π-Conjugated Dipolar Structures: Synergistic Dipole Superposition for Cathode Modification toward Ohmic Contact and Defect Passivation in Solar Cells

Cathode interfacial layers (CILs) are of paramount importance in eliminating the Schottky barrier and enhancing the built-in electric field of solar cells. A profound exploration of the novel design principles for CILs and a clear elucidation of their underlying working mechanisms are undeniably crucial for developing new CIL materials and improving the performance of related devices. In this study, we meticulously designed four dipole molecules featuring different anchoring groups and intramolecular dipole moments, with the aim of conducting an in-depth investigation into the design strategy of employing dipole molecules as cathode interfacial layers. By harnessing the synergistic effect of the intramolecular dipole and the dipole formed between the anchoring group and the metal electrode, Rh-Py can significantly increase the interfacial dipole moment. This not only effectively strengthens the built-in electric field but also optimizes the ohmic contact in organic solar cells, enabling the power conversion efficiency to surpass 20% successfully. Furthermore, the strong interaction between Rh-Py and Pb²⁺ enables it to effectively passivate Pb²⁺ defects in perovskite films. When utilized as an antisolvent additive in perovskite solar cells, Rh-Py can markedly reduce nonradiative energy losses and enhance the open-circuit voltage, thereby achieving an impressive PCE of up to 25.80%. Our research findings have shed light on the design principles of fully conjugated dipolar molecules as a new type of interfacial layer material and demonstrated their versatile application potential in the fields of organic and perovskite solar cells.