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, text{N}{prime } -bis(2-octyldodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl)-alt-5, 5{prime } -(2, 2{prime } -bithiophene)) (N2200) OFETs. The injection barrier, such as Schottky barrier, at the metal/semiconductor interface was effectively weakened with the In interlayers thickness ( {T}-{In} ) increasing from 0 to 6 nm. The mechanism of electron injection changed from thermionic emission to tunneling, as the {T}-{In} reaching 6 nm. It results in a marked improvement in electrical properties for N2200 OFETs. The mobility increased from 0.09 to 0.29 cm {}{2}cdot text{V}{-1}cdot text{s}{-1} while the subthreshold swing decreased from 2.7 to 0.8 text{V}cdot dec-1 with the {T}-{In}. This work provides an efficient approach for the electron injection improvement in n-type OFETs.