Figure 6. a) Device schematic of PSCs with MAPb 0.5 Sn 0.5 I 3 absorber and fullerene derivatives as ETL. b) Energy diagram of various device layers, drawn relative to vacuum level set to zero by definition. c) J-V characteristics of devices under AM 1.5G simulated solar irradiation of 100 W m −2 with a fixed scan rate of 50 mV s −1 (no stabilization done prior to measurement). d) IPCE (EQE) spectra for devices. e)Molecular structures of the fullerene derivatives employed as ETL. Reproduced with permission. [19]