Importance of the Buffer Layer Properties for the Performance of Perovskite/Silicon Tandem Solar Cells

High Resolution Image Download MS PowerPoint Slide The power conversion efficiency of two-terminal perovskite/silicon tandem solar cells recently surpassed 30%, demonstrating the great potential of this technology. The most common electron-selective contact is a stack of a buckminsterfullerene film, a tin oxide buffer layer, and a transparent conductive oxide. While research is conducted on improving the fullerene/perovskite interface and on removing the buffer layer, less focus is put on tuning the buffer layer properties. In this work, the interplay of the doping densities in the fullerene film and the tin oxide layer as well as the impact of the tin oxide electron affinity on the device performance is investigated using electrical numerical simulations (technology computer-aided design). The simulated power conversion efficiency increases with higher doping densities in the fullerene film and the tin oxide layer, while an increasing conduction band offset between the two materials leads to a decreasing device performance. The results of this work imply that the properties of the buffer layer directly influence the performance of the tandem solar cell. In addition, the importance of measuring various material and interface characteristics in order to derive an improved device understanding is stressed.