C60 Thin Films in Perovskite Solar Cells: Efficient or Limiting Charge Transport Layer?

In this work, we identify the importance of C60 and compact-TiO2 (cTiO2) as electron transport layers on the device performance of coevaporated n–i–p perovskite solar cells. We found (1) a synergetic effect between both layers when extracting the charges and (2) that optimization of the C60 layer is essential for obtaining devices with enhanced device performance. In particular, we found that a C60 layer of an optimum thickness (<15 nm) enhances the charge extraction when employed in a coevaporated perovskite solar cell. With thicker C60 layers (>20 nm), an additional charge transport resistance is observed by impedance analysis, indicating that devices with nonoptimized C60 thickness could limit the fabrication of highly efficient perovskite solar cells.