A High‐Performance Dibenzothiophene‐Terminated Self‐Assembled Hole Transport Monolayer for Perovskite Solar Cells

Self‐assembled hole transport monolayers (SAMs) have become indispensable components of high‐performance inverted perovskite solar cells (PSCs). SAMs not only govern the interfacial hole extraction kinetics but also influence the crystallization quality of the overlying perovskite film and the properties of the buried interface. In this work, we designed and synthesized a novel SAM featuring a terminal dibenzothiophene group, designated DBT‐4PACz. Our investigation reveals that, compared with the commercial benchmark Me‐4PACz, DBT‐4PACz forms denser and more uniform coverage on the substrate, exhibits higher conductivity, and demonstrates a more favorable energy level alignment with the perovskite. Moreover, the thiophene moiety in DBT‐4PACz enhances the interaction with the perovskite. This, combined with the denser SAM layer, improves the crystallization quality of the perovskite and reduces interfacial defects. Leveraging this molecular design, inverted PSCs employing DBT‐4PACz achieved a remarkable power conversion efficiency of 27.01% (certified 26.62%), significantly surpassing the performance of Me‐4PACz‐based control devices (26.16%). Furthermore, DBT‐4PACz‐based devices exhibit superior operational stability.