Transparent conducting oxides towards next-generation optoelectronics: Novel function design, thin film growth, and applications in optoelectronic devices

Transparent conducting oxides (TCOs) have drawn extensive attention due to their interesting/unique properties and growing applications for flat panel display, solar energy harvest, and other optoelectronic technologies. With smart designs, TCO thin films possessing more unique properties and functionalities, are capable of reinforcing/broadening their applications in next-generation optoelectronic applications. The goals of the present research are to tailor desirable TCO properties which so far have been scarcely investigated and then implement these demanded thin-film properties into device applications. To this end, the chemical vapor deposition technique (metal-organic chemical vapor deposition, MOCVD) and the physical vapor deposition technique (ion-assisted deposition, IAD) have been utilized to deposit TCO thin films to achieve appropriate functionalities and properties. In the present research, the implementations in optoelectronic devices include the transparent anodes in organic light-emitting diodes (OLEDs), the waveguiding electrodes in organic electro-optical (EO) modulators, and the n-channel semiconducting materials in thin-film transistors (TFTs).; It is quite obvious that multilayer TCO structures have the potential to achieve greater functionality than single-layer TCOs by judicious layer structure design and combining component materials properties. A simple/efficient double-layer strategy has been demonstrated on glass/(In-doped CdO)/ITO and glass/(MgO template layer)/CdO. Especially, (In-doped CdO)/ITO materials have significantly lower sheet resistance than ITO, also rendering them promising electrode materials for large-scale optoelectronic devices. In addition, glass/(In-doped CdO)/ITO-based OLEDs exhibit superior or comparable device performance than ITO control devices.; Highly near-IR transparent TCO films have been developed via manipulation of free charge carrier concentration and minimization of free carrier absorption. Owing to their high transparency and thus very low optical absorption in near-IR region, these highly near-IR transparent TCO films have been successfully implemented as effective electrodes into NIR-sensitive devices (organic EO modulators) and measurement (Teng-Man technique).; High-quality transparent In2O3 thin-film semiconductors have been grown by room-temperature IAD. These In2O3 semiconductors possess high visible-region optical transparency, smooth morphology, and substantial microstructural crystallinity, even when grown at room temperature. Furthermore, high-performance inorganic-organic hybrid TFTs have been fabricated using these In2O3 semiconductors on thin organic dielectrics at near-room temperatures, and the resulting completely transparent inorganic-organic hybrid TFTs exhibit excellent TFT operating characteristics.