Noncovalently fused-ring electron acceptors with near-infrared absorption for high-performance organic solar cells

Hao Huang,Cuihong Li,Jinsheng Song,Wei Ma,Jinjin Yang,Xinjun Xu,Shiyu Feng,Wenyue Xue,Zheng Tang,Qingxin Guo,Zhishan Bo,Zhaozhao Bi,Cai’E Zhang

doi:10.1038/s41467-019-11001-6

Abstract

Non-fullerene fused-ring electron acceptors boost the power conversion efficiency of organic solar cells, but they suffer from high synthetic cost and low yield. Here, we show a series of low-cost noncovalently fused-ring electron acceptors, which consist of a ladder-like core locked by noncovalent sulfur–oxygen interactions and flanked by two dicyanoindanone electron-withdrawing groups. Compared with that of similar but unfused acceptor, the presence of ladder-like structure markedly broadens the absorption to the near-infrared region. In addition, the use of intramolecular noncovalent interactions avoids the tedious synthesis of covalently fused-ring structures and markedly lowers the synthetic cost. The optimized solar cells displayed an outstanding efficiency of 13.24%. More importantly, solar cells based on these acceptors demonstrate very low non-radiative energy losses. This research demonstrates that low-cost noncovalently fused-ring electron acceptors are promising to achieve high-efficiency organic solar cells.

Highlights

Non-fullerene fused-ring electron acceptors boost the power conversion efficiency of organic solar cells, but they suffer from high synthetic cost and low yield
In our previous work[17], we have developed a kind of noncovalently fused-ring electron acceptors (NC-Fused-ring electron acceptors (FREAs)), in which the intramolecular noncovalent interactions can lock the aromatic units to form a ladder-like structure
The S···O interactions, which have been used in developing highperformance organic semiconductors by Watson and colleagues[19,20,21], could endow the central donor core with a planar ladder-like structure. The structure of such NC-FREAs is somewhat similar to acceptors with nine covalently fused rings, but the synthesis of the former is much easier than that of the latter

Summary

Introduction

Non-fullerene fused-ring electron acceptors boost the power conversion efficiency of organic solar cells, but they suffer from high synthetic cost and low yield. This research demonstrates that low-cost noncovalently fused-ring electron acceptors are promising to achieve high-efficiency organic solar cells. The S···O interactions, which have been used in developing highperformance organic semiconductors by Watson and colleagues[19,20,21], could endow the central donor core with a planar ladder-like structure The structure of such NC-FREAs is somewhat similar to acceptors with nine covalently fused rings, but the synthesis of the former is much easier than that of the latter. The morphology of blend films is optimized by changing the central 2,5-bis(alkyloxy)phenylene unit to achieve high-efficiency OSCs. As expected, the four NC-FREAs display broad absorption bands ranging from 550 to 900 nm, whereas a similar acceptor molecule (DC6-IC) with a 2,5-dihexylphenylene unit instead of a 2,5-bis(alkyloxyphenylene) unit only absorbs light from 550 to 750 nm. The PCE is further improved to 13.24% for solar cell based on fluorinated acceptor DOC2C6-2F after thermal annealing at 100 °C for 5 min

Methods

Results

Conclusion