Synthesis, Characterization, and Charge-Transport Properties of Halogenated Dibenzo[a,j]perylenes

In designing organic semiconductors for organic devices, halogenation is a very popular strategy for tuning the electronic properties and packing arrangement in the solid state. Herein, we report the synthesis and characterization of halogenated dibenzo[a,j]perylene (DBP) with triethylsilyl (TES)-ethynyl substituents at the 8- and 16-positions (TES-DBP). The resulting compounds are characterized by optical, electrochemical, crystallographic, and computational studies to clarify the effect of halogenation on the optoelectronic properties and charge-carrier transport. It is found that the halogen atoms, the degree of halogenation, and their positional locations can alter the electronic properties and crystal packing of the compounds. In contrast to fluorinated TES-DBP, the chlorinated counterpart has red-shifted maximum absorption and lower electron affinity owing to the electron delocalization between DBP core and the unoccupied 3d orbitals of Cl atom. Organic field-effect transistor measurements demonstrate that TES-2ClDBP shows a hole mobility of 0.25 cm2 V-1 s-1, which is higher than TES-2FDBP and TES-DBP. On the other hand, TES-4ClDBP exhibits ambipolar transport characteristics with electron and hole mobilities up to 0.02 and 0.07 cm2 V-1 s-1, respectively.