Extended Data Fig. 5: Schematic diagram of band alignment extracted from UPS results.
From: Homogenizing out-of-plane cation composition in perovskite solar cells
The band structures of different depths have been combined through manually aligning the Fermi energy level, due to there were not actual contact junction of different detection region. a-b, Schematics of quasi-type I band alignment caused by FA-Cs phase segregation. In a solar cell with (a) p-i-n stacks, holes undergo extra energy loss at bottom region when it diffuses within the perovskite film, leading to charge carriers (holes) accumulate at this region. Ultimately break the carrier extraction equilibrium. The same situation would arise for the electrons in solar cells with (b) n-i-p configuration. c-d, Resultant flatten band alignment by PSP introduction in a device with (c) p-i-n configuration and (d) n-i-p configuration.
