Anode Engineering with pH-Neutral Conjugated Polyelectrolyte Enabling Over 19% Efficiency in Organic Solar Cells

Abstract

The lack of effective hole-transporting layers (HTLs) materials has become a significant bottleneck in the advancement of organic solar cells (OSCs). Particularly, to obtain sufficient doping properties, most HTLs have to be used by mixing with substantial amounts of acid, which causes serious corrosion problems. Herein, by optimizing molecular conformation, we designed and synthesized two conjugated polyelectrolytes (CPEs) that exhibited superior hole-transporting capability without involving acid addition. The PEP-BT features a planar conjugated backbone constructed from the nonfused segment, which leads to an enhanced doping effect and highly ordered molecular arrangement. and reduced π–π stacking from 4.13 to 3.85 Å. These contributed to the outstanding hole collection performance of polyoxometalate-doped PEP-BT:POM4 while maintaining a neutral pH. The binary OSC showed a photovoltaic efficiency of 19.16%, illustrating an unprecedented example that a CPE-based HTL can provide a photovoltaic efficiency exceeding 19% in OSCs. Moreover, as another evidence of high-performance HTL, the organic light-emitting diode incorporating PEP-BT:POM4 exhibited a superior luminous efficiency to the reference device, along with a decrease of 0.4 V for turn-on voltage. The results from this work demonstrate the great potential of CPEs as HTL materials.