To find an interlayer or complete replacement to the expensive C₆₀–the electron transport layer in perovskite solar cells, PEPPERONI partners investigated four compound groups for their suitability. During device testing, 9-(dicyanomethylene) fluorene and phosphine oxide derivatives showed the most promise to be a C₆₀ replacement. Priority will be given to improving charge mobility of the selected compound groups. Structures of 9-(dicyanomethylene)-fluorenes will be modified to ensure more orderly packing of the molecules and thus improving speed of charge hopping between molecules. To improve charge mobility in the phosphine oxide derivatives, electron accepting groups will be identified with additional screening of the suitable electron transporting chromophores.