Fig. 1: Schematic of R2R-coated perovskite solar cells with carbon electrode.

The figure illustrates the design of NIP stack [tin oxide (SnO2)/ perovskite (MAPI)/HTL/Carbon] perovskite solar cells with various hole-transporting material candidates, including spiro-MeOTAD, PTAA, P3HT, and PEDOT.