Phase-stable wide-bandgap perovskites enabled by suppressed ion migration

Wide-bandgap (> 1.7 eV) perovskites suffer from severe light-induced phase segregation due to high bromine content, causing irreversible damage to device stability. However, the strategies of suppressing photoinduced phase segregation and related mechanisms have not been fully disclosed. Here, we report a new passivation agent 4-aminotetrahydrothiopyran hydrochloride (4-ATpHCl) with multifunctional groups for the interface treatment of a 1.77-eV wide-bandgap perovskite film. 4-ATpH+ impeded halogen ion migration by anchoring on the perovskite surface, leading to the inhibition of phase segregation and thus the passivation of defects, which is ascribed to the interaction of 4-ATpH+ with perovskite and the formation of low-dimensional perovskites. Finally, the champion device achieved an efficiency of 19.32% with an open-circuit voltage (VOC) of 1.314 V and a fill factor of 83.32%. Moreover, 4-ATpHCl modified device exhibited significant improved stability as compared with control one. The target device maintained 80% of its initial efficiency after 519 h of maximum power output (MPP) tracking under 1 sun illumination, however, the control device showed a rapid decrease in efficiency after 267 h. Finally, an efficiency of 27.38% of 4-terminal all-perovskite tandem solar cells was achieved by mechanically stacking this wide-bandgap top subcell with a 1.25-eV low-bandgap perovskite bottom subcell.