Regulating the perovskite/C60 interface via a bifunctional interlayer for efficient inverted perovskite solar cells

•A dual-function interlayer was proposed for defect passivation and energy rearrangement.•The post-treatment strategy shows great universality and is efficient in various perovskite composition and fabrication methods.•Inverted perovskite solar cells achieved a champion device efficiency of 24.7% at the reverse scan and much-enhanced stability. Inverted perovskite solar cells are promising candidates in photovoltaic fields due to their low-temperature processing, simplified fabrication, and enhanced stability when compared with the conventional configuration. However, the significant non-radiative recombination losses and energy alignment mismatch at the perovskite/C60 interface limit the device's performance and long-term stability. To overcome this drawback, we introduced trifluoromethoxy-functionalized phenethylammonium iodide salts with high polarity between the perovskite and C60 electron transporting layer. This bifunctional interlayer not only effectively passivates the perovskite surface and interface but also reduces the minority carriers through the band rearrangement at this interface, thus significantly suppressing the deteriorating interfacial non-radiative recombination. The modified interlayer also facilitates electron extraction by reducing the offset between the perovskite and C60, contributing to an improved photocurrent and fill factor. The resultant inverted perovskite solar cell based on a Cs0.05FA0.85MA0.10Pb(I0.95Br0.05)3 composition reveals a power conversion efficiency of 24.7 % at the reverse scan and shows negligible efficiency loss after 600 h of maximum power point tracking under one-sun illumination. Overall, this feasible deposition of ammonium-based interlayer establishes a successful demonstration of efficient and stable inverted devices to accelerate the commercialization of perovskite photovoltaics.