Abstract
Interfacial recombination and ion migration between perovskite and electron-transporting materials have been the persisting challenges in further improving the efficiency and stability of perovskite solar cells (PVSCs). Here, we design a series of molecularly tailorable clusters as an interlayer that can simultaneously enhance the interaction with C(60) and perovskite. These clusters have precisely controlled structures, decent charge carrier mobility, considerable solubility, suitable energy levels, and functional ligands, which can help passivate perovskite surface defects, form a uniform capping net to immobilize C(60), and build a robust coupling between perovskite and C(60). The target inverted PVSCs achieve an impressive power conversion efficiency (PCE) of 25.6% without the need for additional surface passivation. Crucially, the unencapsulated device displays excellent stability under light, heat, and bias, maintaining 98% of its initial PCE after 1500 hours of maximum power point tracking. These results show great promise in the development of advanced interfacial materials for highly efficient perovskite photovoltaics.