Design, deposition, and characterization of novel transparent oxide thin films for applications in organic photovoltaics and thin film transistors

Because of the modest conductivity of the widely-used Sn-doped In 2O3 (ITO) films and the soaring In price, transparent oxide conductor (TOC) films with greater conductivity and lower In content are highly desirable. In-doped CdO (CIO)/ITO bilayer TOC films are prepared by combining, in sequence, metal-organic chemical vapor deposition and ion-assisted deposition techniques. Integrating high CIO conductivity with favorable ITO work function and corrosion resistance, these CIO/ITO bilayer TOC films are investigated as anodes in bulk-heterojunction organic photovoltaic (OPV) devices. While the bilayer anode OPVs of the current laboratory size (∼0.06 cm 2) exhibit performance comparable to those of commercial ITO-based control devices, TOC conductivity effect on large-area OPV performance is analyzed through a simulation model and the results reveal significant advantages of using the highly conductive bilayer TOC anodes for large-area OPV cells.;There has been increasing interest in transparent flexible thin film transistors (TF-TFTs) in the past few decades. To achieve high-performance low-operating-voltage TF-TFTs, it is essential to develop and integrate unconventional materials, and design corresponding low-temperature deposition processes. Zinc-Indium-Tin-Oxide (ZITO) films are first grown by pulsed-laser deposition (PLD) using a target with the composition of Zn0.33In1.40 Sn0.27O3. While increasing substrate temperature above 100°C can induce crystallinity, both amorphous ZITO (a-ZITO) TOC and transparent oxide semiconductor (TOS) films can be grown at room temperature by controlling the O2 partial pressure. SiO2-reinforced self-assembled nanodielectric (SR-SAND) is then developed to enhance SAND durability during PLD processes, enabling the combination of SR-SAND with a-ZITO TOS to afford fully transparent TFTs with a high field-effect mobility (muFE) of ∼140 cm2/V˙s at a low operating voltage of ∼1.0 V. Next, a novel concept of all-amorphous-oxide TF-TFTs using the a-ZITO TOS channel is demonstrated with an amorphous Ta2O 5/vapor-deposited SiO2 bilayer dielectric and a-ZITO TOC electrodes. These TF-TFTs composed exclusively of amorphous oxides exhibit great field-effect performance, good transparency, and excellent flexibility. Lastly, a high-performance a-ZITO TOS-based TF-TFT is realized using a high-capacitance vapor-deposited SAND (v-SAND) gate dielectric. A large muFE of ∼110 cm2/V˙s is achieved at an operating voltage of ∼1.0 V. While these TF-TFTs exhibit good visible transparency, bending tests reveal their great mechanical flexibility.