A metal chelation strategy suppressing chemical reduction between PEDOT and polyethylenimine for a printable low-work function electrode in organic solar cells

摘要

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) with high electrical conductivity and optical transmittance is regarded as a promising printable transparent electrode for organic solar cells. Intrinsically, it has a high work function because PEDOT is in an oxidized state. The oxidized state is prone to chemical reduction by polyethylenimine (PEI) or ethoxylated PEI (PEIE) or sol-gel ZnO precursors (ethanolamine contained) during work function tuning. In this work, we report zinc-ion chelated PEIE (denoted as PEI-Zn) deposited on the PEDOT:PSS electrode to reduce its work function as an efficient electron-collecting electrode. The introduction of zinc ions can effectively suppress the chemical reduction of PEDOT:PSS films by PEIE. High optical transmittance and electrical conductivity of PEDOT:PSS remain during the coating. The PEI-Zn can be as thick as 70 nm on PEDOT:PSS as an interlayer. Devices were fabricated on the low-work function PEDOT:PSS/PEI-Zn electrode. With the active layer of PM6:Y6, the cell shows a power conversion efficiency of 11.2% (open-circuit voltage of 0.81 V, short-circuit current of 21.3 mA cm(-2), and fill factor of 0.65).