Introducing alkoxy groups as outer side chains and substituents of π-bridges obtains high-performance medium-bandgap polymerized small molecule acceptors

• Published in: Science China. Chemistry 2023-10, Vol.66 (10), p.2912-2920
• Main Authors: Gong, Yufei, Zou, Tianwei, Li, Xiaojun, Zhuo, Hongmei, Qin, Shucheng, Sun, Guangpei, Meng, Lei, Li, Yongfang
• Format: Article
• Language: English
• Subjects: Charge transfer; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Energy conversion efficiency; Energy gap; Open circuit voltage; Photovoltaic cells; Polymerization; Polymers; Short circuit currents; Solar cells; Synthesis
• ISSN: 1674-7291; 1869-1870
• DOI: 10.1007/s11426-023-1773-0

The medium-bandgap polymerized small molecule acceptors (PSMAs) have broad application scenarios. However, the effort in the molecular design of the high-performance medium-bandgap PSMAs is limited. In this article, we introduce alkoxy groups as outer side chains and as substituents of the thiophene π -bridges of the high-performance PSMA PY-IT to synthesize a medium-bandgap PSMA PO-TO. Due to that the non-covalent interaction between the alkoxy groups and the terminal groups of the small molecule acceptor (SMA) unit can weaken the intramolecular charge transfer (ICT) effect, the bandgap of PO-TO is enlarged and its absorption is blue-shifted compared with PY-IT, while the absorbance of PO-TO solution and film is enhanced significantly compare with that of PY-IT. When blended PO-TO with the polymer donor PBQx-TF, the corresponding all-polymer solar cells (all-PSCs) exhibit an open-circuit voltage ( V oc ) exceeding 1.04 V with a power conversion efficiency (PCE) of 13.75%. Furthermore, PO-TO was used as the third component to fabricate ternary all-PSCs with PBQx-TF as the polymer donor and PY-IT as the main polymer acceptor, and the ternary all-PSCs based on PBQx-TF:PY-IT:PO-TO (1:1:0.2, w/w/w ) demonstrated a high PCE of 17.71% with simultaneously improved V oc of 0.940 V, short-circuit current density ( J sc ) of 24.60 mA cm −2 and fill factor (FF) of 76.81%. In comparison, the binary all-PSCs based on PBQx-TF:PY-IT showed a PCE of 16.77%. This result indicates that introducing alkoxy groups is a promising strategy for synthesizing high-performance medium-bandgap PSMAs.