This work reports on the fabrication of organic thin-film transistors ͑OTFTs͒ with a solution-based 6,13-bis͑triisopropylsilylethynyl͒pentacene by a drop-casting method, and the determination of the electrical properties of OTFTs having different source/drain interdigitated-finger electrodes. The results show that the hysteresis in transfer characteristics of the OTFTs depends on the variation of contact fingers. These hystereses lead to changes in threshold voltage, which originates from charge trapping/detrapping at or near the organic semiconductor/dielectric interface. These related phenomena also influence the device parameters such as the field-effect mobility, the on/off current ratio, and the gate current.Organic thin-film transistors ͑OTFTs͒ are now being widely investigated due to their potential advantages including easy processing, simple structure, and low process temperature, all of which provide good compatibility with plastic substrates. Recently many research groups have successfully demonstrated numerous OTFTdriven devices, such as liquid-crystal displays, 1 organic lightemitting diodes, 2 and electronic papers. 3 These technologies have received considerable attention recently because solution processability enables a low cost fabrication process such as spin coating, 4 drop casting, 5 screen printing, 6 and spray coating 7 for large areas.The position aberration of the transistors or the variation in the source-drain geometries ͑channel width W or channel length L and source-drain electrode shapes defined by nonrectangular or rectangular types͒ significantly affects the pixel-driving properties of the transistors, which results in the deterioration of the display performances. Therefore, it is important for the channel geometry, where the channel is substantially under the pixel electrode, to be considered at the design stages.OTFTs can have channels defined by their source-drain interdigitated fingers ͑SDIFs͒ on the drain and pixel electrodes, giving a larger W/L if the OTFT resided only along one or more edges of the pixel. SDIF designs are advantageous because they allow for maintaining a larger W/L ratio with a larger L than for an OTFT constrained to only being able to lie adjacent to the pixel electrode. This permits the use of printing and other techniques, for fabricating display back-planes that are not capable of attaining the fineresolution limits of standard silicon processing using photolithography. Also, SDIF designs enable the achievement of larger W and L without reducing the aperture ratio of the display. 8