns is typical) layers that can be formed into micro solar cells. The etching chemistries are different for these two materials systems, but the conceptual strategies are the same.
To what extent is it going to extend the range of applications of photovoltaic solar cells?
The thin geometry represents an efficient way to use the materials and the supporting wafers (in the case of GaAs), thereby providing the potential for cost reductions. The small sizes of the cells make passive thermal dissipation much more effective compared to conventional, bulk cells. This aspect is particularly important for concentrator systems (e.g. GaAs), and it simplifies the design of the focusing optics. Also, the thin geometry imparts a degree of mechanically flexibility that can not only facilitate transport and installation of modules, but also open up new application opportunities. Finally, we can control the spacings between individual microcells in completed modules, thereby allowing us to define, at the assembly stage, a definable level of optical transparency that could be important for certain uses.
There are lots of research groups working on new solar technologies. One might separate them into those that are developing new materials (dominated by organics and polymers) and those that are developing new ways to use old materials. We fall into the second category.
Are you confident in the commercialization of ultrathin and flexible solar cells within the end of the year as the semiconductor company Semprius claims to do?
Yes, Semprius has working prototypes now, and will refine these systems and distribute them to key groups for field tests this year. They will not, however, be in a position to manufacture them at high volumes. That part will, hopefully, come into place next year. It is important to point out that Semprius is *not* making flexible modules. They are making microconcentrator GaAs systems, for which the substrate is glass.
Interview by Clementine Fullias
Professor John A. Rogers currently holds a primary appointment in the Department of Materials Science and Engineering at the University of Illinois. His research includes fundamental and applied aspects of nano and molecular scale fabrication as well as materials and patterning techniques for unusual format electronics and photonic systems.