Impacts of Channel Length and Type of Active Layer on Electrical Properties of Organic Thin-Film Transistors: Theoretical and Experimental Investigations

Abstract

The organic thin film transistors made of different polymers with various channel lengths were fabricated, characterized and modeled. Three types of polymers with different polydispersity (PDI) and molecular weight were applied as active layers. Optimizing OTFTs were achieved by two technological ways, namely the treatment of SiO2 by octadecyl trichlorosilane (OTS) (self-assembled monolayers (SAM)) in correlation with channel length variation. The effect of treatment of SiO2 by OTS (octadecyl trichlorosilane) on the output and transfer characteristics along with the electrical parameters were investigated. In addition, the effects of polydispersity (PDI) and molecular weight of organic semiconductor were accounted. The characteristics of transistors depended on the exposure to SiO2 by OTS, channel length, polydispersity (PDI) and molecular weight of polymers. The devices fabricated with treatment of SiO2 by OTS along with organic semiconductor, possessing high molecular weight has a channel length of 2.5 μm, which showed outstanding mobility of 10–2 cm2V –1s–1, current ratio Ion/Ioff = 2.5 × 106 and a low contact resistance of 4.8 × 10 5 Ω. An analytical model reproduced output electrical properties having characteristics of fabricated devices. The obtained results by the model were fairly agreed with those obtained experimentally for long and short channel devices.