At the silicon PV/nPV conference in Lausanne in mid-March, researchers from Solliance introduced its latest achievement, a perovskite solar cell with 93% near infrared transparency. At the same event, ECN demonstrated that stacking this cell on top of a silicon cell with its metal wrap through heterojunction technology, could achieve a cell efficiency of 26.3% – more than 3% above the efficiency of the silicon cell alone.
“By optimizing the ITO (indium tin oxide) composition and deposition conditions as well as careful design of the anti-reflection coating (ARC), an extremely high transparency is achieved for the top electrode, despite the low temperature process window,” says Solliance researcher Dong Zhang.
By itself, the perovskite cell achieved 16.4% efficiency. Solliance now plans to work on scaling up the process and creating demonstration modules. “Scaling up from a laboratory scale to an industrial process is one major barrier for a successful implementation of a new promising development,” says Sjoerd Venstra, Program Manager for perovskite solar cells at Solliance. “Now that the device was proven with spin coated layers, we use pilot scale equipment provided by our industrial partners to scale it to a viable industrial production process.”
The cell created by Solliance was combined with a metal wrap through silicon heterojunction cell by ECN. This cell added 9.9% to the tandem efficiency. “This result shows how feasible it is to achieve significant efficiency gain even over high-end crystalline silicon technology and based on industrial process technology,” says Gianluca Coletti, Director of ECN’s Industry Research Program. “At ECN we are working to further optimize the bottom cells and the module integration to obtain higher conversion efficiency, reliability, and lower production cost to match the market requirements for tandem applications.”