Highly Soluble Perylene Diimide Polymer as Hydrophobic Interlayer toward High Stability Perovskite Solar Cell

Abstract Constructing functionalized interlayers in buried surface of perovskite solar cells (PSCs) is highly desirable but yet challenging due to the inevitable erosion of high‐polarity DMF (i.e., N,N ‐dimethylformamide) solvent during the solution processing of the perovskite layer. In this work, two novel perylene diimide‐octyl polyhedral oligomeric silsesquioxane (PDI‐OPOSS)‐based polymers are designed and synthesized via ring‐opening metathesis polymerization (ROMP), as stable and multifunctional interlayer in PSCs. The OPOSS units are attached to the side chain of the polynorbornene skeleton through a soft ( P1 ) or rigid ( P2 ) spacer. The introduction of the OPOSS units enhances the polymers’ solubility in low‐polarity organic solvents, resulting in excellent film‐forming ability and strong hydrophobicity. Meanwhile, the PDI groups tethered to the polynorbornene backbone provide an electron transport path, crucial for its application as an interlayer between the perovskite active layer and charge‐transport layer in PSCs. These newly developed PDI‐OPOSS polymers efficiently tailor energy level alignments of buried surface and enhance charge transport within PSCs, leading to an impressive efficiency of 23.06% achieved by the P2‐ modified PSC. This work provides new insights to significantly potential applications of semi‐conducting interlayer materials in perovskite photovoltaics.