Shamrock-shaped nonfullerene acceptors containing nonhalogenated end groups for high-voltage organic photovoltaics

Developing new material systems simultaneously possessing high open-circuit voltage (VOC) and power conversion efficiency (PCE) has consistently been a focal research. Recently, our group successfully obtained a novel A-DA'D-A type shamrock-shaped NFA via utlizing a large conjugated acenaphtho [1,2-b]quinoxaline imide (AQI) unit as central core (A ' unit) and fluorinated 1,1-dicyanomethylene-3-indanone (IC) as end groups, and the final molecule AQI4 exhibited a PCE of 18 % with a VOC of 0.95 V. To further extend the familly of shamrock-shaped NFAs and upgrade their photovoltaic properties, herein, another shamrock-shaped NFA containing nonhalogenated end group IC was synthesized and named as AQI1. The reasonable cooperation of AQI and IC could facilitate to obtain an upshifted LUMO energy level, resulting in a decreased energy loss in organic photovoltaics (OPVs). Using the classic p-type polymer PM6 and a benzotriazole-based linear polymer PE4 as donors, both devices can achieve high VOC of 1.06 V and 1.02 V respectively. Finally, PM6:AQI1 and PE4:AQI1 combinations realized PCEs of 11.3 % and 13.7 % respectively, suggesting that benzotriazole-based polymers might be better choice to blend with shamrock-shaped NFAs. These results indicate that shamrock-shaped NFAs with nonhalogenated end groups may be a feasible and potential design strategy to achieve low-cost and high-VOC OPVs.