n-Type Oxazine-Fused Higher-Acene Analogues With High Stability and High Charge Mobility

Acenes are a fascinating class of molecules. And higher-acenes (>7 rings) with big beautiful structures are more likely to be continuously pursued. However, the instability, poor solubility, and challenging synthesis of higher-acenes significantly hinder their fundamental investigation. Of greater concern is that no stable n-type higher-acene analogues have been obtained to date. Here, using oxazine and benzene units as the building blocks, a novel series of higher-acene analogues (9 rings) named pentaphenotetraoxazines (PPTOs), is synthesized by chemical solution method. These compounds exhibit high solubility in common organic solvents, high stability under ambient conditions, deep lowest unoccupied molecular orbital levels below -4.1 eV, strong NIR absorbance, and narrow optical bandgap (<1.4 eV). In solution-processed organic field-effect transistors (OFETs), the devices demonstrate electron mobilities exceeding 0.1 cm² V^-1 s^-1, which are two and three orders of magnitude higher than those of prior reported higher-acene analogues and the homologous 5-ring derivative-triphenodioxazine (TPDO), respectively. Moreover, these n-type OFETs demonstrate excellent stability under ambient conditions without encapsulation. These results highlight the high stability and outstanding n-type semiconductor performance of oxazine-fused higher-acene analogues and demonstrate the potential of this strategy to develop even larger acene systems.