Atomic Contact Enables Highly Oriented and Covered Self-Assembled Monolayers for Composite Hole-Selective Structure Achieving Efficient Perovskite Solar Cells

The coverage, orientation, and uniformity of the self-assembled monolayers (SAMs) are critical to fabricate efficient and stable p-i-n structured perovskite solar cells (PSCs), which are still greatly challenged by the uncontrollable growth and aggregation on varied substrates. Herein, we introduce three atomic layers of thick aluminum oxide on conductive substrates to provide contact with dense and uniform hydroxy sites for SAM molecules to grow on. As a result, the atomic contact enables highly oriented SAMs with higher coverage, which notably enhances the photon-generated hole-selective efficiency and efficiently eliminates the charge leakage. The orientation of the SAMs with the conjugated backbone parallel to the substrate makes for more efficient hole transport for the perovskite buried interface. To fill the gaps between the SAMs and the perovskite buried interface, an ultrathin poly(methyl methacrylate) (PMMA) layer is employed, which is helpful to block carrier recombination as well. The atomic contact-based composite hole-selective structure enables the p-i-n structured PSCs (0.09 cm2) and mini-module (aperture area of 14.40 cm2) achieving efficiency of 26.63% and 22.97%, respectively. The optimized devices retain 92.65% of the initial efficiency after 912 h under the ISOS-L-2 protocol and 97.33% efficiency for 2016 h under the ISOS-D-1 condition.