Anchorable Perylene Diimides as Chemically Inert Electron Transport Layer for Efficient and Stable Perovskite Solar Cells with High Reproducibility

Oxide semiconductors like TiO2 and SnO2 are exclusively used to construct electron transport layer (ETL) in n-i-p-structured perovskite solar cells (PSCs). Despite high electron mobility and suitable energy levels, their complicated surface chemistry is detrimental to the interfacial stability as well as fabrication reproducibility. Alternatively, organic n-type semiconductors address these issues due to their defined molecular structures. Herein, the novel use of anchorable perylene diimides (PDI) and naphthalene diimide (NDI) as chemically inert ETLs is proposed to improve the stability and reproducibility of n-i-p-structured PSCs. Compared with NDI, the PDI analogues show more suitable lowest unoccupied molecular orbital (LUMO) energy levels (-4.1 vs. -3.8 eV) for matching the conduction band edge of metal halide perovskites, thus favoring the interfacial electron collection. The anchoring chains decorated on PDI entity are found to affect not only the solution processability of ETLs, but also the crystal quality of perovskites. More importantly, the interfacial perovskite decomposition is suppressed in such organic ETLs-based PSCs. These merits of the anchorable PDI-based ETLs enable approximate to 19% efficiency devices with excellent reproducibility and long-term stability, which outperform traditional TiO2-based n-i-p PSCs.