p‐Type Doping of Poly(3‐hexylthiophene) with the Strong Lewis Acid Tris(pentafluorophenyl)borane

Abstract

State‐of‐the‐art p‐type doping of organic semiconductors is usually achieved by employing strong π‐electron acceptors, a prominent example being tetrafluorotetracyanoquinodimethane (F 4 TCNQ). Here, doping of the semiconducting model polymer poly(3‐hexylthiophene), P3HT, using the strong Lewis acid tris(pentafluorophenyl)borane (BCF) as a dopant, is investigated by admittance, conductivity, and electron paramagnetic resonance measurements. The electrical characteristics of BCF‐ and F 4 TCNQ‐doped P3HT layers are shown to be very similar in terms of the mobile hole density and the doping efficiency. Roughly 18% of the employed dopants create mobile holes in either F 4 TCNQ‐ or BCF‐doped P3HT, while the majority of doping‐induced holes remain strongly Coulomb‐bound to the dopant anions. Despite similar hole densities, conductivity and hole mobility are higher in BCF‐doped P3HT layers than in F 4 TCNQ‐doped samples. This and the good solubility in many organic solvents render BCF very useful for p‐type doping of organic semiconductors.