One of the issues of high performance organic thin-film transistors (OTFTs) is reducing of contact resistance between source/drain and organic material. For the bottom contact OTFT, insertion of a special material is one of the best ways to reduce this resistance. Ideally, the barrier height is determined by the Fermi-level of an organic semiconductor and work function of metal. However, an interfacial state due to the unevenness of organic/ metal interface and/or a band offset of vacuum level interfere with this carrier injection/ extraction exist.
In these backgrounds, the enhancement of the charge injection and field effect mobility by inserting a thin (5 nm) germanium oxide (GeO) interlayer between the Au electrode and pentacene layer in a top contact pentacene based OTFTs is studied. In comparison with the pentacene-based OTFT with only-Au electrode, a device performance has been considerably improved, which exhibits the highest field effect mobility of 0.96 cm2/Vs. The improvement was attributed to significant reduction of barrier height at Au/pentacene interfaces and smoothed surface of pentacene layer after inserting the thin GeO layer.
