Design And Fabrication Of New Transparent Conducting Oxides And Their Applications In Organic Optoelectronics

Transparent conducting oxide (TCO) is an important wide band gap semiconductor and the basic material in the fields of microelectronics, optoelectronics, magnetoelectronics, solar cells, sensors and electrical physics devices. With quickly development of science and technology of thin films, many novel photoelectric devices are developed. Especially, the emergence of organic light-emitting diodes (OLEDs) and organic solar cells (OSCs) stimulates the deep investigation on novel functional thin films and device physics. In this thesis, we develop series of new binary and ternary TCO thin films by modified thermal evaporation deposition and double source reactive electron beam evaporation with End-Hall ion assisted deposited (EHIAD) technologies according to the investigation on the merit and shortcoming of indium tin oxide (ITO) in the application of OLED and OSC. The details are as follows:(1) Two new binary TCO thin films, vanadium and bismuth doped indium oxides (IVO and IBO), are developed by a modified thermal evaporation deposition method. Under unannealed treatment for samples, we investigate the optical and electrical characteristics, and the effects of vanadium and bismuth incorporation on the optical and electrical properties of samples by using Hall measurements, spectrophotometer, Scanning Electron Microscope (SEM), Energy-dispersive X-ray Spectroscopy (EDX) and so on. Our results show that the optical and electrical properties of IVO and IBO samples are comparable to that of commercial ITO. Furthermore, OLEDs based IVO and IBO anodes harvest better performance than the ITO control device.(2) EHIAD techonology is used to deposite two new high work-fucntion ternary TCO coatings, magnesium titanate (MgTiO₃) and praseodymium titanate (PrTiO3)-doped indium oxides (IMTO and IPTO, respectively). Comparing with conventional preparation methods of ternary compound, our technique has a lower cost and the method is beneficial for future industrial manufacture. The surface root-mean-square (RMS) roughnesses of IMTO and IPTO samples have very low values of 0.704 and 1.943 nm, respectively. They are smoother than commercial sputter-derived ITO, which has a RMS roughness of 2.514 nm. All samples demonstrate a high surface work function beyond 5.1 eV, which is comparable to the work function of Au, and much higher than that of commercial ITO. Moreover, the stability of work function of samples is investigated in air. We apply samples as contact anodes to replace ITO in OLEDs, significant improvements in electroluminescence performance for the IMTO and IPTO-anode OLEDs are achieved.(3) A novel high work-function TCO, lanthanum titanate (LaTiO₃)-doped indium oxide (ILTO), with notable electrical and optical features, synthesized by a double electron beam evaporation associated with EHIAD technology is introduced. Its room-temperature ultraviolet photoluminescence (PL) and thermally stable highly effective work function properties are determined. High performance OLEDs and OSCs based on ILTO anodes have been achieved and their effects are discussed in detail.