Improving the performance of organic thin-film transistor with a doped interlayer

Top contact organic thin-film transistors (TC OTFTs) based on pentacene are fabricated. For improving the contact characteristics between the organic semiconductor thin-film and gold electrodes, we doped the starburst molecular 4,4′,4″-tris{N,(3-methylpheny)-N-phenylamino}-triphenylamine) (m-MTDATA), which is an excellent hole injection material for the organic light-emitting devices (OLEDs), into the interlayer contact with the electrodes. Compared with conventional TC OTFT, the performances of the organic transistor with the doped interlayer are improved. The field-effect mobility increases from 0.16 to 0.51 cm2/V s, and threshold voltage downshifts from –11 to –2.8 V for the linear region. The on/off current ratio is more than 104 when the gate voltage varies from 0 to –20 V. We ascribe the improvements to the doped interlayer for which the contact resistance is reduced and the hole injection is enhanced.