An Ambipolar Alkynylborane Compound with Nearly Trap-Free Charge-Carrier Transport under Ambient Air Conditions

Owing to the influence of O 2 and H 2 O, ambipolar organic semiconductors with efficient charge-carrier transport and a wide HOMO–LUMO gap (>2.5 eV) in air are difficult to develop. To address this challenge, we report the synthesis and properties of a unique alkynylborane (R 2 B–C≡C−) compound, 1A10Ph, which bears a phenyl group at the 10-position of the anthracene in dimesitylborylethynylanthracene. This compound was stable in air and easily synthesized. Remarkably, the amorphous 1A10Ph sample exhibited nearly trap-free ambipolar nature with high hole and electron mobilities (∼10 –4 and ∼10 –3 cm 2 /(V s), respectively) under ambient air conditions, despite its shallow LUMO level (−3.0 eV) and wide HOMO–LUMO gap (2.6 eV). In particular, its electron mobility (4.0 × 10 –3 cm 2 /(V s)) at low electric field strength (0.1 MV/cm) is high for an amorphous small-molecule material. These results demonstrate the great potential of this molecular design as an exceptional ambipolar material with a wide bandgap.