Influence of the semi-conductor layer thickness on electrical performance of staggered n- and p-channel organic thin-film transistors

In this study, we report on the influence of the semi-conductor thickness on organic thin-film transistors (OTFTs). Devices are fabricated with a top gate/bottom contact geometry on plastic substrates. Both n-channel and p-channel OTFTs made, respectively, from a N,N-dialkylsubstituted-(1,7&1,6)-dicyanoperylene-3,4:9,10-bis(dicarboximide) derivative (Polyera ActivInk™ N1400) and from 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) are studied and compared. Impact of the active semiconducting layer thickness on both contact resistance and mobility are uncorrelated by the use of the transfer line method (TLM). When increasing the thickness of the semi-conductor, we find an increasing contact resistance and a decreasing channel mobility for both n- and p-channel OTFTs. The loss of mobility with increased thickness is attributed to a degradation of the interface between the semi-conductors and the dielectric, and is studied by atomic force microscope (AFM).