A Novel Self-Assembled Hole-Transporting Monolayer with Extending Conjugation for Inverted Perovskite Solar Cells

The application of self-assembled monolayers (SAMs) as hole-transporting materials has greatly improved the performance of inverted perovskite solar cells. Structure engineering of SAMs has proven to be an effective approach to enhance device performance. In this work, a novel SAM featuring extended conjugation is designed and synthesized, designated E-CbzBT. Compared with CbzBT, E-CbzBT exhibits enhanced asymmetric and noncoplanar screw-shaped configuration, leading to uniform and tight packing on ITO. The uniform packing of E-CbzBT increases the wettability of the perovskite precursor solution on the substrate, thereby facilitating perovskite crystallinity and suppressing interfacial trap density more effectively than CbzBT. Accordingly, inverted PSCs employing E-CbzBT reach a champion power conversion efficiency of 25.15%, surpassing 24.06% for CbzBT-based devices. Importantly, the E-CbzBT-based PSCs demonstrate superior ambient and thermal stability. The extending conjugation approach in SAMs represents a promising avenue for further advancements in perovskite solar cell technology.