Spectroscopic and electrical characterization of α,γ-bisdiphenylene-β-phenylallyl radical as an organic semiconductor

The semiconductor properties of the earliest known stable radical, α,γ-bisdiphenylene-β-phenylallyl radical (Koelsch radical, 1•) were assessed using spectroscopic and electrical techniques. This radical undergoes reversible redox processes, and it has low redox potentials. In addition, 1• possesses long wavelength absorption bands, owing to the existence of a singly-occupied molecular orbital whose energy level lies between those of the HOMO and LUMO. A spin-coated thin-film of 1• displays photocurrent and an electron mobility of 6.3 × 10−7 cm2 V−1 s−1 on a trially-fabricated organic field effect transistor.