Phenyl substitution in tetracene: a promising strategy to boost charge mobility in thin film transistors

Tetracene, one of the polyacene derivatives, shows eminent optical and electronic properties with relatively high stability. To take advantage of the intrinsic properties of the tetracene molecule and explore new semiconductors, herein, we report the design and synthesis of two novel p-channel tetracene derivatives, 2-(4-dodecyl-phenyl)-tetracene (C12-Ph-TET) and 2-phenyl-tetracene (Ph-TET). Top contact OTFTs were fabricated using these two materials as semiconductor layers, with charge mobilities up to 1.80 cm2 V−1 s−1 and 1.08 cm2 V−1 s−1, respectively. Our molecular modeling results indicate that the introduction of phenyl into tetracene can improve the efficient charge transport in electronic devices as a result of the increased electronic coupling between the two neighboring planes of the molecules. AFM images of the thermally evaporated thin films of these two materials show large grains, which correspond to the high mobilities of these devices. Consequently, the mobility of our OTFTs based on C12-Ph-TET is the highest for OTFTs based on tetracene derivatives reported to date. The single crystal analyses show the existence of π–π stacking interactions within the molecules with the introduction of mono-phenyl substituents, which is the main cause of the increased mobility. The impressive properties of these two materials indicate that the introduction of alkyl-phenyl and phenyl group could be an excellent method to improve the properties of the organic semiconductor materials.