Modulation on electrostatic potential to build a firm bridge at NiO /perovskite interface for efficient and stable perovskite solar cells

The NiOx/perovskite interface in NiOx-based inverted perovskite solar cells (PSCs) is one of the main issues that restrict device performance and long-term stability, as the unwanted interfacial defects and undesirable redox reactions cause severe interfacial non-radiative recombination and open-circuit voltage (Voc) loss. Herein, a series of self-assembled molecules (SAMs) are employed to bind, bridge, and stabilize the NiOx/perovskite interface by regulating the electrostatic potential. Based on systematically theoretical and experimental studies, 4-pyrazolecarboxylic acid (4-PCA) is proven as an efficient molecule to simultaneously passivate the NiOx and perovskite surface traps, release the interfacial tensile stress as well as quench the detrimental interface redox reactions, thus effectively suppressing the interfacial non-radiative recombination and enhancing the quality of perovskite crystals. Consequently, the PSCs with 4-PCA treatment exhibited an eminently increased Voc, leading to a significant increase in power conversion efficiency from 21.28% to 23.77%. Furthermore, the unencapsulated devices maintain 92.6% and 81.3% of their initial PCEs after storing in air with a relative humidity of 20%-30% for 1000 h and heating at 65 °C for 500 h in a N2-filled glovebox, respectively.