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

Abstract

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.

Hole/Electron Transporting Materials for Nonfullerene Organic Solar Cells

“…For example, bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato) iridium(III) (FIrpic) is one of the most investigated blue phosphorescent material in the context of OLEDs. [26] Zhou et al combined FIrpic with 8-hydroxyquinoline lithium (Liq) and used them as the ETL. [26] The insertion of FIrpic facilitated the existence of interfacial dipole, provided more interfacial properties for exciton dissociation, charge extraction and ultimately enhanced the performance of PM6:Y6 based devices (15.75 %).…”

“…[26] Zhou et al combined FIrpic with 8-hydroxyquinoline lithium (Liq) and used them as the ETL. [26] The insertion of FIrpic facilitated the existence of interfacial dipole, provided more interfacial properties for exciton dissociation, charge extraction and ultimately enhanced the performance of PM6:Y6 based devices (15.75 %). N719 is a popular dye used for dye-sensitized solar cells (DSSCs), which can also be used as ETL for OSCs.…”

“…Similar to Alq 3 , iridium complexes have also been widely used in OLEDs. For example, bis[2‐(4,6‐difluorophenyl)pyridinato‐C2,N](picolinato) iridium(III) (FIrpic) is one of the most investigated blue phosphorescent material in the context of OLEDs [26] . Zhou et al.…”

Organic–inorganic hybrid cathode interlayer materials for efficient organic solar cells

“…126 It was reported that iridium (Ir) complexes could also be processed as CILs for regular OSCs, but the obtained PCE of 12.38% for the PM6:Y6 system was rather moderate. 127 Moreover, metallophthalocyanine and naphthalocyanine derivatives have also been designed to be used as CILs in OSCs with conventional structures. 128–130 These small molecules are alcohol soluble and processed on top of the photoactive layer, giving both high performance fullerene and non-fullerene OSCs.…”