Watching solar cells grow

Posted on June 28, 2013
The HZB scientists constructed a new kind of experimental chamber, which allows the analysis of polycrystalline chalcopyrite film formation during coevaporation when exposed to synchrotron light at BESSY I. Credit: Figure: R. Mainz/HZB

The HZB scientists constructed a new kind of experimental chamber, which allows the analysis of polycrystalline chalcopyrite film formation during coevaporation when exposed to synchrotron light at BESSY I. Credit: Figure: R. Mainz/HZB

For the first time, a team of researchers at the HZB led by Dr. Roland Mainz and Dr. Christian Kaufmann has managed to observe growth of high-efficiency chalcopyrite thin film solar cells in real time and to study the formation and degradation of defects that compromise efficiency.

 

To this end, the scientists set up a novel measuring chamber at the Berlin electron storage ring BESSY II, which allows them to combine several different kinds of measuring techniques. Their results show during which process stages the growth can be accelerated and when additional time is required to reduce defects. Their work has now been published online in Advanced Energy Materials.

Today’s chalcopyrite thin film cells based on copper indium gallium selenide are already reaching efficiencies of more than 20 percent. For the fabrication of the extremely thin polycrystalline layers, the process of coevaporation has lead to the best results so far: During coevaporation, two separate elements are evaporated simultaneously, first indium (or gallium) and selenium, then copper and selenium, and, finally, indium (or gallium) and selenium again. This way, a thin film of crystals forms, which exhibit only a small number of defects. “Until recently, we did not fully understand what exactly happens during this coevaporation process,” says Dr. Roland Mainz of the HZB’s Institute of Technology. The team of physicists worked for three years using on-site and real-time measurements to find an answer to this question.

Read more at: Phys.org