Rational design of anion-doped perylene diimide-fullerene dimer as effective electron transporting material in inverted perovskite solar cells

Electron transport layer (ETL) plays a vital role in extracting and transporting electrons from perovskite active layer to the cathode in perovskite solar cells (PSCs). It is beneficial for boosting the efficiency and long-term stability of the devices. We skillfully incorporated fullerene and perylene diimide (PDI) and obtained a novel n-self-doping conducive C60-PDI-I dimer ETL. The introduction of C60 to PDI and the presence of intramolecular self-doping caused this hybrid molecule possessed high mobility and excellent defects passivation ability. As a result, C60-PDI-I dimers-based device demonstrated a significantly higher champion power conversion efficiency of 18.29% than the control device based on PCBM (15.60%) and PDI (14.38%). To the best of the authors' knowledge, this high PCE value is the leading level in the invert PSCs based PDI derivatives as ETLs. The overall mechanism analysis results showed that the origin enhancement of PCE was attributed to the improved electron extraction, reduced nonradiative recombination, and excellent defect passivation. Additionally, the long-term stability of devices based on C60-PDI-I dimers was significantly enhanced, owing to the strong hydrophobic properties of C60-PDI-I dimers. The successful application of C60-PDI hybrid dimmers provide a new insight for designing novel PDI-based electron transport materials.