Aldol Condensation-Polymerized n-Doped Conjugated Polyelectrolytes for High-Performance Nonfullerene Polymer Solar Cells

Doping provides an efficient strategy to control the electronic properties of organic semiconductors. However, compared with the widely reported p-type doping protocols, n-type doping of organic semiconductors still remains a challenge. Herein, a series of novel n-doped conjugated polyelectrolytes (CPEs) with high doping levels and conductivity are designed. These CPEs are synthesized via a facile, metal-free, and high-yield aldol condensation protocol from bis-isatin and bis-oxindole monomers. The designed CPEs possess a n-type electron-deficient and rigid conjugated backbone, resulting in easy charge delocalization, enhanced n-doping behaviors, and high conductivity. The evolution on the counterions of these CPEs further alters their n-doping behaviors, charge transporting properties, and work function tunability, etc. By using these CPEs as electron transport materials (ETMs) for nonfullerene polymer solar cells (NF-PSCs), high power conversion efficiencies (PCEs) over 16% can be achieved when PM6:Y6 is used as the active component. Moreover, these CPEs can enable efficient NF-PSCs even if their thicknesses are up to 60 nm, indicating the potential of these CPEs as thickness-insensitive ETMs for the fabrication of large-area NF-PSCs.

Automated summary

This study designed a series of novel n-doped conjugated polyelectrolytes with high doping levels and conductivity, synthesized from bis-isatin and bis-oxindole monomers. The evolution of counterions further alters their n-doping behaviors and work function tunability. Used as electron transport materials in nonfullerene polymer solar cells, they can achieve high power conversion efficiencies over 16%.