Enhanced Charge Collection in Non-Fullerene Organic Solar Cells Using Iridium Complex as an Electron Extraction Layer

Ultrathin iridium (Ir) complexes (e.g., bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic)) are first introduced as electron extraction layers (EELs) in non-fullerene organic photovoltaics (OPVs), and a set of devices based on non-fullerene materials is fabricated. It is demonstrated that this approach can rationally enhance the corresponding short current density and open circuit voltage and finally improve the photovoltaic performance of OPVs. Furthermore, optimized bilayer EELs using combined FIrpic and 8-hydroxyquinoline lithium (Liq) are investigated. The resulting device presents excellent power conversion efficiency (PCE) of 15.85%, which is much higher than that of control device without FIrpic layer (14.6%). Moreover, Ir complexes show great universality when combined with other materials serving as EELs. This may provide an extra direction for further enhancement of OPVs performance.

Automated summary

The use of ultrathin iridium complexes as electron extraction layers has been shown to improve the performance of non-fullerene organic photovoltaic devices, with optimized bilayer EELs achieving significantly higher power conversion efficiency. The universality of iridium complexes when combined with other materials as EELs may offer a promising direction for further enhancing the performance of OPVs.