Trap Kinetics in Solution-Processed Organic Thin-Film Transistors

The role of traps in controlling source-drain current in organic thin-film transistors (OTFTs) is not well understood and has so far been studied only in structures with silicon dioxide as the dielectric. We study trap kinetics in solution-processed OTFT with a polymer gate dielectric and 6,13-bis(triisopropylsilylethynyl) pentacene as the organic semiconductor. The trapping kinetics has been studied at different temperatures using time analyzed transient spectroscopy, which enables the detailed line shape analysis of electrical transients. We show unambiguously that the non-exponential turn-ON current transients are not due to the capture of majority holes, but rather are due to the emission of electrons modulating the channel carrier concentration through field. Two dominant electron traps with the activation energies of 0.14 and 0.20 eV are identified of which the former is discrete and the latter continuously distributed.