Quinaldic Acid-Modified Perovskite Surface with Reduced Pinholes by Passivation Engineering for Improved Lifespan and Efficiency of Metal Halide Perovskite Solar Cells

Perovskite film surface passivation is a synergistic strategy for passivating traps and surface defects through the incorporation of heteroatom-containing functionalized organic molecules, aiming to improve the efficiency and longevity of perovskite solar cells. Typically, fullerene is a promising electron-transport material in hybrid inverted PSCs. However, some of the disadvantages of [6,6]-phenyl C61 butyric acid methyl ester (PCBM) exhibit unfavorable surface arrangement, low electron mobility, and easily developed recombination centers, all of which interfere with PSC performance. A small organic molecule quinaldic acid (QA) that contains a heteroatom (nitrogen) and a carboxyl functional group-based material has been employed as a passivation material on the perovskite surface at the perovskite/PCBM interface to enhance interface interactions and charge transport while decreasing defects and recombination centers. The surface passivation approach passivates defects and interacts with unreacted ions, improving solar performance as well as charge transfer and recombination resistance at the interface. As a result, the passivated device achieved a photovoltaic efficiency of 18.7%, with higher open-circuit voltage (Voc) and fill factor (FF) than pristine MAPbI3 at 16.5%. Stability testing revealed that the QA-treated device retained 90% of its power conversion efficiency (PCE) after 500 h, surpassing the untreated device, which retained 61% of its PCE. Most significantly, our findings establish a new criterion for investigating the QA molecule for high performance and stability in perovskite solar cells.