Buried Interface Passivation with 3,4,5-Trifluorophenylboronic Acid Enables Efficient and Stable Inverted Perovskite Solar Cells

The p-i-n type perovskite solar cells with a nickel oxide (NiOx) hole transport layer in combination with self-assembled monolayers (SAMs) have a high power conversion efficiency (PCE) of over 26%. The surface properties of the SAM layer have a significant impact on the growth and crystallization of the perovskite film. In the meanwhile, defects formed during thermal annealing at the SAM layer and the perovskite layer interface would act as charge recombination centers, decreasing device performance and stability. To address these issues, this work introduces 3,4,5-trifluorophenylboronic acid (3,4,5-3FPBA) as the interfacial modification layer to improve the buried interface properties that enable better crystallization of the perovskite film. With the 3,4,5-3FPBA layer, based on the perovskite composition Cs_0.05(FA_0.98MA_0.02)_0.95Pb(I_0.95Br_0.05)₃, the device efficiency increased from 21.99% to 24.02%. A similar improvement was observed for the perovskite composition Cs_0.05FA_0.82MA_0.13Pb(I_0.85Br_0.15)₃, where the device efficiency increased from 21.87% to 22.76%. The universality of interface modification has been confirmed. In addition, based on the perovskite composition Cs_0.05FA_0.82MA_0.13Pb(I_0.85Br_0.15)₃, the resulting cells showed improved thermal stability, maintaining 75% of its initial efficiency after 500 h of continuous heating at 85 °C for unencapsulated devices.