High Open‐Circuit Voltage Wide‐Bandgap Perovskite Solar Cell with Interface Dipole Layer

Abstract Wide‐bandgap perovskite solar cells (PSCs) with high open‐circuit voltage (V_oc) represent a compelling and emerging technological advancement in high‐performing perovskite‐based tandem solar cells. Interfacial engineering is an effective strategy to enhance V_oc in PSCs by tailoring the energy level alignments between the constituent layers. Herein, n‐type quinoxaline‐phosphine oxide‐based small molecules with strong dipole moments is designed and introduce them as effective cathode interfacial layers. Their strong dipole effect leads to appropriate energy level alignment by tuning the work function of the Ag electrode to form an ohmic contact and enhance the built‐in potential within the device, thereby improving charge‐carrier transport and mitigating charge recombination. The organic interfacial layer‐modified wide‐bandgap PSCs exhibit a high V_oc of 1.31 V (deficit of <0.44 V) and a power conversion efficiency (PCE) of 20.3%, significantly improved from the device without an interface dipole layer (V_oc of 1.26 V and PCE of 16.7%). Furthermore, the hydrophobic characteristics of the small molecules contribute to improved device stability, retaining 95% of the initial PCE after 500 h in ambient air.