Gate-bias stress causes changes in the electrical stability of thin-film transistors (TFTs), and this can degrade the device performance. This research highlights the effects of environmental conditions on the electrical stability of pentacene TFTs in which cross-linked poly(4vinylphenol-co-methyl methacrylate) (PVP-co-PMMA) was utilized as a gate dielectric layer. Under negative gate-bias stress, the fabricated TFTs exposed to ambient air showed a positive threshold voltage shift, whereas the devices under vacuum exhibited a negative threshold voltage shift. Furthermore, consecutive on/off switching operation of pentacene TFTs under ambient air induced an increase in the on-state drain current. These results are explained through the interaction between water molecules and PVP-co-PMMA, which causes the accumulation of holes in the TFT channel region having higher conductance.

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We investigate the effects of environmental conditions on the electrical stability of spin-coated 5,11-bis(triethylsilylethynyl)anthradithiophene (TES-ADT) thin-film transistors (TFTs) in which crosslinked poly(4-vinylphenol-co-methyl methacrylate) (PVP-co-PMMA) was utilized as a gate insulator layer. Atomic force microscopy observations show molecular terraces with domain boundaries in the spin-coated TEST-ADT semiconductor film. The TFT performance was observed to be superior in the ambient air condition. Under negative gate-bias stress, the TES-ADT TFTs showed a positive threshold voltage shift in ambient air and a negative threshold voltage shift under vacuum. These results are explained through a chemical reaction between water molecules in air and unsubstituted hydroxyl groups in the cross-linked PVP-co-PMMA as well as a charge-trapping phenomenon at the domain boundaries in the spin-coated TES-ADT semiconductor.

2,8-Difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (dif-TES-ADT) is a small molecule organic semiconductor that has drawn much interest as an active channel in Organic Thin Film Transistors (OTFTs). In particular, the solubility of dif-TES-ADT in numerous solvents and amorphous polymers, its chemical stability, and its ease in processing make it a supreme candidate for high performance devices. This review summarizes the progress in material crystallization and the film formation approach, including the surface treatment of Source/Drain metal electrodes with various self-assembled monolayers (SAMs) and the works on vertical phase segregation derived from blending dif-TES-ADT with various polymers. Electrical and environmental stabilities in dif-TES-ADT-based OTFTs and their origins are summarized. Finally, a discussion on the emerging applications of dif-TES-ADT OTFTs is explored. We believe that the individual effort summarized in this work will shed light on optimizing the electrical performance of dif-TES-ADT-based transistors and reveal their potential qualities, which will be useful to their applications in next-generation high performance organic electronics.

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