Cyclization of Inner Linear Alkyl Chains in Fused‐Ring Electron Acceptors Toward Efficient Organic Solar Cells

Abstract

By changing the structures of the side chain on the backbone of the Y6 acceptor, many Y‐series acceptors have been synthesized to investigate the relationships between structures and properties of the fused‐ring electron acceptors (FREAs). However, not much attention has been paid to the effects of cycloalkane substituents on optoelectronic, morphological, and photovoltaic properties of the FREAs. Here, a brand‐new FREA D12 is developed by incorporating cyclohexylmethyl functional groups into the pyrrole rings of the backbone of the Y6 acceptor, and a similar compound E12 with the linear n‐heptane side chains is also synthesized for comparison. After the cyclization of the alkyl side‐chain, the molecular orientation of D12 exhibits favorable face‐on dominant, which endows D12 with higher charge mobility. Consequently, the organic solar cells (OSCs) with PM6 as donor and D12 as acceptor deliver the maximum power conversion efficiency of 17.3%, along with an excellent fill factor of 0.794, which is much higher than those of the PM6:E12‐based OSCs. The results reveal that introducing an inner cyclized alkyl chain on the pyrrole motif is a simple and feasible strategy to regulate molecular orientation and improve photovoltaic properties, which might provide guidelines for developing high‐performance electron acceptors.