“A Blessing in Disguise” in Self‐Assembled Molecules Tailoring for Passivation of Printed Carbon‐Based Perovskite Solar Cells

ABSTRACT Self‐assembled molecules (SAMs) have emerged as highly promising materials for interface engineering in perovskite solar cells, yet significant challenges remain in terms of the mechanisms of interfacial interactions within the devices. In this study, we synthesized BrPA‐CPA by introducing two bromine atoms at the electron‐donating end of the SAM molecule TPA‐CPA. As an additive for printable mesoscopic perovskite solar cells (p‐MPSCs), this modification, while reducing the surface electrostatic potential of the electron acceptor and weakening its interaction with Pb 2+ defects, unexpectedly enhanced the passivation effect due to the introduction of multiple passivation sites, a true “blessing in disguise.” In addition to this, BrPA‐CPA facilitates the oriented growth of perovskite crystals, minimizing defect formation and significantly suppressing non‐radiative recombination. The band bending at the interfaces between the perovskite and electron transport layer/carbon electrode promotes efficient charge transport across the interfaces. As a result, the power conversion efficiency (PCE) of p‐MPSCs increases from 16.01% to 17.17%. This work presents a novel, highly effective strategy for the design of SAM additives, leveraging the control of active sites and surface electrostatic potential, thereby offering a new pathway for optimizing perovskite solar cell performance.