“Mutually Doped” Conjugated Polyelectrolyte‐Polyoxometalate Complex as Hole Transporting Material for Efficient Organic Solar Cells

Comprehensive Summary Compared to electron transporting layer materials, the species and numbers of hole transporting layer (HTL) materials for organic solar cells (OSCs) are rare. The development of HTL materials with excellent hole collection ability and non‐corrosive nature is a long‐standing issue in the field of OSCs. Herein, we designed and synthesized a series of conjugated polyelectrolytes (CPEs) with continuously varied energy levels toward HTL materials for efficient OSCs. Through a “mutual doping” treatment, we obtained a CPE composite PCT‐F:POM with a WF of 5.48 eV and a conductivity of 1.56 х 10–3 S/m, meaning that a good hole collection ability can be expected for PCT‐F:POM. The OSC modified by PCT‐F:POM showed a high PCE of 18.0%, which was superior to the reference device with PEDOT:PSS. Moreover, the PCT‐F:POM‐based OSC could maintain 91% of the initial PCE value after storage of 20 d, meaning that the long‐term stability of OSCs is improved by incorporating the PCT‐F:POM HTL. In addition, PCT‐F:POM possesses good compatibility with large‐area processing technique; i.e., a PCT‐F:POM HTL was processed by the blade‐coating method for fabricating 1 cm2 OSC, and a PCE of 15.1% could be achieved. The results suggest the promising perspective of PCT‐F:POM in practical applications. The "mutual doping" effect led to a simultaneous increase in WF and conductivity. The PCT‐F:POM HTL was easily processed using the blade‐coating method for the fabrication of 1 cm–2 OSC, resulting in an achieved PCE of 15.1%.