Stability issues could prevent lead halide perovskite solar cells (PSCs) from commercialization despite it having a comparable power conversion efficiency (PCE) to silicon solar cells. Overcoming drawbacks affecting their long‐term stability is gaining incremental importance. Excess lead iodide (PbI2) causes perovskite degradation, although it aids in crystal growth and defect passivation. Herein, we synthesized functionalized oxo‐graphene nanosheets (Dec‐oxoG NSs) to effectively manage the excess PbI2. Dec‐oxoG NSs provide anchoring sites to bind the excess PbI2 and passivate perovskite grain boundaries, thereby reducing charge recombination loss and significantly boosting the extraction of free electrons. The inclusion of Dec‐oxoG NSs leads to a PCE of 23.7 % in inverted (p‐i‐n) PSCs. The devices retain 93.8 % of their initial efficiency after 1,000 hours of tracking at maximum power points under continuous one‐sun illumination and exhibit high stability under thermal and ambient conditions. Effectively managing excess lead iodide is crucial for enhancing perovskite stability. An innovative approach, tailoring functionalized oxo‐graphene nanosheets, stabilizes the perovskite structure and improves charge extraction. This leads to a significant boost in power conversion efficiency and long‐term stability in inverted (p‐i‐n) perovskite solar cells, providing a novel perspective on stabilizing photovoltaic devices.