Researchers from HZB, Oxford University, Technical University Berlin and Oxford PV have shown that the infrared reflection losses in tandem cells processed on a flat silicon substrate (such as perovskite/silicon tandem cells) can be significantly reduced by using an optical interlayer, consisting of nanocrystalline silicon oxide. Based on this, the team managed to achieve impressive efficiency and reported that the best tandem device in this work reached a certified conversion efficiency of 25.2%.
Perovskite/silicon tandem solar cells are attractive for their potential for boosting cell efficiency beyond the crystalline silicon (Si) single-junction limit. However, the relatively large optical refractive index of Si, in comparison to that of transparent conducting oxides and perovskite absorber layers, often results in significant reflection losses at the internal junction between the cells in monolithic (two-terminal) devices. Therefore, light management is crucial for improving photocurrent absorption in the Si bottom cell.