Advanced Organic Transistor-Based Sensors Utilizing a Solvatochromic Medium with Twisted Intramolecular Charge-Transfer Behavior and Its Application to Ammonia Gas Detection.

Here, we designed and developed an organic field-effect transistor (OFET)-based gas sensor by applying solvatochromic dye (Nile red, NR) with twisted intramolecular charge-transfer (TICT) behavior depending on the polarity of the surrounding molecules, as an auxiliary NR sensing medium (aNR-SM). As a polar molecule approaches, intra-charge transfers from the donor diethylamine group to the ketone group occur in the NR molecule, resulting in the twisting of the donor functional group and thereby increasing its dipole moment. Using this characteristic, NR was applied as an auxiliary sensing medium to the OFET for detecting ammonia (NH), a representative toxic gas.

Understanding adsorption geometry of organometallic molecules on graphite.

To comprehensively investigate the adsorption geometries of organometallic molecules on graphene, CpRu fragments as an organometallic molecule is bound on highly oriented pyrolytic graphite and imaged at atomic resolution using scanning tunneling microscopy (STM) (Cp = pentamethylcyclopentadienyl). Atomic resolution imaging through STM shows that the CpRu fragments are localized above the hollow position of the hexagonal structure, and that the first graphene layer adsorbed with the fragments on the graphite redeveloped morphologically to minimize its geometric energy. For a better understanding of the adsorption site and molecular geometry, experimental results are compared with computed calculations for the graphene surface with CpRu fragments.

Omnidirectionally Stretchable Organic Transistors for Use in Wearable Electronics: Ensuring Overall Stretchability by Applying Nonstretchable Wrinkled Components.

With the emergence of wearable human interface technologies, new applications based on stretchable electronics, such as skin-attached sensors or wearable displays, must be developed. Difficulties associated with developing electronic components with the high stretchabilities required for such applications have restricted the range of appearance and utilization of cost- or process-efficient stretchable electronics. Herein, we present omnidirectionally stretchable wrinkled transistors having a shape that replicates human skin, which operates stably on deformable objects or complex surfaces.

Precise Control over Polymer Semiconducting Films by Tuning the Thermal Behavior of the Thin-Film State's Crystalline and Morphological Structures.

The crystalline and morphological structures of polymer semiconducting films were controlled by selecting appropriate thermal properties of the polymeric chains, thereby improving polymer field-effect transistor (FET) performances. Poly(dioctyl-quaterthiophene-dioctyl-bithiazole) (PDQDB), comprising 5,5'-bithiazole and oligothiophene rings, was used as the basis for the polymer semiconductor studies. The and values of the thin-film state, rather than those of the bulk polymer state, were important in this study.

Engineering Asymmetric Charge Injection/Extraction to Optimize Organic Transistor Performances.

The introduction of an appropriate functionality on the electrode/active layer interface has been found to be an efficient methodology to enhance the electrical performances of organic field-effect transistors (OFETs). Herein, we efficiently optimized the charge injection/extraction characteristics of source/drain (S/D) electrodes by applying an asymmetric functionalization at each individual electrode/organic semiconductor (OSC) interface. To further clarify the functionalizing effects of the electrode/OSC interface, we systematically designed five different OFETs: one with pristine S/D electrodes (denoted as pristine S/D) and the remaining ones made by symmetrically or asymmetrically functionalizing the S/D electrodes with up to two different self-assembled monolayers (SAMs) based on thiolated molecules, the strongly electron-donating thiophenol (TP) and electron-withdrawing 2,3,4,5-pentafluorobenzenethiol (PFBT).