Electron Injection Improvement of n-Type Organic Field-Effect Transistors With Indium Contact Interlayer

The organic field-effect transistors (OFETs) have developed rapidly in recent years. However, compared with the p-type OFETs, the n-type devices always show poorer performance due to their hard electron injection and low stability. It is necessary to further improve the charge injection properties of n-type OFETs. In this work, indium (In) layers, as an interlayer above contacts, were adopted for electron injection improvement in the n-type poly((N, N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl)-alt-5, 5'-(2, 2'-bithiophene)) (N2200) OFETs. The injection barrier, such as Schottky barrier, at the metal/semiconductor interface was effectively weakened with the In interlayers thickness ( TIn) increasing from 0 to 6 nm. The mechanism of electron injection changed from thermionic emission to tunneling, as the TInreaching 6 nm. It results in a marked improvement in electrical properties for N2200 OFETs. The mobility increased from 0.09 to 0.29 cm2·V-1·-1while the subthreshold swing decreased from 2.7 to 0.8 V·dec-1with the TIn. This work provides an efficient approach for the electron injection improvement in n-type OFETs.