High-Voltage Organic Thin-Film Transistors on Flexible and Curved Surfaces

A pentacene (C₂₂H₁₄)-based high-voltage organic thin-film transistor (HVOTFT) was demonstrated on both a rigid and a flexible substrate. The HVOTFT showed minimal degradation of the current-voltage (I-V) characteristics under flexure. Consistent with the previous reports on amorphous silicon (a-Si) TFTs, the offset drain/source structure enabled high-voltage operation, allowing for the HVOTFT to switch very large drain-to-source voltages (VDS > 300 V) with a relatively lower controlling voltage (0 V <; V_G <; 20 V). The HVOTFT was evaluated with three different gate insulators to assess how the dielectric constant and interface states influence device performance. Due to the high electric field generated in the device, the HVOTFT suffered from impeded charge injection into the gated semiconductor channel, similar to that reported in a-Si-based high-voltage TFTs, as well as from a nonsaturating I-V characteristic behavior similar to the short-channel effects found in FETs. A field plate was implemented to improve charge injection into the gated semiconductor channel. Output characteristics of the HVOTFT were numerically corrected to demonstrate that the device I-V can be modeled with the existing Si-based FET models.