Electron blocking enables solar cells with 18.5% efficiency

German and Swiss scientists have jointly developed a perovskite solar cell using carbon electrodes that is as high as 18.5% efficient and retains 82% after 500 hours of continuous light. Although the efficiency of this cell lags far behind other perovskite solar devices, it is produced using a low-temperature process throughout, making it possible to achieve low-cost, large-scale production, making this approach worthy of further exploration.

In a newly published paper, scientists led by the Fraunhofer Institute for Solar Energy Systems said: "[Currently commonly used] metal contact electrodes accelerate the degradation of perovskite solar cells due to the diffusion of metal impurities on the surface. Replacing metal contacts with chemically inert, robust carbon-graphite electrodes in perovskite solar cells—i.e., carbon-based perovskite solar cells (C-PSCs)—can fundamentally solve this problem. It has environmental pressure handling capabilities based on industrially mature printing technology, so it is quite promising for commercialization.”

They went on to explain that another problem occurred in C-PSC cells, resulting in a performance loss at the interface of the carbon electrode with the perovskite layer. To overcome this problem, the Fraunhofer Institute for Solar Energy Systems ISE, in collaboration with scientists at the Swiss Federal Institute of Technology Lausanne (EPFL), developed a barrier layer that can be placed between the two.

They deposited another perovskite structure on the battery's active layer and used various imaging techniques to determine that this additional layer could stop electrons from moving in the "wrong" direction and improve battery performance.

They explain this approach in "Using 2D Perovskites as Electron Blocking Layers in High Efficiency (18.5%) Perovskite Solar Cells Using Printable Low-Temperature Carbon Electrodes" recently published in Advanced Energy Materials . As the title suggests, the team made a cell with a high efficiency of 18.5% and maintained an efficiency of 82% after 500 hours of sunlight exposure. The control device without the barrier achieved an initial efficiency of 15.7%, but lost 63% of its efficiency after 200 hours of illumination.

"We believe that the use of 2D perovskites as electron blocking layers (EBLs) can help pave the way for the future efficient and long-term stable practice of developing all-printed C-PSCs," the team concluded.