Innovative Design and Synthesis of Fullerene-Terpyridine Derivatives for Enhanced Electron Transport in Inverted Perovskite Solar Cells.

In this study, three fullerene derivatives─, , and ─were synthesized and investigated as additives in PCBM-based electron-transporting layers (ETLs) for inverted perovskite solar cells (PVSCs). The incorporation of and into the ETLs led to improved ETL morphology and passivation of crystal defects on the surface of the methylammonium lead iodide (MAPbI) layer. This defect passivation enhanced crystal quality, increased UV-vis absorption, reduced charge recombination, and improved electron mobility in the - and -based PVSCs. The passivation effect of , which contains a 2,2':6',2″-terpyridine (TPY) unit, was found to be superior to that of , which features a -butyl ester group. As a result, PVSCs utilizing exhibited enhanced photovoltaic performance compared to those incorporating . To further investigate the contribution of the TPY moiety to the passivation effect, was neutralized with HCl to afford . As anticipated, the protonation of the TPY group in resulted in poorer ETL morphology and diminished defect passivation within the MAPbI layer. Consequently, no improvement in photovoltaic properties was observed for PVSCs treated with . The architecture of the inverted PVSCs doped with fullerene derivatives consisted of indium tin oxide/NiO/MAPbI/fullerene derivative: PCBM/bathocuproine/Ag. Among the fullerene-based additives, demonstrated the highest photovoltaic performance, achieving a power conversion efficiency (PCE) of 20.10%, an open-circuit voltage of 1.07 V, a short-circuit current density of 24.85 mA cm, and a fill factor of 75.6%. Furthermore, the -based PVSC retained 80% of its initial PCE after 450 h of storage under ambient conditions (30 °C, 40% relative humidity).