The Empa Laboratory for Thin Films and Photovoltaics, headed by Ayodhya N. Tiwari, has broken its own record. The researchers improved the efficiency of energy conversion in CIGS solar cells on flexible polymer substrate to 20.8%. This is 0.4% higher than the previous brand held by the same group. As the technology of choice, the scientists have opted for copper indium gallium diselenide (Cu(In,Ga)Se2) or CIGS, which enables the manufacture of flexible, lightweight solar cells on polymer foils.
The new record results from the combination of three major improvements, explains Romain Carron, head of CIGS research activity at Empa's laboratory. "First, we have carefully adjusted the chemical composition of the absorber layer to improve its electronic and optical properties. Then we developed new methods for alkali metal doping. Finally, we adapted the properties of the interface between the absorber and the buffer layer/front contact to improve the performance of the cell". According to Carron, the meticulous work of Shiro Nishiwaki was essential to improve the performance of the cells.
Flexible CIGS solar modules are already commercially available, particularly from the Empa spin-off Flisom, which was co-founded by Tiwari. "Such high efficiency as we have now achieved in our laboratory demonstrates the potential of the technology. Future developments by the research team will focus in particular on transferring the process developed from laboratory to industrial scale in order to increase the power generation and profitability of photovoltaic systems.
The technological achievements and scientific findings are described in the special issue "Excellence in Energy" of the journal "Advanced Energy Materials" (DOI: 10.1002/aenm.201900408).
More information: https://www.empa.ch/web/s604/cigs-record-2019