Surfactant-Encapsulated Polyoxometalate Complex as a Cathode Interlayer for Nonfullerene Polymer Solar Cells

Abstract

An alcohol-soluble, environmentally friendly, and low-cost surfactant-encapsulated polyoxometalate complex [(C8H17)4N]4[SiW12O40] (TOASiW12) as a cathode interlayer (CIL) has exhibited excellent universality for various active layers and cathodes in nonfullerene polymer solar cells (NF-PSCs). In particular, incorporating TOASiW12 as the CIL enhanced power conversion efficiencies (PCEs) of the PM6:Y6- based NF-PSCs with Al or Ag cathode to 16.14% and 15.89%, respectively, and the PCEs of PM6:BTP-BO- 4Cl-based NF-PSCs with Al or Ag cathode to 17.04% and 17.00%, respectively. More importantly, the performances of the devices with TOASiW12 were insensitive to the TOASiW12 thickness from 3 to 33 nm. Furthermore, the NF-PSCs with TOASiW12 exhibited better device stability. Combined characterization of the photocurrent density versus effective voltage, capacitance versus voltage and electron mobility demonstrated that TOASiW12 as the CIL effectively promoted exciton dissociation, charge-carrier extraction, built-in potential, charge-carrier density, and electron mobility in the NF-PSCs. These findings suggest that TOASiW12 is a promising, competitive CIL for NF-PSCs fabricated by roll-to-roll processing.