Multidentate Fullerene Boosts the Thermal Stability of Perovskite Solar Cells

Abstract The currently poor thermal stability of perovskite solar cells (PSCs) can be attributed, to a large degree, to the desorption of interfacial ligands and the revival of defect states, e.g., popular phenylethyl ammonium-based ones. Herein, we rationally design a multidentate fullerene derivative, 3,5-bis(2',5'-dihydro-1'H-[60]fullereno[1',2':1,2]pyrrolidin-3-yl) dibenzoic acid (PF2C), which not only stabilizes phenylethyl ammonium bromide (PEABr) on perovskite surfaces through robust coordination and intermolecular interactions but also simultaneously enhances defect passivation and electron extraction at the interface. As a result, this strategy increased the optimal power conversion efficiency (PCE) of PSCs without predepositing any hole-transport layer from 25.13 to 26.65%, at the top levels reported. Strikingly, the encapsulated devices retain 98.7% of their initial PCE after 2100 h of MPP tracking under continuous illumination and maintain 95.8% under 85 °C thermal aging (ISOS-L-3) for 1800 h, far surpassing the control, which retains only 56.4% after 820 h.