High-Resolution Inkjet-Printed Oxide Thin-Film Transistors with a Self-Aligned Fine Channel Bank Structure

A self-aligned inkjet printing process has been developed to construct small channel metal oxide (a-IGZO) thin-film transistors (TFTs) with independent bottom gates on transparent glass substrates. Poly­(methylsilsesquioxane) was used to pattern hydrophobic banks on the transparent substrate instead of commonly used self-assembled octadecyltrichlorosilane. Photolithographic exposure from backside using bottom-gate electrodes as mask formed hydrophilic channel areas for the TFTs. IGZO ink was selectively deposited by an inkjet printer in the hydrophilic channel region and confined by the hydrophobic bank structure, resulting in the precise deposition of semiconductor layers just above the gate electrodes. Inkjet-printed IGZO TFTs with independent gate electrodes of 10 μm width have been demonstrated, avoiding completely printed channel beyond the broad of the gate electrodes. The TFTs showed on/off ratios of 10⁸, maximum mobility of 3.3 cm² V^–1 s^–1, negligible hysteresis, and good uniformity. This method is conductive to minimizing the area of printed TFTs so as to the development of high-resolution printing displays

0.7% Roll-off for Solution-Processed Blue Phosphorescent OLEDs with a Novel Electron Transport Material

A novel cross-linkable electron transport material, 1,3,5-tris­(5-(4-vinylphenyl)­pyridin-3-yl)­benzene (TV-TmPY), for solution-processing as well as a small molecule, 1,3,5-tris­(5-phenylpyridin-3-yl)­benzene (TmPY), for vacuum deposition were designed and synthesized for OLEDs. TV-TmPY and TmPY with identical core structures are fully characterized to systematically investigate the impact of solution processing and vacuum deposition on the performance of phosphorescent OLEDs. Over 90% EQE (external quantum efficiency) was achieved for the solution-processed TV-TmPY-based device compared to that of the vacuum-deposited TmPY at a luminance of 1000 cd m^–2. An EQE deviation of 0.7% was observed ranging from 100 to 1000 cd m^–2 with TV-TmPY, which is the smallest value to date for solution-processed OLEDs, and over 12% EQEs were achieved for the trilayered solution-processed green and blue phosphorescent OLEDs