Effect of the Device Architecture on the Performance of FA0.85MA0.15PbBr0.45I2.55 Planar Perovskite Solar Cells

Hybrid perovskite solar cells have attracted an unprecedented research attention due to their skyrocketing record power conversion efficiency (PCE), which now exceeds 23% in less than a decade from the initial PCE of 3.8%. Besides the excellent optoelectronic properties of the perovskite absorbers, the high efficiencies are also dependent on preparation methods and advanced device engineering. In this study, the role of the device architecture (planar n-i-p vs inverted p-i-n structure) and of the charge-selective interlayer on the photophysical properties of the perovskite absorber and device performance are explored. FA(0.85)MA(0.15)PbBr(0.45)I(2.55) (MA = methylammonium, FA = formamidinium) as the perovskite absorber and chloride-capped TiO2 colloidal nanocrystals (TiO2-Cl) and poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as close-to-the-substrate layers in the conventional and inverted structures are employed, respectively. Extremely different device performances are demonstrated by the two structures. The device where the active layer is deposited on TiO2-Cl displays a champion PCE of 19.9%, while the one using PEDOT:PSS gives about 15.1% efficiency. The photophysical and electrical investigations indicate that the TiO2-Cl/perovskite interface has lower number of traps, underlining the importance of interfaces for achieving highly performing perovskite solar cells.