Bifunctional ionic liquid for enhancing efficiency and stability of carbon counter electrode-based MAPbI3 perovskites solar cells

[Display omitted] •Acetate ion functionalized polar ionic liquid (IL), 1-allyl-3-methylimidazolium acetate (AMIMOAc), has firstly been used not only as an additive in MAPbI3 perovskite film but also as an interfacial modification layer between SnO2 and MAPbI3 in carbon counter electrode-based perovskite solar cells.•The appropriate content of IL can reduce the number of trap states in MAPbI3 perovskite film to inhibit non-radiative recombination and increase carrier lifetime, further improve the PCE to 15.16%.•The stability of the devices has been improved remarkably. The device with AMIMOAc IL has retained 93% of its initial PCE after storing for 500 h. The potential of perovskite solar cells as a representative alternative to silicon-based solar cells has become significant owing to their unparalleled advancement in efficiency. However, the intrinsic instability of perovskite still hinders their large-scale commercial application, particularly of the decomposition of perovskite during device operation. To address this issue, an acetate-ion-functionalized polar ionic liquid, 1-allyl-3-methylimidazolium acetate (AMIMOAc), is used as an additive in MAPbI3 film. FTIR spectroscopy measurements show that AMIMOAc can anchor the organic cations via hydrogen bonding and enhance the Pb–O interaction in modified MAPbI3, leading to a continuous and dense morphology to increase the stability of MAPbI3. After optimizing the concentration of AMIMOAc, an additional interfacial modification layer accelerates the electron extraction and transport. By the synergy of both additive engineering and interface modification, the device not only achieves a high efficiency of 15.16%, but also maintains 93% of the initial PCE after 500 h, showing significantly improved stability. These results pave the way to a new strategy to improve efficiency and long-term stability of carbon counter electrode-based PSCs.